cmd/compile: fix typos

Change-Id: I88a3e69e232bf94296fe97621c5d395fc1296bbb
GitHub-Last-Rev: f1cc29dc28
GitHub-Pull-Request: golang/go#47482
Reviewed-on: https://go-review.googlesource.com/c/go/+/338751
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Trust: Josh Bleecher Snyder <josharian@gmail.com>

src/cmd/compile/internal/escape/graph.go

@@ -117,7 +117,7 @@ func (l *location) isName(c ir.Class) bool {
 	return l.n != nil && l.n.Op() == ir.ONAME && l.n.(*ir.Name).Class == c
 }
 
-// An hole represents a context for evaluation a Go
+// A hole represents a context for evaluation of a Go
 // expression. E.g., when evaluating p in "x = **p", we'd have a hole
 // with dst==x and derefs==2.
 type hole struct {

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

@@ -275,7 +275,7 @@ func (n *ConvExpr) SetOp(op Op) {
 	}
 }
 
-// An IndexExpr is an index expression X[Y].
+// An IndexExpr is an index expression X[Index].
 type IndexExpr struct {
 	miniExpr
 	X        Node

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

@@ -244,7 +244,7 @@ func NewGoDeferStmt(pos src.XPos, op Op, call Node) *GoDeferStmt {
 	return n
 }
 
-// A IfStmt is a return statement: if Init; Cond { Then } else { Else }.
+// An IfStmt is a return statement: if Init; Cond { Body } else { Else }.
 type IfStmt struct {
 	miniStmt
 	Cond   Node