runtime: teach peephole optimizer that duffcopy clobbers X0

Duffcopy now uses X0, as of 5cf281a.  Teach the peephole
optimizer that duffcopy clobbers X0 so that it does not
rename registers use X0 across the duffcopy instruction.

Fixes #13171

Change-Id: I389cbf1982cb6eb2f51e6152ac96736a8589f085
Reviewed-on: https://go-review.googlesource.com/16715
Run-TryBot: Keith Randall <khr@golang.org>
Reviewed-by: Minux Ma <minux@golang.org>
Reviewed-by: Ilya Tocar <ilya.tocar@intel.com>

diff --git a/src/cmd/compile/internal/amd64/peep.go b/src/cmd/compile/internal/amd64/peep.go
index 130f369a8b657be4a642caccef7036ccd3786b82..452f954bd828c881e64adf082527543c89588559 100644 (file)
--- a/src/cmd/compile/internal/amd64/peep.go
+++ b/src/cmd/compile/internal/amd64/peep.go
@@ -823,6 +823,10 @@ func copyu(p *obj.Prog, v *obj.Addr, s *obj.Addr) int {
                return 2
        }
 
+       if (p.Info.Reguse|p.Info.Regset)&FtoB(int(v.Reg)) != 0 {
+               return 2
+       }
+
        if p.Info.Flags&gc.LeftAddr != 0 {
                if copyas(&p.From, v) {
                        return 2

diff --git a/src/cmd/compile/internal/amd64/prog.go b/src/cmd/compile/internal/amd64/prog.go
index eff6ccee5b3bc9ca2e15632f56cffcbd0abda6ed..ae8f5255a968a4fb40f437c20f3b0450bce1a8cf 100644 (file)
--- a/src/cmd/compile/internal/amd64/prog.go
+++ b/src/cmd/compile/internal/amd64/prog.go
@@ -140,7 +140,7 @@ var progtable = [x86.ALAST]obj.ProgInfo{
        x86.AMOVSL:     {Flags: gc.OK, Reguse: DI | SI, Regset: DI | SI},
        x86.AMOVSQ:     {Flags: gc.OK, Reguse: DI | SI, Regset: DI | SI},
        x86.AMOVSW:     {Flags: gc.OK, Reguse: DI | SI, Regset: DI | SI},
-       obj.ADUFFCOPY:  {Flags: gc.OK, Reguse: DI | SI, Regset: DI | SI | CX},
+       obj.ADUFFCOPY:  {Flags: gc.OK, Reguse: DI | SI, Regset: DI | SI | X0},
        x86.AMOVSD:     {Flags: gc.SizeD | gc.LeftRead | gc.RightWrite | gc.Move},
        x86.AMOVSS:     {Flags: gc.SizeF | gc.LeftRead | gc.RightWrite | gc.Move},
 

diff --git a/src/cmd/compile/internal/amd64/reg.go b/src/cmd/compile/internal/amd64/reg.go
index 8fab6399b1d88c86a08ca92b980eade55f7b0b95..60822fbfe99558c70536645c68c7b99cd5537476 100644 (file)
--- a/src/cmd/compile/internal/amd64/reg.go
+++ b/src/cmd/compile/internal/amd64/reg.go
@@ -107,6 +107,7 @@ const (
        DI  = 1 << (x86.REG_DI - x86.REG_AX)
        SI  = 1 << (x86.REG_SI - x86.REG_AX)
        R15 = 1 << (x86.REG_R15 - x86.REG_AX)
+       X0  = 1 << 16
 )
 
 func RtoB(r int) uint64 {

diff --git a/test/fixedbugs/issue13171.go b/test/fixedbugs/issue13171.go
new file mode 100644 (file)
index 0000000..5d127a5
--- /dev/null
+++ b/test/fixedbugs/issue13171.go
@@ -0,0 +1,34 @@
+// run
+
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+// Make sure the compiler knows that DUFFCOPY clobbers X0
+
+import "fmt"
+
+//go:noinline
+func f(x float64) float64 {
+       // y is allocated to X0
+       y := x + 5
+       // marshals z before y.  Marshalling z
+       // calls DUFFCOPY.
+       return g(z, y)
+}
+
+//go:noinline
+func g(b [64]byte, y float64) float64 {
+       return y
+}
+
+var z [64]byte
+
+func main() {
+       got := f(5)
+       if got != 10 {
+               panic(fmt.Sprintf("want 10, got %f", got))
+       }
+}