cmd/compile: make expandCalls preserve types of pointer stores

This is accomplished by checking for simple stores of pointer types
and leaving them alone.  The failure case was when a *mspan
(not in heap) stored type was replaced by unsafe.Pointer.

Updates #40724.

Change-Id: I529e1705bf58fb0e64e60d48fd550b3a407e57e7
Reviewed-on: https://go-review.googlesource.com/c/go/+/305672
Trust: David Chase <[email protected]>
Run-TryBot: David Chase <[email protected]>
TryBot-Result: Go Bot <[email protected]>
Reviewed-by: Cuong Manh Le <[email protected]>
Reviewed-by: Cherry Zhang <[email protected]>

Author: dr2chase

src/cmd/compile/internal/ssa/expand_calls.go

@@ -1114,6 +1114,9 @@ func expandCalls(f *Func) {
 		for _, v := range b.Values {
 			if v.Op == OpStore {
 				t := v.Aux.(*types.Type)
+				if t.IsPtrShaped() { // Everything already fits, and this ensures pointer type properties aren't discarded (e.g, notinheap)
+					continue
+				}
 				source := v.Args[1]
 				tSrc := source.Type
 				iAEATt := x.isAlreadyExpandedAggregateType(t)
@@ -1422,7 +1425,7 @@ func (x *expandState) newArgToMemOrRegs(baseArg, toReplace *Value, offset int64,
 	if x.debug {
 		x.indent(3)
 		defer x.indent(-3)
-		x.Printf("newArgToMemOrRegs(base=%s; toReplace=%s; t=%s; memOff=%d; regOff=%d)\n", baseArg.String(), toReplace.LongString(), t, offset, regOffset)
+		x.Printf("newArgToMemOrRegs(base=%s; toReplace=%s; t=%s; memOff=%d; regOff=%d)\n", baseArg.String(), toReplace.LongString(), t.String(), offset, regOffset)
 	}
 	key := selKey{baseArg, offset, t.Width, t}
 	w := x.commonArgs[key]

src/cmd/compile/internal/ssa/value.go

@@ -139,6 +139,9 @@ func (v *Value) AuxArm64BitField() arm64BitField {
 
 // long form print.  v# = opcode <type> [aux] args [: reg] (names)
 func (v *Value) LongString() string {
+	if v == nil {
+		return "<NIL VALUE>"
+	}
 	s := fmt.Sprintf("v%d = %s", v.ID, v.Op)
 	s += " <" + v.Type.String() + ">"
 	s += v.auxString()