cmd/compile: inline functions evaluated in go and defer statements

The inlining pass previously bailed upon encountering a go or defer statement, so it would not inline functions e.g. used to provide arguments to the deferred function. This change preserves the behavior of not inlining the
deferred function itself, but it allows the inlining walk to proceed into its arguments.

Fixes #42194

Change-Id: I4e82029d8dcbe69019cc83ae63a4b29af45ec777
Reviewed-on: https://go-review.googlesource.com/c/go/+/264997
Run-TryBot: Cuong Manh Le <[email protected]>
TryBot-Result: Go Bot <[email protected]>
Reviewed-by: Cuong Manh Le <[email protected]>
Reviewed-by: Matthew Dempsky <[email protected]>
Trust: Cuong Manh Le <[email protected]>

Author: zephyrtronium

src/cmd/compile/internal/gc/inl.go

@@ -574,13 +574,11 @@ func inlnode(n *Node, maxCost int32, inlMap map[*Node]bool) *Node {
 	}
 
 	switch n.Op {
-	// inhibit inlining of their argument
 	case ODEFER, OGO:
 		switch n.Left.Op {
 		case OCALLFUNC, OCALLMETH:
 			n.Left.SetNoInline(true)
 		}
-		return n
 
 	// TODO do them here (or earlier),
 	// so escape analysis can avoid more heapmoves.

test/inline.go

@@ -246,3 +246,20 @@ func ii() { // ERROR "can inline ii"
 	f := getMeth(t1) // ERROR "inlining call to getMeth" "t1.meth does not escape"
 	_ = f(3)
 }
+
+// Issue #42194 - make sure that functions evaluated in
+// go and defer statements can be inlined.
+func gd1(int) {
+	defer gd1(gd2()) // ERROR "inlining call to gd2"
+	defer gd3()()    // ERROR "inlining call to gd3"
+	go gd1(gd2())    // ERROR "inlining call to gd2"
+	go gd3()()       // ERROR "inlining call to gd3"
+}
+
+func gd2() int { // ERROR "can inline gd2"
+	return 1
+}
+
+func gd3() func() { // ERROR "can inline gd3"
+	return ii
+}