diff options
| author | Michael Hudson-Doyle <michael.hudson@canonical.com> | 2017-04-27 11:56:42 +1200 |
|---|---|---|
| committer | Russ Cox <rsc@golang.org> | 2017-10-25 18:57:16 +0000 |
| commit | b838f943ab3e3cb46e386e4541f0f1d2226c7958 (patch) | |
| tree | a6e0efa5d845d17ad9b376a5c3e93d68c6897572 | |
| parent | 3be9637d5658535714baeed1994af39342c5066c (diff) | |
| download | go-git-b838f943ab3e3cb46e386e4541f0f1d2226c7958.tar.gz | |
[release-branch.go1.8] cmd/internal/obj/x86: use LEAx rather than ADDx when calling DUFFxxxx via GOT
DUFFZERO on 386 is not marked as clobbering flags, but rewriteToUseGot rewrote
"ADUFFZERO $offset" to "MOVL runtime.duffxxx@GOT, CX; ADDL $offset, CX; CALL CX"
which does. Luckily the fix is easier than figuring out what the problem was:
replace the ADDL $offset, CX with LEAL $offset(CX), CX.
On amd64 DUFFZERO clobbers flags, on arm, arm64 and ppc64 ADD does not clobber
flags and s390x does not use the duff functions, so I'm fairly confident this
is the only fix required.
I don't know how to write a test though.
Change-Id: I69b0958f5f45771d61db5f5ecb4ded94e8960d4d
Reviewed-on: https://go-review.googlesource.com/41821
Run-TryBot: Michael Hudson-Doyle <michael.hudson@canonical.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-on: https://go-review.googlesource.com/70871
Run-TryBot: Russ Cox <rsc@golang.org>
| -rw-r--r-- | src/cmd/internal/obj/x86/obj6.go | 13 |
1 files changed, 7 insertions, 6 deletions
diff --git a/src/cmd/internal/obj/x86/obj6.go b/src/cmd/internal/obj/x86/obj6.go index eb6f867ca7..f3dfd32979 100644 --- a/src/cmd/internal/obj/x86/obj6.go +++ b/src/cmd/internal/obj/x86/obj6.go @@ -322,15 +322,13 @@ func progedit(ctxt *obj.Link, p *obj.Prog) { // Rewrite p, if necessary, to access global data via the global offset table. func rewriteToUseGot(ctxt *obj.Link, p *obj.Prog) { - var add, lea, mov obj.As + var lea, mov obj.As var reg int16 if p.Mode == 64 { - add = AADDQ lea = ALEAQ mov = AMOVQ reg = REG_R15 } else { - add = AADDL lea = ALEAL mov = AMOVL reg = REG_CX @@ -347,8 +345,10 @@ func rewriteToUseGot(ctxt *obj.Link, p *obj.Prog) { // ADUFFxxx $offset // becomes // $MOV runtime.duffxxx@GOT, $reg - // $ADD $offset, $reg + // $LEA $offset($reg), $reg // CALL $reg + // (we use LEAx rather than ADDx because ADDx clobbers + // flags and duffzero on 386 does not otherwise do so) var sym *obj.LSym if p.As == obj.ADUFFZERO { sym = obj.Linklookup(ctxt, "runtime.duffzero", 0) @@ -365,9 +365,10 @@ func rewriteToUseGot(ctxt *obj.Link, p *obj.Prog) { p.To.Offset = 0 p.To.Sym = nil p1 := obj.Appendp(ctxt, p) - p1.As = add - p1.From.Type = obj.TYPE_CONST + p1.As = lea + p1.From.Type = obj.TYPE_MEM p1.From.Offset = offset + p1.From.Reg = reg p1.To.Type = obj.TYPE_REG p1.To.Reg = reg p2 := obj.Appendp(ctxt, p1) |