cmd/internal/gc: fix write barrier fast path on RISC architectures

They have to read the boolean into a register first and then do
the comparison.

Fixes #10598.

Change-Id: I2b808837a8c6393e1e0778296b6592aaab2b04bf
Signed-off-by: Shenghou Ma <minux@golang.org>
Reviewed-on: https://go-review.googlesource.com/9453
Reviewed-by: Dave Cheney <dave@cheney.net>

diff --git a/src/cmd/internal/gc/cgen.go b/src/cmd/internal/gc/cgen.go
index 3fea97e0a61b587100f5a529c701de4362d544c9..574d24f3028c5e8ed9197e44f6ec6562737c5d40 100644 (file)
--- a/src/cmd/internal/gc/cgen.go
+++ b/src/cmd/internal/gc/cgen.go
@@ -803,7 +803,19 @@ func cgen_wbptr(n, res *Node) {
                Cgenr(n, &src, nil)
        }
 
-       Thearch.Gins(Thearch.Optoas(OCMP, Types[TUINT8]), syslook("writeBarrierEnabled", 0), Nodintconst(0))
+       wbEnabled := syslook("writeBarrierEnabled", 0)
+       switch Ctxt.Arch.Thechar {
+       default:
+               Fatal("cgen_wbptr: unknown architecture")
+       case '5', '7', '9':
+               var tmp Node
+               Regalloc(&tmp, Types[TUINT8], nil)
+               Thearch.Gmove(wbEnabled, &tmp)
+               Thearch.Gins(Thearch.Optoas(OCMP, Types[TUINT8]), &tmp, Nodintconst(0))
+               Regfree(&tmp)
+       case '6', '8':
+               Thearch.Gins(Thearch.Optoas(OCMP, Types[TUINT8]), wbEnabled, Nodintconst(0))
+       }
        pbr := Gbranch(Thearch.Optoas(ONE, Types[TUINT8]), nil, -1)
        Thearch.Gins(Thearch.Optoas(OAS, Types[Tptr]), &src, &dst)
        pjmp := Gbranch(obj.AJMP, nil, 0)