diff --git a/Makefile b/Makefile
index 565217162b..69eacadf0a 100644
--- a/Makefile
+++ b/Makefile
@@ -86,7 +86,7 @@ endif
 clean:
 	@rm -rf build
 
-FMT_PATHS = ./*.go builder cgo compiler interp ir loader src/device/arm src/examples src/machine src/os src/reflect src/runtime src/sync src/syscall src/internal/reflectlite transform
+FMT_PATHS = ./*.go builder cgo compiler interp loader src/device/arm src/examples src/machine src/os src/reflect src/runtime src/sync src/syscall src/internal/reflectlite transform
 fmt:
 	@gofmt -l -w $(FMT_PATHS)
 fmt-check:
diff --git a/compiler/asserts.go b/compiler/asserts.go
index e8b53f7d46..63f4b90b41 100644
--- a/compiler/asserts.go
+++ b/compiler/asserts.go
@@ -16,7 +16,7 @@ import (
 // slice. This is required by the Go language spec: an index out of bounds must
 // cause a panic.
 func (b *builder) createLookupBoundsCheck(arrayLen, index llvm.Value, indexType types.Type) {
-	if b.fn.IsNoBounds() {
+	if b.info.nobounds {
 		// The //go:nobounds pragma was added to the function to avoid bounds
 		// checking.
 		return
@@ -48,7 +48,7 @@ func (b *builder) createLookupBoundsCheck(arrayLen, index llvm.Value, indexType
 // biggest possible slice capacity, 'low' means len and 'high' means cap. The
 // logic is the same in both cases.
 func (b *builder) createSliceBoundsCheck(capacity, low, high, max llvm.Value, lowType, highType, maxType *types.Basic) {
-	if b.fn.IsNoBounds() {
+	if b.info.nobounds {
 		// The //go:nobounds pragma was added to the function to avoid bounds
 		// checking.
 		return
@@ -104,7 +104,7 @@ func (b *builder) createSliceBoundsCheck(capacity, low, high, max llvm.Value, lo
 // createChanBoundsCheck creates a bounds check before creating a new channel to
 // check that the value is not too big for runtime.chanMake.
 func (b *builder) createChanBoundsCheck(elementSize uint64, bufSize llvm.Value, bufSizeType *types.Basic, pos token.Pos) {
-	if b.fn.IsNoBounds() {
+	if b.info.nobounds {
 		// The //go:nobounds pragma was added to the function to avoid bounds
 		// checking.
 		return
@@ -189,7 +189,7 @@ func (b *builder) createNilCheck(inst ssa.Value, ptr llvm.Value, blockPrefix str
 // createNegativeShiftCheck creates an assertion that panics if the given shift value is negative.
 // This function assumes that the shift value is signed.
 func (b *builder) createNegativeShiftCheck(shift llvm.Value) {
-	if b.fn.IsNoBounds() {
+	if b.info.nobounds {
 		// Function disabled bounds checking - skip shift check.
 		return
 	}
@@ -212,8 +212,8 @@ func (b *builder) createRuntimeAssert(assert llvm.Value, blockPrefix, assertFunc
 		}
 	}
 
-	faultBlock := b.ctx.AddBasicBlock(b.fn.LLVMFn, blockPrefix+".throw")
-	nextBlock := b.ctx.AddBasicBlock(b.fn.LLVMFn, blockPrefix+".next")
+	faultBlock := b.ctx.AddBasicBlock(b.llvmFn, blockPrefix+".throw")
+	nextBlock := b.ctx.AddBasicBlock(b.llvmFn, blockPrefix+".next")
 	b.blockExits[b.currentBlock] = nextBlock // adjust outgoing block for phi nodes
 
 	// Now branch to the out-of-bounds or the regular block.
diff --git a/compiler/calls.go b/compiler/calls.go
index efe96d52d0..87eab60484 100644
--- a/compiler/calls.go
+++ b/compiler/calls.go
@@ -4,6 +4,7 @@ import (
 	"go/types"
 	"strconv"
 
+	"golang.org/x/tools/go/ssa"
 	"tinygo.org/x/go-llvm"
 )
 
@@ -34,14 +35,14 @@ const (
 
 // createCall creates a new call to runtime.<fnName> with the given arguments.
 func (b *builder) createRuntimeCall(fnName string, args []llvm.Value, name string) llvm.Value {
-	fullName := "runtime." + fnName
-	fn := b.mod.NamedFunction(fullName)
-	if fn.IsNil() {
-		panic("trying to call non-existent function: " + fullName)
+	fn := b.program.ImportedPackage("runtime").Members[fnName].(*ssa.Function)
+	llvmFn := b.getFunction(fn)
+	if llvmFn.IsNil() {
+		panic("trying to call non-existent function: " + fn.RelString(nil))
 	}
 	args = append(args, llvm.Undef(b.i8ptrType))            // unused context parameter
 	args = append(args, llvm.ConstPointerNull(b.i8ptrType)) // coroutine handle
-	return b.createCall(fn, args, name)
+	return b.createCall(llvmFn, args, name)
 }
 
 // createCall creates a call to the given function with the arguments possibly
diff --git a/compiler/compiler.go b/compiler/compiler.go
index c5b7be6581..745d2ad2cb 100644
--- a/compiler/compiler.go
+++ b/compiler/compiler.go
@@ -15,7 +15,6 @@ import (
 
 	"github.com/tinygo-org/tinygo/compileopts"
 	"github.com/tinygo-org/tinygo/compiler/llvmutil"
-	"github.com/tinygo-org/tinygo/ir"
 	"github.com/tinygo-org/tinygo/loader"
 	"golang.org/x/tools/go/ssa"
 	"tinygo.org/x/go-llvm"
@@ -49,7 +48,7 @@ type compilerContext struct {
 	i8ptrType        llvm.Type // for convenience
 	funcPtrAddrSpace int
 	uintptrType      llvm.Type
-	ir               *ir.Program
+	program          *ssa.Program
 	diagnostics      []error
 	astComments      map[string]*ast.CommentGroup
 }
@@ -97,7 +96,9 @@ func newCompilerContext(moduleName string, machine llvm.TargetMachine, config *c
 type builder struct {
 	*compilerContext
 	llvm.Builder
-	fn                *ir.Function
+	fn                *ssa.Function
+	llvmFn            llvm.Value
+	info              functionInfo
 	locals            map[ssa.Value]llvm.Value            // local variables
 	blockEntries      map[*ssa.BasicBlock]llvm.BasicBlock // a *ssa.BasicBlock may be split up
 	blockExits        map[*ssa.BasicBlock]llvm.BasicBlock // these are the exit blocks
@@ -108,19 +109,21 @@ type builder struct {
 	difunc            llvm.Metadata
 	dilocals          map[*types.Var]llvm.Metadata
 	allDeferFuncs     []interface{}
-	deferFuncs        map[*ir.Function]int
+	deferFuncs        map[*ssa.Function]int
 	deferInvokeFuncs  map[string]int
-	deferClosureFuncs map[*ir.Function]int
+	deferClosureFuncs map[*ssa.Function]int
 	deferExprFuncs    map[ssa.Value]int
 	selectRecvBuf     map[*ssa.Select]llvm.Value
 	deferBuiltinFuncs map[ssa.Value]deferBuiltin
 }
 
-func newBuilder(c *compilerContext, irbuilder llvm.Builder, f *ir.Function) *builder {
+func newBuilder(c *compilerContext, irbuilder llvm.Builder, f *ssa.Function) *builder {
 	return &builder{
 		compilerContext: c,
 		Builder:         irbuilder,
 		fn:              f,
+		llvmFn:          c.getFunction(f),
+		info:            c.getFunctionInfo(f),
 		locals:          make(map[ssa.Value]llvm.Value),
 		dilocals:        make(map[*types.Var]llvm.Metadata),
 		blockEntries:    make(map[*ssa.BasicBlock]llvm.BasicBlock),
@@ -214,10 +217,11 @@ func Sizes(machine llvm.TargetMachine) types.Sizes {
 func CompileProgram(pkgName string, lprogram *loader.Program, machine llvm.TargetMachine, config *compileopts.Config) (llvm.Module, []error) {
 	c := newCompilerContext(pkgName, machine, config)
 
-	c.ir = ir.NewProgram(lprogram)
+	c.program = lprogram.LoadSSA()
+	c.program.Build()
 
 	// Run a simple dead code elimination pass.
-	err := c.ir.SimpleDCE()
+	functions, err := c.simpleDCE(lprogram)
 	if err != nil {
 		return llvm.Module{}, []error{err}
 	}
@@ -239,7 +243,7 @@ func CompileProgram(pkgName string, lprogram *loader.Program, machine llvm.Targe
 	// TODO: lazily create runtime types in getLLVMRuntimeType when they are
 	// needed. Eventually this will be required anyway, when packages are
 	// compiled independently (and the runtime types are not available).
-	for _, member := range c.ir.Program.ImportedPackage("runtime").Members {
+	for _, member := range c.program.ImportedPackage("runtime").Members {
 		if member, ok := member.(*ssa.Type); ok {
 			if typ, ok := member.Type().(*types.Named); ok {
 				if _, ok := typ.Underlying().(*types.Struct); ok {
@@ -249,21 +253,17 @@ func CompileProgram(pkgName string, lprogram *loader.Program, machine llvm.Targe
 		}
 	}
 
-	// Declare all functions.
-	for _, f := range c.ir.Functions {
-		c.createFunctionDeclaration(f)
-	}
+	// Predeclare the runtime.alloc function, which is used by the wordpack
+	// functionality.
+	c.getFunction(c.program.ImportedPackage("runtime").Members["alloc"].(*ssa.Function))
 
 	// Add definitions to declarations.
 	var initFuncs []llvm.Value
 	irbuilder := c.ctx.NewBuilder()
 	defer irbuilder.Dispose()
-	for _, f := range c.ir.Functions {
+	for _, f := range functions {
 		if f.Synthetic == "package initializer" {
-			initFuncs = append(initFuncs, f.LLVMFn)
-		}
-		if f.CName() != "" {
-			continue
+			initFuncs = append(initFuncs, c.getFunction(f))
 		}
 		if f.Blocks == nil {
 			continue // external function
@@ -271,22 +271,23 @@ func CompileProgram(pkgName string, lprogram *loader.Program, machine llvm.Targe
 
 		// Create the function definition.
 		b := newBuilder(c, irbuilder, f)
-		b.createFunctionDefinition()
+		b.createFunction()
 	}
 
 	// After all packages are imported, add a synthetic initializer function
 	// that calls the initializer of each package.
-	initFn := c.ir.GetFunction(c.ir.Program.ImportedPackage("runtime").Members["initAll"].(*ssa.Function))
-	initFn.LLVMFn.SetLinkage(llvm.InternalLinkage)
-	initFn.LLVMFn.SetUnnamedAddr(true)
+	initFn := c.program.ImportedPackage("runtime").Members["initAll"].(*ssa.Function)
+	llvmInitFn := c.getFunction(initFn)
+	llvmInitFn.SetLinkage(llvm.InternalLinkage)
+	llvmInitFn.SetUnnamedAddr(true)
 	if c.Debug() {
 		difunc := c.attachDebugInfo(initFn)
-		pos := c.ir.Program.Fset.Position(initFn.Pos())
+		pos := c.program.Fset.Position(initFn.Pos())
 		irbuilder.SetCurrentDebugLocation(uint(pos.Line), uint(pos.Column), difunc, llvm.Metadata{})
 	}
-	initFn.LLVMFn.Param(0).SetName("context")
-	initFn.LLVMFn.Param(1).SetName("parentHandle")
-	block := c.ctx.AddBasicBlock(initFn.LLVMFn, "entry")
+	llvmInitFn.Param(0).SetName("context")
+	llvmInitFn.Param(1).SetName("parentHandle")
+	block := c.ctx.AddBasicBlock(llvmInitFn, "entry")
 	irbuilder.SetInsertPointAtEnd(block)
 	for _, fn := range initFuncs {
 		irbuilder.CreateCall(fn, []llvm.Value{llvm.Undef(c.i8ptrType), llvm.Undef(c.i8ptrType)}, "")
@@ -295,7 +296,7 @@ func CompileProgram(pkgName string, lprogram *loader.Program, machine llvm.Targe
 
 	// Conserve for goroutine lowering. Without marking these as external, they
 	// would be optimized away.
-	realMain := c.mod.NamedFunction(c.ir.MainPkg().Pkg.Path() + ".main")
+	realMain := c.mod.NamedFunction(lprogram.MainPkg().Pkg.Path() + ".main")
 	realMain.SetLinkage(llvm.ExternalLinkage) // keep alive until goroutine lowering
 
 	// Replace callMain placeholder with actual main function.
@@ -377,33 +378,20 @@ func CompilePackage(moduleName string, pkg *loader.Package, machine llvm.TargetM
 		return iPos < jPos
 	})
 
-	// Create *ir.Functions objects.
-	var functions []*ir.Function
+	// Define all functions.
+	irbuilder := c.ctx.NewBuilder()
+	defer irbuilder.Dispose()
 	for _, name := range members {
 		member := ssaPkg.Members[name]
 		switch member := member.(type) {
 		case *ssa.Function:
-			functions = append(functions, &ir.Function{
-				Function: member,
-			})
-		}
-	}
-
-	// Declare all functions.
-	for _, fn := range functions {
-		c.createFunctionDeclaration(fn)
-	}
-
-	// Add definitions to declarations.
-	irbuilder := c.ctx.NewBuilder()
-	defer irbuilder.Dispose()
-	for _, f := range functions {
-		if f.Blocks == nil {
-			continue // external function
+			if member.Blocks == nil {
+				continue // external function
+			}
+			// Create the function definition.
+			b := newBuilder(c, irbuilder, member)
+			b.createFunction()
 		}
-		// Create the function definition.
-		b := newBuilder(c, irbuilder, f)
-		b.createFunctionDefinition()
 	}
 
 	return c.mod, nil
@@ -602,11 +590,11 @@ func (c *compilerContext) createDIType(typ types.Type) llvm.Metadata {
 			Encoding:   encoding,
 		})
 	case *types.Chan:
-		return c.getDIType(types.NewPointer(c.ir.Program.ImportedPackage("runtime").Members["channel"].(*ssa.Type).Type()))
+		return c.getDIType(types.NewPointer(c.program.ImportedPackage("runtime").Members["channel"].(*ssa.Type).Type()))
 	case *types.Interface:
-		return c.getDIType(c.ir.Program.ImportedPackage("runtime").Members["_interface"].(*ssa.Type).Type())
+		return c.getDIType(c.program.ImportedPackage("runtime").Members["_interface"].(*ssa.Type).Type())
 	case *types.Map:
-		return c.getDIType(types.NewPointer(c.ir.Program.ImportedPackage("runtime").Members["hashmap"].(*ssa.Type).Type()))
+		return c.getDIType(types.NewPointer(c.program.ImportedPackage("runtime").Members["hashmap"].(*ssa.Type).Type()))
 	case *types.Named:
 		return c.dibuilder.CreateTypedef(llvm.DITypedef{
 			Type: c.getDIType(typ.Underlying()),
@@ -714,7 +702,7 @@ func (b *builder) getLocalVariable(variable *types.Var) llvm.Metadata {
 		return dilocal
 	}
 
-	pos := b.ir.Program.Fset.Position(variable.Pos())
+	pos := b.program.Fset.Position(variable.Pos())
 
 	// Check whether this is a function parameter.
 	for i, param := range b.fn.Params {
@@ -745,95 +733,17 @@ func (b *builder) getLocalVariable(variable *types.Var) llvm.Metadata {
 	return dilocal
 }
 
-// createFunctionDeclaration creates a LLVM function declaration without body.
-// It can later be filled with frame.createFunctionDefinition().
-func (c *compilerContext) createFunctionDeclaration(f *ir.Function) {
-	var retType llvm.Type
-	if f.Signature.Results() == nil {
-		retType = c.ctx.VoidType()
-	} else if f.Signature.Results().Len() == 1 {
-		retType = c.getLLVMType(f.Signature.Results().At(0).Type())
-	} else {
-		results := make([]llvm.Type, 0, f.Signature.Results().Len())
-		for i := 0; i < f.Signature.Results().Len(); i++ {
-			results = append(results, c.getLLVMType(f.Signature.Results().At(i).Type()))
-		}
-		retType = c.ctx.StructType(results, false)
-	}
-
-	var paramInfos []paramInfo
-	for _, param := range f.Params {
-		paramType := c.getLLVMType(param.Type())
-		paramFragmentInfos := expandFormalParamType(paramType, param.Name(), param.Type())
-		paramInfos = append(paramInfos, paramFragmentInfos...)
-	}
-
-	// Add an extra parameter as the function context. This context is used in
-	// closures and bound methods, but should be optimized away when not used.
-	if !f.IsExported() {
-		paramInfos = append(paramInfos, paramInfo{llvmType: c.i8ptrType, name: "context", flags: 0})
-		paramInfos = append(paramInfos, paramInfo{llvmType: c.i8ptrType, name: "parentHandle", flags: 0})
-	}
-
-	var paramTypes []llvm.Type
-	for _, info := range paramInfos {
-		paramTypes = append(paramTypes, info.llvmType)
-	}
-
-	fnType := llvm.FunctionType(retType, paramTypes, false)
-
-	name := f.LinkName()
-	f.LLVMFn = c.mod.NamedFunction(name)
-	if f.LLVMFn.IsNil() {
-		f.LLVMFn = llvm.AddFunction(c.mod, name, fnType)
-	}
-
-	dereferenceableOrNullKind := llvm.AttributeKindID("dereferenceable_or_null")
-	for i, info := range paramInfos {
-		if info.flags&paramIsDeferenceableOrNull == 0 {
-			continue
-		}
-		if info.llvmType.TypeKind() == llvm.PointerTypeKind {
-			el := info.llvmType.ElementType()
-			size := c.targetData.TypeAllocSize(el)
-			if size == 0 {
-				// dereferenceable_or_null(0) appears to be illegal in LLVM.
-				continue
-			}
-			dereferenceableOrNull := c.ctx.CreateEnumAttribute(dereferenceableOrNullKind, size)
-			f.LLVMFn.AddAttributeAtIndex(i+1, dereferenceableOrNull)
-		}
-	}
-
-	// External/exported functions may not retain pointer values.
-	// https://golang.org/cmd/cgo/#hdr-Passing_pointers
-	if f.IsExported() {
-		// Set the wasm-import-module attribute if the function's module is set.
-		if f.Module() != "" {
-			wasmImportModuleAttr := c.ctx.CreateStringAttribute("wasm-import-module", f.Module())
-			f.LLVMFn.AddFunctionAttr(wasmImportModuleAttr)
-		}
-		nocaptureKind := llvm.AttributeKindID("nocapture")
-		nocapture := c.ctx.CreateEnumAttribute(nocaptureKind, 0)
-		for i, typ := range paramTypes {
-			if typ.TypeKind() == llvm.PointerTypeKind {
-				f.LLVMFn.AddAttributeAtIndex(i+1, nocapture)
-			}
-		}
-	}
-}
-
 // attachDebugInfo adds debug info to a function declaration. It returns the
 // DISubprogram metadata node.
-func (c *compilerContext) attachDebugInfo(f *ir.Function) llvm.Metadata {
-	pos := c.ir.Program.Fset.Position(f.Syntax().Pos())
-	return c.attachDebugInfoRaw(f, f.LLVMFn, "", pos.Filename, pos.Line)
+func (c *compilerContext) attachDebugInfo(f *ssa.Function) llvm.Metadata {
+	pos := c.program.Fset.Position(f.Syntax().Pos())
+	return c.attachDebugInfoRaw(f, c.getFunction(f), "", pos.Filename, pos.Line)
 }
 
 // attachDebugInfo adds debug info to a function declaration. It returns the
 // DISubprogram metadata node. This method allows some more control over how
 // debug info is added to the function.
-func (c *compilerContext) attachDebugInfoRaw(f *ir.Function, llvmFn llvm.Value, suffix, filename string, line int) llvm.Metadata {
+func (c *compilerContext) attachDebugInfoRaw(f *ssa.Function, llvmFn llvm.Value, suffix, filename string, line int) llvm.Metadata {
 	// Debug info for this function.
 	diparams := make([]llvm.Metadata, 0, len(f.Params))
 	for _, param := range f.Params {
@@ -846,7 +756,7 @@ func (c *compilerContext) attachDebugInfoRaw(f *ir.Function, llvmFn llvm.Value,
 	})
 	difunc := c.dibuilder.CreateFunction(c.getDIFile(filename), llvm.DIFunction{
 		Name:         f.RelString(nil) + suffix,
-		LinkageName:  f.LinkName() + suffix,
+		LinkageName:  c.getFunctionInfo(f).linkName + suffix,
 		File:         c.getDIFile(filename),
 		Line:         line,
 		Type:         diFuncType,
@@ -874,37 +784,37 @@ func (c *compilerContext) getDIFile(filename string) llvm.Metadata {
 	return c.difiles[filename]
 }
 
-// createFunctionDefinition builds the LLVM IR implementation for this function.
-// The function must be declared but not yet defined, otherwise this function
-// will create a diagnostic.
-func (b *builder) createFunctionDefinition() {
+// createFunction builds the LLVM IR implementation for this function. The
+// function must not yet be defined, otherwise this function will create a
+// diagnostic.
+func (b *builder) createFunction() {
 	if b.DumpSSA() {
-		fmt.Printf("\nfunc %s:\n", b.fn.Function)
+		fmt.Printf("\nfunc %s:\n", b.fn)
 	}
-	if !b.fn.LLVMFn.IsDeclaration() {
+	if !b.llvmFn.IsDeclaration() {
 		errValue := b.fn.Name() + " redeclared in this program"
-		fnPos := getPosition(b.fn.LLVMFn)
+		fnPos := getPosition(b.llvmFn)
 		if fnPos.IsValid() {
 			errValue += "\n\tprevious declaration at " + fnPos.String()
 		}
 		b.addError(b.fn.Pos(), errValue)
 		return
 	}
-	if !b.fn.IsExported() {
-		b.fn.LLVMFn.SetLinkage(llvm.InternalLinkage)
-		b.fn.LLVMFn.SetUnnamedAddr(true)
+	if !b.info.exported {
+		b.llvmFn.SetLinkage(llvm.InternalLinkage)
+		b.llvmFn.SetUnnamedAddr(true)
 	}
 
 	// Some functions have a pragma controlling the inlining level.
-	switch b.fn.Inline() {
-	case ir.InlineHint:
+	switch b.info.inline {
+	case inlineHint:
 		// Add LLVM inline hint to functions with //go:inline pragma.
 		inline := b.ctx.CreateEnumAttribute(llvm.AttributeKindID("inlinehint"), 0)
-		b.fn.LLVMFn.AddFunctionAttr(inline)
-	case ir.InlineNone:
+		b.llvmFn.AddFunctionAttr(inline)
+	case inlineNone:
 		// Add LLVM attribute to always avoid inlining this function.
 		noinline := b.ctx.CreateEnumAttribute(llvm.AttributeKindID("noinline"), 0)
-		b.fn.LLVMFn.AddFunctionAttr(noinline)
+		b.llvmFn.AddFunctionAttr(noinline)
 	}
 
 	// Add debug info, if needed.
@@ -913,18 +823,18 @@ func (b *builder) createFunctionDefinition() {
 			// Package initializers have no debug info. Create some fake debug
 			// info to at least have *something*.
 			filename := b.fn.Package().Pkg.Path() + "/<init>"
-			b.difunc = b.attachDebugInfoRaw(b.fn, b.fn.LLVMFn, "", filename, 0)
+			b.difunc = b.attachDebugInfoRaw(b.fn, b.llvmFn, "", filename, 0)
 		} else if b.fn.Syntax() != nil {
 			// Create debug info file if needed.
 			b.difunc = b.attachDebugInfo(b.fn)
 		}
-		pos := b.ir.Program.Fset.Position(b.fn.Pos())
+		pos := b.program.Fset.Position(b.fn.Pos())
 		b.SetCurrentDebugLocation(uint(pos.Line), uint(pos.Column), b.difunc, llvm.Metadata{})
 	}
 
 	// Pre-create all basic blocks in the function.
 	for _, block := range b.fn.DomPreorder() {
-		llvmBlock := b.ctx.AddBasicBlock(b.fn.LLVMFn, block.Comment)
+		llvmBlock := b.ctx.AddBasicBlock(b.llvmFn, block.Comment)
 		b.blockEntries[block] = llvmBlock
 		b.blockExits[block] = llvmBlock
 	}
@@ -937,7 +847,7 @@ func (b *builder) createFunctionDefinition() {
 		llvmType := b.getLLVMType(param.Type())
 		fields := make([]llvm.Value, 0, 1)
 		for _, info := range expandFormalParamType(llvmType, param.Name(), param.Type()) {
-			param := b.fn.LLVMFn.Param(llvmParamIndex)
+			param := b.llvmFn.Param(llvmParamIndex)
 			param.SetName(info.name)
 			fields = append(fields, param)
 			llvmParamIndex++
@@ -968,8 +878,8 @@ func (b *builder) createFunctionDefinition() {
 	// Load free variables from the context. This is a closure (or bound
 	// method).
 	var context llvm.Value
-	if !b.fn.IsExported() {
-		parentHandle := b.fn.LLVMFn.LastParam()
+	if !b.info.exported {
+		parentHandle := b.llvmFn.LastParam()
 		parentHandle.SetName("parentHandle")
 		context = llvm.PrevParam(parentHandle)
 		context.SetName("context")
@@ -1020,7 +930,7 @@ func (b *builder) createFunctionDefinition() {
 					continue
 				}
 				dbgVar := b.getLocalVariable(variable)
-				pos := b.ir.Program.Fset.Position(instr.Pos())
+				pos := b.program.Fset.Position(instr.Pos())
 				b.dibuilder.InsertValueAtEnd(b.getValue(instr.X), dbgVar, b.dibuilder.CreateExpression(nil), llvm.DebugLoc{
 					Line:  uint(pos.Line),
 					Col:   uint(pos.Column),
@@ -1069,7 +979,7 @@ func (b *builder) createFunctionDefinition() {
 // particular Go SSA instruction.
 func (b *builder) createInstruction(instr ssa.Instruction) {
 	if b.Debug() {
-		pos := b.ir.Program.Fset.Position(instr.Pos())
+		pos := b.program.Fset.Position(instr.Pos())
 		b.SetCurrentDebugLocation(uint(pos.Line), uint(pos.Column), b.difunc, llvm.Metadata{})
 	}
 
@@ -1105,7 +1015,6 @@ func (b *builder) createInstruction(instr ssa.Instruction) {
 		if callee := instr.Call.StaticCallee(); callee != nil {
 			// Static callee is known. This makes it easier to start a new
 			// goroutine.
-			calleeFn := b.ir.GetFunction(callee)
 			var context llvm.Value
 			switch value := instr.Call.Value.(type) {
 			case *ssa.Function:
@@ -1120,7 +1029,7 @@ func (b *builder) createInstruction(instr ssa.Instruction) {
 				panic("StaticCallee returned an unexpected value")
 			}
 			params = append(params, context) // context parameter
-			b.createGoInstruction(calleeFn.LLVMFn, params, "", callee.Pos())
+			b.createGoInstruction(b.getFunction(callee), params, "", callee.Pos())
 		} else if !instr.Call.IsInvoke() {
 			// This is a function pointer.
 			// At the moment, two extra params are passed to the newly started
@@ -1168,7 +1077,7 @@ func (b *builder) createInstruction(instr ssa.Instruction) {
 			b.CreateRet(b.getValue(instr.Results[0]))
 		} else {
 			// Multiple return values. Put them all in a struct.
-			retVal := llvm.ConstNull(b.fn.LLVMFn.Type().ElementType().ReturnType())
+			retVal := llvm.ConstNull(b.llvmFn.Type().ElementType().ReturnType())
 			for i, result := range instr.Results {
 				val := b.getValue(result)
 				retVal = b.CreateInsertValue(retVal, val, i, "")
@@ -1411,9 +1320,10 @@ func (b *builder) createFunctionCall(instr *ssa.CallCommon) (llvm.Value, error)
 			return b.createInterruptGlobal(instr)
 		}
 
-		targetFunc := b.ir.GetFunction(fn)
-		if targetFunc.LLVMFn.IsNil() {
-			return llvm.Value{}, b.makeError(instr.Pos(), "undefined function: "+targetFunc.LinkName())
+		callee = b.getFunction(fn)
+		info := b.getFunctionInfo(fn)
+		if callee.IsNil() {
+			return llvm.Value{}, b.makeError(instr.Pos(), "undefined function: "+info.linkName)
 		}
 		switch value := instr.Value.(type) {
 		case *ssa.Function:
@@ -1427,8 +1337,7 @@ func (b *builder) createFunctionCall(instr *ssa.CallCommon) (llvm.Value, error)
 		default:
 			panic("StaticCallee returned an unexpected value")
 		}
-		callee = targetFunc.LLVMFn
-		exported = targetFunc.IsExported()
+		exported = info.exported
 	} else if call, ok := instr.Value.(*ssa.Builtin); ok {
 		// Builtin function (append, close, delete, etc.).)
 		return b.createBuiltin(instr.Args, call.Name(), instr.Pos())
@@ -1463,14 +1372,13 @@ func (b *builder) createFunctionCall(instr *ssa.CallCommon) (llvm.Value, error)
 func (b *builder) getValue(expr ssa.Value) llvm.Value {
 	switch expr := expr.(type) {
 	case *ssa.Const:
-		return b.createConst(b.fn.LinkName(), expr)
+		return b.createConst(b.info.linkName, expr)
 	case *ssa.Function:
-		fn := b.ir.GetFunction(expr)
-		if fn.IsExported() {
+		if b.getFunctionInfo(expr).exported {
 			b.addError(expr.Pos(), "cannot use an exported function as value: "+expr.String())
 			return llvm.Undef(b.getLLVMType(expr.Type()))
 		}
-		return b.createFuncValue(fn.LLVMFn, llvm.Undef(b.i8ptrType), fn.Signature)
+		return b.createFuncValue(b.getFunction(expr), llvm.Undef(b.i8ptrType), expr.Signature)
 	case *ssa.Global:
 		value := b.getGlobal(expr)
 		if value.IsNil() {
@@ -2658,7 +2566,7 @@ func (b *builder) createUnOp(unop *ssa.UnOp) (llvm.Value, error) {
 			// function pointer itself.
 			globalName := b.getGlobalInfo(unop.X.(*ssa.Global)).linkName
 			name := globalName[:len(globalName)-len("$funcaddr")]
-			fn := b.mod.NamedFunction(name)
+			fn := b.getFunction(b.fn.Pkg.Members["C."+name].(*ssa.Function))
 			if fn.IsNil() {
 				return llvm.Value{}, b.makeError(unop.Pos(), "cgo function not found: "+name)
 			}
diff --git a/compiler/defer.go b/compiler/defer.go
index db2bed3282..5ebbf7db1d 100644
--- a/compiler/defer.go
+++ b/compiler/defer.go
@@ -14,9 +14,9 @@ package compiler
 //     frames.
 
 import (
-	"github.com/tinygo-org/tinygo/compiler/llvmutil"
-	"github.com/tinygo-org/tinygo/ir"
 	"go/types"
+
+	"github.com/tinygo-org/tinygo/compiler/llvmutil"
 	"golang.org/x/tools/go/ssa"
 	"tinygo.org/x/go-llvm"
 )
@@ -26,9 +26,9 @@ import (
 // calls.
 func (b *builder) deferInitFunc() {
 	// Some setup.
-	b.deferFuncs = make(map[*ir.Function]int)
+	b.deferFuncs = make(map[*ssa.Function]int)
 	b.deferInvokeFuncs = make(map[string]int)
-	b.deferClosureFuncs = make(map[*ir.Function]int)
+	b.deferClosureFuncs = make(map[*ssa.Function]int)
 	b.deferExprFuncs = make(map[ssa.Value]int)
 	b.deferBuiltinFuncs = make(map[ssa.Value]deferBuiltin)
 
@@ -107,13 +107,11 @@ func (b *builder) createDefer(instr *ssa.Defer) {
 
 	} else if callee, ok := instr.Call.Value.(*ssa.Function); ok {
 		// Regular function call.
-		fn := b.ir.GetFunction(callee)
-
-		if _, ok := b.deferFuncs[fn]; !ok {
-			b.deferFuncs[fn] = len(b.allDeferFuncs)
-			b.allDeferFuncs = append(b.allDeferFuncs, fn)
+		if _, ok := b.deferFuncs[callee]; !ok {
+			b.deferFuncs[callee] = len(b.allDeferFuncs)
+			b.allDeferFuncs = append(b.allDeferFuncs, callee)
 		}
-		callback := llvm.ConstInt(b.uintptrType, uint64(b.deferFuncs[fn]), false)
+		callback := llvm.ConstInt(b.uintptrType, uint64(b.deferFuncs[callee]), false)
 
 		// Collect all values to be put in the struct (starting with
 		// runtime._defer fields).
@@ -135,7 +133,7 @@ func (b *builder) createDefer(instr *ssa.Defer) {
 		context := b.CreateExtractValue(closure, 0, "")
 
 		// Get the callback number.
-		fn := b.ir.GetFunction(makeClosure.Fn.(*ssa.Function))
+		fn := makeClosure.Fn.(*ssa.Function)
 		if _, ok := b.deferClosureFuncs[fn]; !ok {
 			b.deferClosureFuncs[fn] = len(b.allDeferFuncs)
 			b.allDeferFuncs = append(b.allDeferFuncs, makeClosure)
@@ -251,10 +249,10 @@ func (b *builder) createRunDefers() {
 	//     }
 
 	// Create loop.
-	loophead := b.ctx.AddBasicBlock(b.fn.LLVMFn, "rundefers.loophead")
-	loop := b.ctx.AddBasicBlock(b.fn.LLVMFn, "rundefers.loop")
-	unreachable := b.ctx.AddBasicBlock(b.fn.LLVMFn, "rundefers.default")
-	end := b.ctx.AddBasicBlock(b.fn.LLVMFn, "rundefers.end")
+	loophead := b.ctx.AddBasicBlock(b.llvmFn, "rundefers.loophead")
+	loop := b.ctx.AddBasicBlock(b.llvmFn, "rundefers.loop")
+	unreachable := b.ctx.AddBasicBlock(b.llvmFn, "rundefers.default")
+	end := b.ctx.AddBasicBlock(b.llvmFn, "rundefers.end")
 	b.CreateBr(loophead)
 
 	// Create loop head:
@@ -286,7 +284,7 @@ func (b *builder) createRunDefers() {
 		// Create switch case, for example:
 		//     case 0:
 		//         // run first deferred call
-		block := b.ctx.AddBasicBlock(b.fn.LLVMFn, "rundefers.callback")
+		block := b.ctx.AddBasicBlock(b.llvmFn, "rundefers.callback")
 		sw.AddCase(llvm.ConstInt(b.uintptrType, uint64(i), false), block)
 		b.SetInsertPointAtEnd(block)
 		switch callback := callback.(type) {
@@ -350,7 +348,7 @@ func (b *builder) createRunDefers() {
 
 			b.createCall(fnPtr, forwardParams, "")
 
-		case *ir.Function:
+		case *ssa.Function:
 			// Direct call.
 
 			// Get the real defer struct type and cast to it.
@@ -372,7 +370,7 @@ func (b *builder) createRunDefers() {
 
 			// Plain TinyGo functions add some extra parameters to implement async functionality and function recievers.
 			// These parameters should not be supplied when calling into an external C/ASM function.
-			if !callback.IsExported() {
+			if !b.getFunctionInfo(callback).exported {
 				// Add the context parameter. We know it is ignored by the receiving
 				// function, but we have to pass one anyway.
 				forwardParams = append(forwardParams, llvm.Undef(b.i8ptrType))
@@ -382,11 +380,11 @@ func (b *builder) createRunDefers() {
 			}
 
 			// Call real function.
-			b.createCall(callback.LLVMFn, forwardParams, "")
+			b.createCall(b.getFunction(callback), forwardParams, "")
 
 		case *ssa.MakeClosure:
 			// Get the real defer struct type and cast to it.
-			fn := b.ir.GetFunction(callback.Fn.(*ssa.Function))
+			fn := callback.Fn.(*ssa.Function)
 			valueTypes := []llvm.Type{b.uintptrType, llvm.PointerType(b.getLLVMRuntimeType("_defer"), 0)}
 			params := fn.Signature.Params()
 			for i := 0; i < params.Len(); i++ {
@@ -409,7 +407,7 @@ func (b *builder) createRunDefers() {
 			forwardParams = append(forwardParams, llvm.Undef(b.i8ptrType))
 
 			// Call deferred function.
-			b.createCall(fn.LLVMFn, forwardParams, "")
+			b.createCall(b.getFunction(fn), forwardParams, "")
 		case *ssa.Builtin:
 			db := b.deferBuiltinFuncs[callback]
 
diff --git a/compiler/errors.go b/compiler/errors.go
index 85de4d161e..1181322980 100644
--- a/compiler/errors.go
+++ b/compiler/errors.go
@@ -14,7 +14,7 @@ import (
 // makeError makes it easy to create an error from a token.Pos with a message.
 func (c *compilerContext) makeError(pos token.Pos, msg string) types.Error {
 	return types.Error{
-		Fset: c.ir.Program.Fset,
+		Fset: c.program.Fset,
 		Pos:  pos,
 		Msg:  msg,
 	}
diff --git a/compiler/func.go b/compiler/func.go
index 463350aaae..7f5e4398d3 100644
--- a/compiler/func.go
+++ b/compiler/func.go
@@ -149,7 +149,7 @@ func (b *builder) parseMakeClosure(expr *ssa.MakeClosure) (llvm.Value, error) {
 	if len(expr.Bindings) == 0 {
 		panic("unexpected: MakeClosure without bound variables")
 	}
-	f := b.ir.GetFunction(expr.Fn.(*ssa.Function))
+	f := expr.Fn.(*ssa.Function)
 
 	// Collect all bound variables.
 	boundVars := make([]llvm.Value, len(expr.Bindings))
@@ -164,5 +164,5 @@ func (b *builder) parseMakeClosure(expr *ssa.MakeClosure) (llvm.Value, error) {
 	context := b.emitPointerPack(boundVars)
 
 	// Create the closure.
-	return b.createFuncValue(f.LLVMFn, context, f.Signature), nil
+	return b.createFuncValue(b.getFunction(f), context, f.Signature), nil
 }
diff --git a/compiler/goroutine.go b/compiler/goroutine.go
index 23978ccb24..2afa5b0149 100644
--- a/compiler/goroutine.go
+++ b/compiler/goroutine.go
@@ -7,6 +7,7 @@ import (
 	"go/token"
 
 	"github.com/tinygo-org/tinygo/compiler/llvmutil"
+	"golang.org/x/tools/go/ssa"
 	"tinygo.org/x/go-llvm"
 )
 
@@ -28,7 +29,8 @@ func (b *builder) createGoInstruction(funcPtr llvm.Value, params []llvm.Value, p
 			// function that will be replaced with a load from a special ELF
 			// section that contains the stack size (and is modified after
 			// linking).
-			stackSize = b.createCall(b.mod.NamedFunction("internal/task.getGoroutineStackSize"), []llvm.Value{callee, llvm.Undef(b.i8ptrType), llvm.Undef(b.i8ptrType)}, "stacksize")
+			stackSizeFn := b.getFunction(b.program.ImportedPackage("internal/task").Members["getGoroutineStackSize"].(*ssa.Function))
+			stackSize = b.createCall(stackSizeFn, []llvm.Value{callee, llvm.Undef(b.i8ptrType), llvm.Undef(b.i8ptrType)}, "stacksize")
 		} else {
 			// The stack size is fixed at compile time. By emitting it here as a
 			// constant, it can be optimized.
@@ -42,7 +44,8 @@ func (b *builder) createGoInstruction(funcPtr llvm.Value, params []llvm.Value, p
 	default:
 		panic("unreachable")
 	}
-	b.createCall(b.mod.NamedFunction("internal/task.start"), []llvm.Value{callee, paramBundle, stackSize, llvm.Undef(b.i8ptrType), llvm.ConstPointerNull(b.i8ptrType)}, "")
+	start := b.getFunction(b.program.ImportedPackage("internal/task").Members["start"].(*ssa.Function))
+	b.createCall(start, []llvm.Value{callee, paramBundle, stackSize, llvm.Undef(b.i8ptrType), llvm.ConstPointerNull(b.i8ptrType)}, "")
 	return llvm.Undef(funcPtr.Type().ElementType().ReturnType())
 }
 
@@ -88,7 +91,7 @@ func (c *compilerContext) createGoroutineStartWrapper(fn llvm.Value, prefix stri
 		builder.SetInsertPointAtEnd(entry)
 
 		if c.Debug() {
-			pos := c.ir.Program.Fset.Position(pos)
+			pos := c.program.Fset.Position(pos)
 			diFuncType := c.dibuilder.CreateSubroutineType(llvm.DISubroutineType{
 				File:       c.getDIFile(pos.Filename),
 				Parameters: nil, // do not show parameters in debugger
@@ -145,7 +148,7 @@ func (c *compilerContext) createGoroutineStartWrapper(fn llvm.Value, prefix stri
 		builder.SetInsertPointAtEnd(entry)
 
 		if c.Debug() {
-			pos := c.ir.Program.Fset.Position(pos)
+			pos := c.program.Fset.Position(pos)
 			diFuncType := c.dibuilder.CreateSubroutineType(llvm.DISubroutineType{
 				File:       c.getDIFile(pos.Filename),
 				Parameters: nil, // do not show parameters in debugger
diff --git a/compiler/interface.go b/compiler/interface.go
index 030c67571b..24986dd143 100644
--- a/compiler/interface.go
+++ b/compiler/interface.go
@@ -11,7 +11,6 @@ import (
 	"strconv"
 	"strings"
 
-	"github.com/tinygo-org/tinygo/ir"
 	"golang.org/x/tools/go/ssa"
 	"tinygo.org/x/go-llvm"
 )
@@ -236,7 +235,7 @@ func (c *compilerContext) getTypeMethodSet(typ types.Type) llvm.Value {
 		return llvm.ConstGEP(global, []llvm.Value{zero, zero})
 	}
 
-	ms := c.ir.Program.MethodSets.MethodSet(typ)
+	ms := c.program.MethodSets.MethodSet(typ)
 	if ms.Len() == 0 {
 		// no methods, so can leave that one out
 		return llvm.ConstPointerNull(llvm.PointerType(c.getLLVMRuntimeType("interfaceMethodInfo"), 0))
@@ -247,15 +246,16 @@ func (c *compilerContext) getTypeMethodSet(typ types.Type) llvm.Value {
 	for i := 0; i < ms.Len(); i++ {
 		method := ms.At(i)
 		signatureGlobal := c.getMethodSignature(method.Obj().(*types.Func))
-		f := c.ir.GetFunction(c.ir.Program.MethodValue(method))
-		if f.LLVMFn.IsNil() {
+		fn := c.program.MethodValue(method)
+		llvmFn := c.getFunction(fn)
+		if llvmFn.IsNil() {
 			// compiler error, so panic
-			panic("cannot find function: " + f.LinkName())
+			panic("cannot find function: " + c.getFunctionInfo(fn).linkName)
 		}
-		fn := c.getInterfaceInvokeWrapper(f)
+		wrapper := c.getInterfaceInvokeWrapper(fn, llvmFn)
 		methodInfo := llvm.ConstNamedStruct(interfaceMethodInfoType, []llvm.Value{
 			signatureGlobal,
-			llvm.ConstPtrToInt(fn, c.uintptrType),
+			llvm.ConstPtrToInt(wrapper, c.uintptrType),
 		})
 		methods[i] = methodInfo
 	}
@@ -303,7 +303,7 @@ func (c *compilerContext) getInterfaceMethodSet(typ types.Type) llvm.Value {
 // external *i8 indicating the indicating the signature of this method. It is
 // used during the interface lowering pass.
 func (c *compilerContext) getMethodSignature(method *types.Func) llvm.Value {
-	signature := ir.MethodSignature(method)
+	signature := methodSignature(method)
 	signatureGlobal := c.mod.NamedGlobal("func " + signature)
 	if signatureGlobal.IsNil() {
 		signatureGlobal = llvm.AddGlobal(c.mod, c.ctx.Int8Type(), "func "+signature)
@@ -357,8 +357,8 @@ func (b *builder) createTypeAssert(expr *ssa.TypeAssert) llvm.Value {
 	// value.
 
 	prevBlock := b.GetInsertBlock()
-	okBlock := b.ctx.AddBasicBlock(b.fn.LLVMFn, "typeassert.ok")
-	nextBlock := b.ctx.AddBasicBlock(b.fn.LLVMFn, "typeassert.next")
+	okBlock := b.ctx.AddBasicBlock(b.llvmFn, "typeassert.ok")
+	nextBlock := b.ctx.AddBasicBlock(b.llvmFn, "typeassert.next")
 	b.blockExits[b.currentBlock] = nextBlock // adjust outgoing block for phi nodes
 	b.CreateCondBr(commaOk, okBlock, nextBlock)
 
@@ -436,8 +436,8 @@ func (b *builder) getInvokeCall(instr *ssa.CallCommon) (llvm.Value, []llvm.Value
 // value, dereferences or unpacks it if necessary, and calls the real method.
 // If the method to wrap has a pointer receiver, no wrapping is necessary and
 // the function is returned directly.
-func (c *compilerContext) getInterfaceInvokeWrapper(f *ir.Function) llvm.Value {
-	wrapperName := f.LinkName() + "$invoke"
+func (c *compilerContext) getInterfaceInvokeWrapper(fn *ssa.Function, llvmFn llvm.Value) llvm.Value {
+	wrapperName := llvmFn.Name() + "$invoke"
 	wrapper := c.mod.NamedFunction(wrapperName)
 	if !wrapper.IsNil() {
 		// Wrapper already created. Return it directly.
@@ -445,7 +445,7 @@ func (c *compilerContext) getInterfaceInvokeWrapper(f *ir.Function) llvm.Value {
 	}
 
 	// Get the expanded receiver type.
-	receiverType := c.getLLVMType(f.Params[0].Type())
+	receiverType := c.getLLVMType(fn.Params[0].Type())
 	var expandedReceiverType []llvm.Type
 	for _, info := range expandFormalParamType(receiverType, "", nil) {
 		expandedReceiverType = append(expandedReceiverType, info.llvmType)
@@ -457,11 +457,11 @@ func (c *compilerContext) getInterfaceInvokeWrapper(f *ir.Function) llvm.Value {
 		// Casting a function signature to a different signature and calling it
 		// with a receiver pointer bitcasted to *i8 (as done in calls on an
 		// interface) is hopefully a safe (defined) operation.
-		return f.LLVMFn
+		return llvmFn
 	}
 
 	// create wrapper function
-	fnType := f.LLVMFn.Type().ElementType()
+	fnType := llvmFn.Type().ElementType()
 	paramTypes := append([]llvm.Type{c.i8ptrType}, fnType.ParamTypes()[len(expandedReceiverType):]...)
 	wrapFnType := llvm.FunctionType(fnType.ReturnType(), paramTypes, false)
 	wrapper = llvm.AddFunction(c.mod, wrapperName, wrapFnType)
@@ -479,8 +479,8 @@ func (c *compilerContext) getInterfaceInvokeWrapper(f *ir.Function) llvm.Value {
 
 	// add debug info if needed
 	if c.Debug() {
-		pos := c.ir.Program.Fset.Position(f.Pos())
-		difunc := c.attachDebugInfoRaw(f, wrapper, "$invoke", pos.Filename, pos.Line)
+		pos := c.program.Fset.Position(fn.Pos())
+		difunc := c.attachDebugInfoRaw(fn, wrapper, "$invoke", pos.Filename, pos.Line)
 		b.SetCurrentDebugLocation(uint(pos.Line), uint(pos.Column), difunc, llvm.Metadata{})
 	}
 
@@ -490,13 +490,60 @@ func (c *compilerContext) getInterfaceInvokeWrapper(f *ir.Function) llvm.Value {
 
 	receiverValue := b.emitPointerUnpack(wrapper.Param(0), []llvm.Type{receiverType})[0]
 	params := append(b.expandFormalParam(receiverValue), wrapper.Params()[1:]...)
-	if f.LLVMFn.Type().ElementType().ReturnType().TypeKind() == llvm.VoidTypeKind {
-		b.CreateCall(f.LLVMFn, params, "")
+	if llvmFn.Type().ElementType().ReturnType().TypeKind() == llvm.VoidTypeKind {
+		b.CreateCall(llvmFn, params, "")
 		b.CreateRetVoid()
 	} else {
-		ret := b.CreateCall(f.LLVMFn, params, "ret")
+		ret := b.CreateCall(llvmFn, params, "ret")
 		b.CreateRet(ret)
 	}
 
 	return wrapper
 }
+
+// methodSignature creates a readable version of a method signature (including
+// the function name, excluding the receiver name). This string is used
+// internally to match interfaces and to call the correct method on an
+// interface. Examples:
+//
+//     String() string
+//     Read([]byte) (int, error)
+func methodSignature(method *types.Func) string {
+	return method.Name() + signature(method.Type().(*types.Signature))
+}
+
+// Make a readable version of a function (pointer) signature.
+// Examples:
+//
+//     () string
+//     (string, int) (int, error)
+func signature(sig *types.Signature) string {
+	s := ""
+	if sig.Params().Len() == 0 {
+		s += "()"
+	} else {
+		s += "("
+		for i := 0; i < sig.Params().Len(); i++ {
+			if i > 0 {
+				s += ", "
+			}
+			s += sig.Params().At(i).Type().String()
+		}
+		s += ")"
+	}
+	if sig.Results().Len() == 0 {
+		// keep as-is
+	} else if sig.Results().Len() == 1 {
+		s += " " + sig.Results().At(0).Type().String()
+	} else {
+		s += " ("
+		for i := 0; i < sig.Results().Len(); i++ {
+			if i > 0 {
+				s += ", "
+			}
+			s += sig.Results().At(i).Type().String()
+		}
+		s += ")"
+	}
+	return s
+}
diff --git a/compiler/interrupt.go b/compiler/interrupt.go
index e4e31c0807..82585d56b7 100644
--- a/compiler/interrupt.go
+++ b/compiler/interrupt.go
@@ -39,7 +39,7 @@ func (b *builder) createInterruptGlobal(instr *ssa.CallCommon) (llvm.Value, erro
 
 	// Create a new global of type runtime/interrupt.handle. Globals of this
 	// type are lowered in the interrupt lowering pass.
-	globalType := b.ir.Program.ImportedPackage("runtime/interrupt").Type("handle").Type()
+	globalType := b.program.ImportedPackage("runtime/interrupt").Type("handle").Type()
 	globalLLVMType := b.getLLVMType(globalType)
 	globalName := "runtime/interrupt.$interrupt" + strconv.FormatInt(id.Int64(), 10)
 	if global := b.mod.NamedGlobal(globalName); !global.IsNil() {
@@ -56,7 +56,7 @@ func (b *builder) createInterruptGlobal(instr *ssa.CallCommon) (llvm.Value, erro
 
 	// Add debug info to the interrupt global.
 	if b.Debug() {
-		pos := b.ir.Program.Fset.Position(instr.Pos())
+		pos := b.program.Fset.Position(instr.Pos())
 		diglobal := b.dibuilder.CreateGlobalVariableExpression(b.getDIFile(pos.Filename), llvm.DIGlobalVariableExpression{
 			Name:        "interrupt" + strconv.FormatInt(id.Int64(), 10),
 			LinkageName: globalName,
diff --git a/compiler/passes.go b/compiler/passes.go
new file mode 100644
index 0000000000..092f5f0b50
--- /dev/null
+++ b/compiler/passes.go
@@ -0,0 +1,164 @@
+package compiler
+
+// This file implements a simple reachability analysis, to reduce compile time.
+// This DCE pass used to be necessary for improving other passes but now it
+// isn't necessary anymore.
+
+import (
+	"errors"
+	"go/types"
+	"sort"
+
+	"github.com/tinygo-org/tinygo/loader"
+	"golang.org/x/tools/go/ssa"
+)
+
+type dceState struct {
+	*compilerContext
+	functions   []*dceFunction
+	functionMap map[*ssa.Function]*dceFunction
+}
+
+type dceFunction struct {
+	*ssa.Function
+	functionInfo
+	flag bool // used by dead code elimination
+}
+
+func (p *dceState) addFunction(ssaFn *ssa.Function) {
+	if _, ok := p.functionMap[ssaFn]; ok {
+		return
+	}
+	f := &dceFunction{Function: ssaFn}
+	f.functionInfo = p.getFunctionInfo(ssaFn)
+	p.functions = append(p.functions, f)
+	p.functionMap[ssaFn] = f
+
+	for _, anon := range ssaFn.AnonFuncs {
+		p.addFunction(anon)
+	}
+}
+
+// simpleDCE returns a list of alive functions in the program. Compiling only
+// these functions makes the compiler faster.
+//
+// This functionality will likely be replaced in the future with build caching.
+func (c *compilerContext) simpleDCE(lprogram *loader.Program) ([]*ssa.Function, error) {
+	mainPkg := c.program.Package(lprogram.MainPkg().Pkg)
+	if mainPkg == nil {
+		panic("could not find main package")
+	}
+	p := &dceState{
+		compilerContext: c,
+		functionMap:     make(map[*ssa.Function]*dceFunction),
+	}
+
+	for _, pkg := range lprogram.Sorted() {
+		pkg := c.program.Package(pkg.Pkg)
+		memberNames := make([]string, 0)
+		for name := range pkg.Members {
+			memberNames = append(memberNames, name)
+		}
+		sort.Strings(memberNames)
+
+		for _, name := range memberNames {
+			member := pkg.Members[name]
+			switch member := member.(type) {
+			case *ssa.Function:
+				p.addFunction(member)
+			case *ssa.Type:
+				methods := getAllMethods(pkg.Prog, member.Type())
+				if !types.IsInterface(member.Type()) {
+					// named type
+					for _, method := range methods {
+						p.addFunction(pkg.Prog.MethodValue(method))
+					}
+				}
+			case *ssa.Global:
+				// Ignore. Globals are not handled here.
+			case *ssa.NamedConst:
+				// Ignore: these are already resolved.
+			default:
+				panic("unknown member type: " + member.String())
+			}
+		}
+	}
+
+	// Initial set of live functions. Include main.main, *.init and runtime.*
+	// functions.
+	main, ok := mainPkg.Members["main"].(*ssa.Function)
+	if !ok {
+		if mainPkg.Members["main"] == nil {
+			return nil, errors.New("function main is undeclared in the main package")
+		} else {
+			return nil, errors.New("cannot declare main - must be func")
+		}
+	}
+	runtimePkg := c.program.ImportedPackage("runtime")
+	mathPkg := c.program.ImportedPackage("math")
+	taskPkg := c.program.ImportedPackage("internal/task")
+	p.functionMap[main].flag = true
+	worklist := []*ssa.Function{main}
+	for _, f := range p.functions {
+		if f.exported || f.Synthetic == "package initializer" || f.Pkg == runtimePkg || f.Pkg == taskPkg || (f.Pkg == mathPkg && f.Pkg != nil) {
+			if f.flag {
+				continue
+			}
+			f.flag = true
+			worklist = append(worklist, f.Function)
+		}
+	}
+
+	// Mark all called functions recursively.
+	for len(worklist) != 0 {
+		f := worklist[len(worklist)-1]
+		worklist = worklist[:len(worklist)-1]
+		for _, block := range f.Blocks {
+			for _, instr := range block.Instrs {
+				if instr, ok := instr.(*ssa.MakeInterface); ok {
+					for _, sel := range getAllMethods(c.program, instr.X.Type()) {
+						fn := c.program.MethodValue(sel)
+						callee := p.functionMap[fn]
+						if callee == nil {
+							// TODO: why is this necessary?
+							p.addFunction(fn)
+							callee = p.functionMap[fn]
+						}
+						if !callee.flag {
+							callee.flag = true
+							worklist = append(worklist, callee.Function)
+						}
+					}
+				}
+				for _, operand := range instr.Operands(nil) {
+					if operand == nil || *operand == nil {
+						continue
+					}
+					switch operand := (*operand).(type) {
+					case *ssa.Function:
+						f := p.functionMap[operand]
+						if f == nil {
+							// FIXME HACK: this function should have been
+							// discovered already. It is not for bound methods.
+							p.addFunction(operand)
+							f = p.functionMap[operand]
+						}
+						if !f.flag {
+							f.flag = true
+							worklist = append(worklist, operand)
+						}
+					}
+				}
+			}
+		}
+	}
+
+	// Return all live functions.
+	liveFunctions := []*ssa.Function{}
+	for _, f := range p.functions {
+		if f.flag {
+			liveFunctions = append(liveFunctions, f.Function)
+		}
+	}
+	return liveFunctions, nil
+}
diff --git a/compiler/symbol.go b/compiler/symbol.go
index ec7cd34092..89525f4933 100644
--- a/compiler/symbol.go
+++ b/compiler/symbol.go
@@ -15,6 +15,197 @@ import (
 	"tinygo.org/x/go-llvm"
 )
 
+// functionInfo contains some information about a function or method. In
+// particular, it contains information obtained from pragmas.
+//
+// The linkName value contains a valid link name, even if //go:linkname is not
+// present.
+type functionInfo struct {
+	module   string     // go:wasm-module
+	linkName string     // go:linkname, go:export
+	exported bool       // go:export, CGo
+	nobounds bool       // go:nobounds
+	inline   inlineType // go:inline
+}
+
+type inlineType int
+
+// How much to inline.
+const (
+	// Default behavior. The compiler decides for itself whether any given
+	// function will be inlined. Whether any function is inlined depends on the
+	// optimization level.
+	inlineDefault inlineType = iota
+
+	// Inline hint, just like the C inline keyword (signalled using
+	// //go:inline). The compiler will be more likely to inline this function,
+	// but it is not a guarantee.
+	inlineHint
+
+	// Don't inline, just like the GCC noinline attribute. Signalled using
+	// //go:noinline.
+	inlineNone
+)
+
+// getFunction returns the LLVM function for the given *ssa.Function, creating
+// it if needed. It can later be filled with compilerContext.createFunction().
+func (c *compilerContext) getFunction(fn *ssa.Function) llvm.Value {
+	info := c.getFunctionInfo(fn)
+	llvmFn := c.mod.NamedFunction(info.linkName)
+	if !llvmFn.IsNil() {
+		return llvmFn
+	}
+
+	var retType llvm.Type
+	if fn.Signature.Results() == nil {
+		retType = c.ctx.VoidType()
+	} else if fn.Signature.Results().Len() == 1 {
+		retType = c.getLLVMType(fn.Signature.Results().At(0).Type())
+	} else {
+		results := make([]llvm.Type, 0, fn.Signature.Results().Len())
+		for i := 0; i < fn.Signature.Results().Len(); i++ {
+			results = append(results, c.getLLVMType(fn.Signature.Results().At(i).Type()))
+		}
+		retType = c.ctx.StructType(results, false)
+	}
+
+	var paramInfos []paramInfo
+	for _, param := range fn.Params {
+		paramType := c.getLLVMType(param.Type())
+		paramFragmentInfos := expandFormalParamType(paramType, param.Name(), param.Type())
+		paramInfos = append(paramInfos, paramFragmentInfos...)
+	}
+
+	// Add an extra parameter as the function context. This context is used in
+	// closures and bound methods, but should be optimized away when not used.
+	if !info.exported {
+		paramInfos = append(paramInfos, paramInfo{llvmType: c.i8ptrType, name: "context", flags: 0})
+		paramInfos = append(paramInfos, paramInfo{llvmType: c.i8ptrType, name: "parentHandle", flags: 0})
+	}
+
+	var paramTypes []llvm.Type
+	for _, info := range paramInfos {
+		paramTypes = append(paramTypes, info.llvmType)
+	}
+
+	fnType := llvm.FunctionType(retType, paramTypes, false)
+	llvmFn = llvm.AddFunction(c.mod, info.linkName, fnType)
+
+	dereferenceableOrNullKind := llvm.AttributeKindID("dereferenceable_or_null")
+	for i, info := range paramInfos {
+		if info.flags&paramIsDeferenceableOrNull == 0 {
+			continue
+		}
+		if info.llvmType.TypeKind() == llvm.PointerTypeKind {
+			el := info.llvmType.ElementType()
+			size := c.targetData.TypeAllocSize(el)
+			if size == 0 {
+				// dereferenceable_or_null(0) appears to be illegal in LLVM.
+				continue
+			}
+			dereferenceableOrNull := c.ctx.CreateEnumAttribute(dereferenceableOrNullKind, size)
+			llvmFn.AddAttributeAtIndex(i+1, dereferenceableOrNull)
+		}
+	}
+
+	// External/exported functions may not retain pointer values.
+	// https://golang.org/cmd/cgo/#hdr-Passing_pointers
+	if info.exported {
+		// Set the wasm-import-module attribute if the function's module is set.
+		if info.module != "" {
+			wasmImportModuleAttr := c.ctx.CreateStringAttribute("wasm-import-module", info.module)
+			llvmFn.AddFunctionAttr(wasmImportModuleAttr)
+		}
+		nocaptureKind := llvm.AttributeKindID("nocapture")
+		nocapture := c.ctx.CreateEnumAttribute(nocaptureKind, 0)
+		for i, typ := range paramTypes {
+			if typ.TypeKind() == llvm.PointerTypeKind {
+				llvmFn.AddAttributeAtIndex(i+1, nocapture)
+			}
+		}
+	}
+
+	return llvmFn
+}
+
+// getFunctionInfo returns information about a function that is not directly
+// present in *ssa.Function, such as the link name and whether it should be
+// exported.
+func (c *compilerContext) getFunctionInfo(f *ssa.Function) functionInfo {
+	info := functionInfo{}
+	if strings.HasPrefix(f.Name(), "C.") {
+		// Created by CGo: such a name cannot be created by regular C code.
+		info.linkName = f.Name()[2:]
+		info.exported = true
+	} else {
+		// Pick the default linkName.
+		info.linkName = f.RelString(nil)
+		// Check for //go: pragmas, which may change the link name (among
+		// others).
+		info.parsePragmas(f)
+	}
+	return info
+}
+
+// parsePragmas is used by getFunctionInfo to parse function pragmas such as
+// //export or //go:noinline.
+func (info *functionInfo) parsePragmas(f *ssa.Function) {
+	if f.Syntax() == nil {
+		return
+	}
+	if decl, ok := f.Syntax().(*ast.FuncDecl); ok && decl.Doc != nil {
+		for _, comment := range decl.Doc.List {
+			text := comment.Text
+			if strings.HasPrefix(text, "//export ") {
+				// Rewrite '//export' to '//go:export' for compatibility with
+				// gc.
+				text = "//go:" + text[2:]
+			}
+			if !strings.HasPrefix(text, "//go:") {
+				continue
+			}
+			parts := strings.Fields(text)
+			switch parts[0] {
+			case "//go:export":
+				if len(parts) != 2 {
+					continue
+				}
+				info.linkName = parts[1]
+				info.exported = true
+			case "//go:wasm-module":
+				// Alternative comment for setting the import module.
+				if len(parts) != 2 {
+					continue
+				}
+				info.module = parts[1]
+			case "//go:inline":
+				info.inline = inlineHint
+			case "//go:noinline":
+				info.inline = inlineNone
+			case "//go:linkname":
+				if len(parts) != 3 || parts[1] != f.Name() {
+					continue
+				}
+				// Only enable go:linkname when the package imports "unsafe".
+				// This is a slightly looser requirement than what gc uses: gc
+				// requires the file to import "unsafe", not the package as a
+				// whole.
+				if hasUnsafeImport(f.Pkg.Pkg) {
+					info.linkName = parts[2]
+				}
+			case "//go:nobounds":
+				// Skip bounds checking in this function. Useful for some
+				// runtime functions.
+				// This is somewhat dangerous and thus only imported in packages
+				// that import unsafe.
+				if hasUnsafeImport(f.Pkg.Pkg) {
+					info.nobounds = true
+				}
+			}
+		}
+	}
+}
+
 // globalInfo contains some information about a specific global. By default,
 // linkName is equal to .RelString(nil) on a global and extern is false, but for
 // some symbols this is different (due to //go:extern for example).
@@ -86,7 +277,7 @@ func (c *compilerContext) getGlobal(g *ssa.Global) llvm.Value {
 			// Add debug info.
 			// TODO: this should be done for every global in the program, not just
 			// the ones that are referenced from some code.
-			pos := c.ir.Program.Fset.Position(g.Pos())
+			pos := c.program.Fset.Position(g.Pos())
 			diglobal := c.dibuilder.CreateGlobalVariableExpression(c.difiles[pos.Filename], llvm.DIGlobalVariableExpression{
 				Name:        g.RelString(nil),
 				LinkageName: info.linkName,
@@ -145,3 +336,23 @@ func (info *globalInfo) parsePragmas(doc *ast.CommentGroup) {
 		}
 	}
 }
+
+// Get all methods of a type.
+func getAllMethods(prog *ssa.Program, typ types.Type) []*types.Selection {
+	ms := prog.MethodSets.MethodSet(typ)
+	methods := make([]*types.Selection, ms.Len())
+	for i := 0; i < ms.Len(); i++ {
+		methods[i] = ms.At(i)
+	}
+	return methods
+}
+
+// Return true if this package imports "unsafe", false otherwise.
+func hasUnsafeImport(pkg *types.Package) bool {
+	for _, imp := range pkg.Imports() {
+		if imp == types.Unsafe {
+			return true
+		}
+	}
+	return false
+}
diff --git a/ir/ir.go b/ir/ir.go
deleted file mode 100644
index abbb403c32..0000000000
--- a/ir/ir.go
+++ /dev/null
@@ -1,271 +0,0 @@
-package ir
-
-import (
-	"go/ast"
-	"go/types"
-	"sort"
-	"strings"
-
-	"github.com/tinygo-org/tinygo/loader"
-	"golang.org/x/tools/go/ssa"
-	"tinygo.org/x/go-llvm"
-)
-
-// This file provides a wrapper around go/ssa values and adds extra
-// functionality to them.
-
-// View on all functions, types, and globals in a program, with analysis
-// results.
-type Program struct {
-	Program       *ssa.Program
-	LoaderProgram *loader.Program
-	mainPkg       *ssa.Package
-	Functions     []*Function
-	functionMap   map[*ssa.Function]*Function
-}
-
-// Function or method.
-type Function struct {
-	*ssa.Function
-	LLVMFn   llvm.Value
-	module   string     // go:wasm-module
-	linkName string     // go:linkname, go:export
-	exported bool       // go:export
-	nobounds bool       // go:nobounds
-	flag     bool       // used by dead code elimination
-	inline   InlineType // go:inline
-}
-
-// Interface type that is at some point used in a type assert (to check whether
-// it implements another interface).
-type Interface struct {
-	Num  int
-	Type *types.Interface
-}
-
-type InlineType int
-
-// How much to inline.
-const (
-	// Default behavior. The compiler decides for itself whether any given
-	// function will be inlined. Whether any function is inlined depends on the
-	// optimization level.
-	InlineDefault InlineType = iota
-
-	// Inline hint, just like the C inline keyword (signalled using
-	// //go:inline). The compiler will be more likely to inline this function,
-	// but it is not a guarantee.
-	InlineHint
-
-	// Don't inline, just like the GCC noinline attribute. Signalled using
-	// //go:noinline.
-	InlineNone
-)
-
-// Create and initialize a new *Program from a *ssa.Program.
-func NewProgram(lprogram *loader.Program) *Program {
-	program := lprogram.LoadSSA()
-	program.Build()
-
-	mainPkg := program.Package(lprogram.MainPkg().Pkg)
-	if mainPkg == nil {
-		panic("could not find main package")
-	}
-	p := &Program{
-		Program:       program,
-		LoaderProgram: lprogram,
-		mainPkg:       mainPkg,
-		functionMap:   make(map[*ssa.Function]*Function),
-	}
-
-	for _, pkg := range lprogram.Sorted() {
-		p.AddPackage(program.Package(pkg.Pkg))
-	}
-
-	return p
-}
-
-// Add a package to this Program. All packages need to be added first before any
-// analysis is done for correct results.
-func (p *Program) AddPackage(pkg *ssa.Package) {
-	memberNames := make([]string, 0)
-	for name := range pkg.Members {
-		memberNames = append(memberNames, name)
-	}
-	sort.Strings(memberNames)
-
-	for _, name := range memberNames {
-		member := pkg.Members[name]
-		switch member := member.(type) {
-		case *ssa.Function:
-			p.addFunction(member)
-		case *ssa.Type:
-			methods := getAllMethods(pkg.Prog, member.Type())
-			if !types.IsInterface(member.Type()) {
-				// named type
-				for _, method := range methods {
-					p.addFunction(pkg.Prog.MethodValue(method))
-				}
-			}
-		case *ssa.Global:
-			// Ignore. Globals are not handled here.
-		case *ssa.NamedConst:
-			// Ignore: these are already resolved.
-		default:
-			panic("unknown member type: " + member.String())
-		}
-	}
-}
-
-func (p *Program) addFunction(ssaFn *ssa.Function) {
-	if _, ok := p.functionMap[ssaFn]; ok {
-		return
-	}
-	f := &Function{Function: ssaFn}
-	f.parsePragmas()
-	p.Functions = append(p.Functions, f)
-	p.functionMap[ssaFn] = f
-
-	for _, anon := range ssaFn.AnonFuncs {
-		p.addFunction(anon)
-	}
-}
-
-// Return true if this package imports "unsafe", false otherwise.
-func hasUnsafeImport(pkg *types.Package) bool {
-	for _, imp := range pkg.Imports() {
-		if imp == types.Unsafe {
-			return true
-		}
-	}
-	return false
-}
-
-func (p *Program) GetFunction(ssaFn *ssa.Function) *Function {
-	return p.functionMap[ssaFn]
-}
-
-func (p *Program) MainPkg() *ssa.Package {
-	return p.mainPkg
-}
-
-// Parse compiler directives in the preceding comments.
-func (f *Function) parsePragmas() {
-	if f.Syntax() == nil {
-		return
-	}
-	if decl, ok := f.Syntax().(*ast.FuncDecl); ok && decl.Doc != nil {
-		for _, comment := range decl.Doc.List {
-			text := comment.Text
-			if strings.HasPrefix(text, "//export ") {
-				// Rewrite '//export' to '//go:export' for compatibility with
-				// gc.
-				text = "//go:" + text[2:]
-			}
-			if !strings.HasPrefix(text, "//go:") {
-				continue
-			}
-			parts := strings.Fields(text)
-			switch parts[0] {
-			case "//go:export":
-				if len(parts) != 2 {
-					continue
-				}
-				f.linkName = parts[1]
-				f.exported = true
-			case "//go:wasm-module":
-				// Alternative comment for setting the import module.
-				if len(parts) != 2 {
-					continue
-				}
-				f.module = parts[1]
-			case "//go:inline":
-				f.inline = InlineHint
-			case "//go:noinline":
-				f.inline = InlineNone
-			case "//go:linkname":
-				if len(parts) != 3 || parts[1] != f.Name() {
-					continue
-				}
-				// Only enable go:linkname when the package imports "unsafe".
-				// This is a slightly looser requirement than what gc uses: gc
-				// requires the file to import "unsafe", not the package as a
-				// whole.
-				if hasUnsafeImport(f.Pkg.Pkg) {
-					f.linkName = parts[2]
-				}
-			case "//go:nobounds":
-				// Skip bounds checking in this function. Useful for some
-				// runtime functions.
-				// This is somewhat dangerous and thus only imported in packages
-				// that import unsafe.
-				if hasUnsafeImport(f.Pkg.Pkg) {
-					f.nobounds = true
-				}
-			}
-		}
-	}
-}
-
-func (f *Function) IsNoBounds() bool {
-	return f.nobounds
-}
-
-// Return true iff this function is externally visible.
-func (f *Function) IsExported() bool {
-	return f.exported || f.CName() != ""
-}
-
-// Return the inline directive of this function.
-func (f *Function) Inline() InlineType {
-	return f.inline
-}
-
-// Return the module name if not the default.
-func (f *Function) Module() string {
-	return f.module
-}
-
-// Return the link name for this function.
-func (f *Function) LinkName() string {
-	if f.linkName != "" {
-		return f.linkName
-	}
-	if f.Signature.Recv() != nil {
-		// Method on a defined type (which may be a pointer).
-		return f.RelString(nil)
-	} else {
-		// Bare function.
-		if name := f.CName(); name != "" {
-			// Name CGo functions directly.
-			return name
-		} else {
-			return f.RelString(nil)
-		}
-	}
-}
-
-// Return the name of the C function if this is a CGo wrapper. Otherwise, return
-// a zero-length string.
-func (f *Function) CName() string {
-	name := f.Name()
-	if strings.HasPrefix(name, "_Cfunc_") {
-		// emitted by `go tool cgo`
-		return name[len("_Cfunc_"):]
-	}
-	if strings.HasPrefix(name, "C.") {
-		// created by ../loader/cgo.go
-		return name[2:]
-	}
-	return ""
-}
-
-// Get all methods of a type.
-func getAllMethods(prog *ssa.Program, typ types.Type) []*types.Selection {
-	ms := prog.MethodSets.MethodSet(typ)
-	methods := make([]*types.Selection, ms.Len())
-	for i := 0; i < ms.Len(); i++ {
-		methods[i] = ms.At(i)
-	}
-	return methods
-}
diff --git a/ir/passes.go b/ir/passes.go
deleted file mode 100644
index ea5ecccbe0..0000000000
--- a/ir/passes.go
+++ /dev/null
@@ -1,149 +0,0 @@
-package ir
-
-import (
-	"errors"
-	"go/types"
-
-	"golang.org/x/tools/go/ssa"
-)
-
-// This file implements several optimization passes (analysis + transform) to
-// optimize code in SSA form before it is compiled to LLVM IR. It is based on
-// the IR defined in ir.go.
-
-// Make a readable version of a method signature (including the function name,
-// excluding the receiver name). This string is used internally to match
-// interfaces and to call the correct method on an interface. Examples:
-//
-//     String() string
-//     Read([]byte) (int, error)
-func MethodSignature(method *types.Func) string {
-	return method.Name() + signature(method.Type().(*types.Signature))
-}
-
-// Make a readable version of a function (pointer) signature.
-// Examples:
-//
-//     () string
-//     (string, int) (int, error)
-func signature(sig *types.Signature) string {
-	s := ""
-	if sig.Params().Len() == 0 {
-		s += "()"
-	} else {
-		s += "("
-		for i := 0; i < sig.Params().Len(); i++ {
-			if i > 0 {
-				s += ", "
-			}
-			s += sig.Params().At(i).Type().String()
-		}
-		s += ")"
-	}
-	if sig.Results().Len() == 0 {
-		// keep as-is
-	} else if sig.Results().Len() == 1 {
-		s += " " + sig.Results().At(0).Type().String()
-	} else {
-		s += " ("
-		for i := 0; i < sig.Results().Len(); i++ {
-			if i > 0 {
-				s += ", "
-			}
-			s += sig.Results().At(i).Type().String()
-		}
-		s += ")"
-	}
-	return s
-}
-
-// Simple pass that removes dead code. This pass makes later analysis passes
-// more useful.
-func (p *Program) SimpleDCE() error {
-	// Unmark all functions.
-	for _, f := range p.Functions {
-		f.flag = false
-	}
-
-	// Initial set of live functions. Include main.main, *.init and runtime.*
-	// functions.
-	main, ok := p.mainPkg.Members["main"].(*ssa.Function)
-	if !ok {
-		if p.mainPkg.Members["main"] == nil {
-			return errors.New("function main is undeclared in the main package")
-		} else {
-			return errors.New("cannot declare main - must be func")
-		}
-	}
-	runtimePkg := p.Program.ImportedPackage("runtime")
-	mathPkg := p.Program.ImportedPackage("math")
-	taskPkg := p.Program.ImportedPackage("internal/task")
-	p.GetFunction(main).flag = true
-	worklist := []*ssa.Function{main}
-	for _, f := range p.Functions {
-		if f.exported || f.Synthetic == "package initializer" || f.Pkg == runtimePkg || f.Pkg == taskPkg || (f.Pkg == mathPkg && f.Pkg != nil) {
-			if f.flag {
-				continue
-			}
-			f.flag = true
-			worklist = append(worklist, f.Function)
-		}
-	}
-
-	// Mark all called functions recursively.
-	for len(worklist) != 0 {
-		f := worklist[len(worklist)-1]
-		worklist = worklist[:len(worklist)-1]
-		for _, block := range f.Blocks {
-			for _, instr := range block.Instrs {
-				if instr, ok := instr.(*ssa.MakeInterface); ok {
-					for _, sel := range getAllMethods(p.Program, instr.X.Type()) {
-						fn := p.Program.MethodValue(sel)
-						callee := p.GetFunction(fn)
-						if callee == nil {
-							// TODO: why is this necessary?
-							p.addFunction(fn)
-							callee = p.GetFunction(fn)
-						}
-						if !callee.flag {
-							callee.flag = true
-							worklist = append(worklist, callee.Function)
-						}
-					}
-				}
-				for _, operand := range instr.Operands(nil) {
-					if operand == nil || *operand == nil {
-						continue
-					}
-					switch operand := (*operand).(type) {
-					case *ssa.Function:
-						f := p.GetFunction(operand)
-						if f == nil {
-							// FIXME HACK: this function should have been
-							// discovered already. It is not for bound methods.
-							p.addFunction(operand)
-							f = p.GetFunction(operand)
-						}
-						if !f.flag {
-							f.flag = true
-							worklist = append(worklist, operand)
-						}
-					}
-				}
-			}
-		}
-	}
-
-	// Remove unmarked functions.
-	livefunctions := []*Function{}
-	for _, f := range p.Functions {
-		if f.flag {
-			livefunctions = append(livefunctions, f)
-		} else {
-			delete(p.functionMap, f.Function)
-		}
-	}
-	p.Functions = livefunctions
-
-	return nil
-}