Update Expr and Func with frequency

Author: Raj Barik

src/cmd/compile/internal/ir/expr.go

@@ -153,13 +153,20 @@ const (
 	CallUseStmt // results not used - call is a statement
 )
 
+// EdgeFrequency stores edge profile information for CallExpr where RawCount captures the raw sampled execution count and percent denotes the percentage of counts spent in this edge vs. the total edge samples collected.
+type EdgeFrequency struct {
+	RawCount int64
+	Percent  float64
+}
+
 // A CallExpr is a function call X(Args).
 type CallExpr struct {
 	miniExpr
 	origNode
 	X               Node
 	Args            Nodes
-	KeepAlive       []*Name // vars to be kept alive until call returns
+	KeepAlive       []*Name                 // vars to be kept alive until call returns
+	EdgeFreq        map[*Func]EdgeFrequency // Frequency of callee targets
 	IsDDD           bool
 	Use             CallUse
 	NoInline        bool

src/cmd/compile/internal/ir/func.go

@@ -11,6 +11,12 @@ import (
 	"cmd/internal/src"
 )
 
+// NodeFrequency stores profile data of an ir.Func where RawCount stores the number of samples and percent captures fraction samples spend in this function versus all samples collected.
+type NodeFrequency struct {
+	RawCount int64
+	Percent  float64
+}
+
 // A Func corresponds to a single function in a Go program
 // (and vice versa: each function is denoted by exactly one *Func).
 //
@@ -96,6 +102,8 @@ type Func struct {
 	LSym       *obj.LSym // Linker object in this function's native ABI (Func.ABI)
 
 	Inl *Inline
+	// Aggregated Weight of the function obtained from pprof profiles.
+	NodeFreq NodeFrequency
 
 	// Closgen tracks how many closures have been generated within
 	// this function. Used by closurename for creating unique