cmd/compile: incorporate inlined function names into closure naming

In Go 1.17, cmd/compile gained the ability to inline calls to
functions that contain function literals (aka "closures"). This was
implemented by duplicating the function literal body and emitting a
second LSym, because in general it might be optimized better than the
original function literal.

However, the second LSym was named simply as any other function
literal appearing literally in the enclosing function would be named.
E.g., if f has a closure "f.funcX", and f is inlined into g, we would
create "g.funcY" (N.B., X and Y need not be the same.). Users then
have no idea this function originally came from f.

With this CL, the inlined call stack is incorporated into the clone
LSym's name: instead of "g.funcY", it's named "g.f.funcY".

In the future, it seems desirable to arrange for the clone's name to
appear exactly as the original name, so stack traces remain the same
as when -l or -d=inlfuncswithclosures are used. But it's unclear
whether the linker supports that today, or whether any downstream
tooling would be confused by this.

Updates #60324.

Change-Id: Ifad0ccef7e959e72005beeecdfffd872f63982f8
Reviewed-on: https://go-review.googlesource.com/c/go/+/497137
Reviewed-by: Michael Pratt <mpratt@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>

3 files changed, 37 insertions, 15 deletions

diff --git a/src/cmd/compile/internal/inline/inl.go b/src/cmd/compile/internal/inline/inl.go
index 96a6f3028a..c61d6d2234 100644
--- a/src/cmd/compile/internal/inline/inl.go
+++ b/src/cmd/compile/internal/inline/inl.go
@@ -1094,7 +1094,7 @@ func mkinlcall(n *ir.CallExpr, fn *ir.Func, bigCaller bool, inlCalls *[]*ir.Inli
 
 	typecheck.AssertFixedCall(n)
 
-	inlIndex := base.Ctxt.InlTree.Add(parent, n.Pos(), sym)
+	inlIndex := base.Ctxt.InlTree.Add(parent, n.Pos(), sym, ir.FuncName(fn))
 
 	closureInitLSym := func(n *ir.CallExpr, fn *ir.Func) {
 		// The linker needs FuncInfo metadata for all inlined
diff --git a/src/cmd/compile/internal/ir/func.go b/src/cmd/compile/internal/ir/func.go
index b36b1fa494..5c41893fc6 100644
--- a/src/cmd/compile/internal/ir/func.go
+++ b/src/cmd/compile/internal/ir/func.go
@@ -11,6 +11,7 @@ import (
 	"cmd/internal/objabi"
 	"cmd/internal/src"
 	"fmt"
+	"strings"
 )
 
 // A Func corresponds to a single function in a Go program
@@ -359,8 +360,8 @@ func IsTrivialClosure(clo *ClosureExpr) bool {
 // globClosgen is like Func.Closgen, but for the global scope.
 var globClosgen int32
 
-// closureName generates a new unique name for a closure within outerfn.
-func closureName(outerfn *Func) *types.Sym {
+// closureName generates a new unique name for a closure within outerfn at pos.
+func closureName(outerfn *Func, pos src.XPos) *types.Sym {
 	pkg := types.LocalPkg
 	outer := "glob."
 	prefix := "func"
@@ -382,6 +383,17 @@ func closureName(outerfn *Func) *types.Sym {
 		}
 	}
 
+	// If this closure was created due to inlining, then incorporate any
+	// inlined functions' names into the closure's linker symbol name
+	// too (#60324).
+	if inlIndex := base.Ctxt.InnermostPos(pos).Base().InliningIndex(); inlIndex >= 0 {
+		names := []string{outer}
+		base.Ctxt.InlTree.AllParents(inlIndex, func(call obj.InlinedCall) {
+			names = append(names, call.Name)
+		})
+		outer = strings.Join(names, ".")
+	}
+
 	*gen++
 	return pkg.Lookup(fmt.Sprintf("%s.%s%d", outer, prefix, *gen))
 }
@@ -418,7 +430,7 @@ func NameClosure(clo *ClosureExpr, outerfn *Func) {
 		base.FatalfAt(clo.Pos(), "closure already named: %v", name)
 	}
 
-	name.SetSym(closureName(outerfn))
+	name.SetSym(closureName(outerfn, clo.Pos()))
 	MarkFunc(name)
 }
 
diff --git a/src/cmd/internal/obj/inl.go b/src/cmd/internal/obj/inl.go
index 7a22eb1efd..6874471891 100644
--- a/src/cmd/internal/obj/inl.go
+++ b/src/cmd/internal/obj/inl.go
@@ -50,21 +50,37 @@ type InlinedCall struct {
 	Parent   int      // index of the parent in the InlTree or < 0 if outermost call
 	Pos      src.XPos // position of the inlined call
 	Func     *LSym    // function that was inlined
+	Name     string   // bare name of the function (w/o package prefix)
 	ParentPC int32    // PC of instruction just before inlined body. Only valid in local trees.
 }
 
 // Add adds a new call to the tree, returning its index.
-func (tree *InlTree) Add(parent int, pos src.XPos, func_ *LSym) int {
+func (tree *InlTree) Add(parent int, pos src.XPos, func_ *LSym, name string) int {
 	r := len(tree.nodes)
 	call := InlinedCall{
 		Parent: parent,
 		Pos:    pos,
 		Func:   func_,
+		Name:   name,
 	}
 	tree.nodes = append(tree.nodes, call)
 	return r
 }
 
+// AllParents invokes do on each InlinedCall in the inlining call
+// stack, from outermost to innermost.
+//
+// That is, if inlIndex corresponds to f inlining g inlining h,
+// AllParents invokes do with the call for inlining g into f, and then
+// inlining h into g.
+func (tree *InlTree) AllParents(inlIndex int, do func(InlinedCall)) {
+	if inlIndex >= 0 {
+		call := tree.nodes[inlIndex]
+		tree.AllParents(call.Parent, do)
+		do(call)
+	}
+}
+
 func (tree *InlTree) Parent(inlIndex int) int {
 	return tree.nodes[inlIndex].Parent
 }
@@ -113,16 +129,10 @@ func (ctxt *Link) InnermostPos(xpos src.XPos) src.Pos {
 // AllPos invokes do with the position in f, then the position in g, then the position in h.
 func (ctxt *Link) AllPos(xpos src.XPos, do func(src.Pos)) {
 	pos := ctxt.InnermostPos(xpos)
-	ctxt.forAllPos(pos.Base().InliningIndex(), do)
-	do(ctxt.PosTable.Pos(xpos))
-}
-
-func (ctxt *Link) forAllPos(ix int, do func(src.Pos)) {
-	if ix >= 0 {
-		call := ctxt.InlTree.nodes[ix]
-		ctxt.forAllPos(call.Parent, do)
-		do(ctxt.PosTable.Pos(call.Pos))
-	}
+	ctxt.InlTree.AllParents(pos.Base().InliningIndex(), func(call InlinedCall) {
+		do(ctxt.InnermostPos(call.Pos))
+	})
+	do(pos)
 }
 
 func dumpInlTree(ctxt *Link, tree InlTree) {