From: Ian Lance Taylor Date: Sun, 20 Mar 2016 17:25:46 +0000 (-0700) Subject: cmd/compile: fix varexpr handling of ODOT X-Git-Tag: go1.7beta1~1203 X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=a9407b5797c0d4dcbed965462204cdc4e38bb621;p=gostls13.git cmd/compile: fix varexpr handling of ODOT For a long time varexpr has handled ODOT incorrectly: it has always returned false. Before https://golang.org/cl/20890 this has been because an ODOT had a Right field with an ONAME with no Class, for which varexpr returns false. CL 20890 preserved the behavior of varexpr for ODOT, so that the change would pass toolstash -cmp. This CL fixes varexpr so that ODOT can return true in some cases. This breaks toolstash -cmp. While the changed compiler allocates temporary variables in a different order, I have not been able to find any examples where the generated code is different, other than using different stack offsets and, in some cases, registers. It seems that other parts of the compiler will force the ODOT into a temporary anyhow. Still, this change is clearly correct, and is a minor compiler cleanup. Change-Id: I71506877aa3c13966bb03c281aa16271ee7fe80a Reviewed-on: https://go-review.googlesource.com/20907 Run-TryBot: Ian Lance Taylor Reviewed-by: David Crawshaw TryBot-Result: Gobot Gobot --- diff --git a/src/cmd/compile/internal/gc/walk.go b/src/cmd/compile/internal/gc/walk.go index a4fa607c8f..d6686ca5c3 100644 --- a/src/cmd/compile/internal/gc/walk.go +++ b/src/cmd/compile/internal/gc/walk.go @@ -2487,10 +2487,7 @@ func varexpr(n *Node) bool { return varexpr(n.Left) && varexpr(n.Right) case ODOT: // but not ODOTPTR - // The original code always returned false for ODOT, - // because n.Right would be an ONAME with n.Class not set. - // TODO(iant): Fix this to remove "&& false". - return varexpr(n.Left) && false + return varexpr(n.Left) } // Be conservative.