cmd/compile: fix race on initializing Sym symFunc flag

SSA lowering can create PFUNC ONAME nodes when compiling method calls.
Since we generally initialize the node's Sym to a func when we set its
class to PFUNC, we did this here, too. Unfortunately, since SSA
compilation is concurrent, this can cause a race if two function
compilations try to initialize the same symbol.

Luckily, we don't need to do this at all, since we're actually just
wrapping an ONAME node around an existing Sym that's already marked as
a function symbol.

Fixes the linux-amd64-racecompile builder, which was broken by CL
147158.

Updates #27539.

Change-Id: I8ddfce6e66a08ce53998c5bfa6f5a423c1ffc1eb
Reviewed-on: https://go-review.googlesource.com/c/149158
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>

diff --git a/src/cmd/compile/internal/gc/ssa.go b/src/cmd/compile/internal/gc/ssa.go
index 883cf7936d3b0511e4bc593f16278f0571c39979..9da45258f52686b9ffe4d6741fadf83ac1fc7a4a 100644 (file)
--- a/src/cmd/compile/internal/gc/ssa.go
+++ b/src/cmd/compile/internal/gc/ssa.go
@@ -3670,7 +3670,7 @@ func (s *state) call(n *Node, k callKind) *ssa.Value {
                n2 := newnamel(fn.Pos, fn.Sym)
                n2.Name.Curfn = s.curfn
                n2.SetClass(PFUNC)
-               n2.Sym.SetFunc(true)
+               // n2.Sym already existed, so it's already marked as a function.
                n2.Pos = fn.Pos
                n2.Type = types.Types[TUINT8] // dummy type for a static closure. Could use runtime.funcval if we had it.
                closure = s.expr(n2)