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cmd/compile: add x.Uses==1 test to load combiners
We need to make sure that when we combine loads, we only do so if there are no other uses of the load. We can't split one load into two because that can then lead to inconsistent loaded values in the presence of races. Add some aggressive copy removal code so that phantom "dead copy" uses of values are cleaned up promptly. This lets us use x.Uses==1 conditions reliably. Change-Id: I9037311db85665f3868dbeb3adb3de5c20728b38 Reviewed-on: https://go-review.googlesource.com/21853 Reviewed-by: Todd Neal <todd@tneal.org>
This commit is contained in:
parent
204b6f48c5
commit
cd85f711c0
@ -101,3 +101,5 @@ func TestPhi(t *testing.T) { runTest(t, "phi_ssa.go") }
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func TestSlice(t *testing.T) { runTest(t, "slice.go") }
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func TestNamedReturn(t *testing.T) { runTest(t, "namedReturn.go") }
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func TestDuplicateLoad(t *testing.T) { runTest(t, "dupLoad.go") }
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46
src/cmd/compile/internal/gc/testdata/dupLoad.go
vendored
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46
src/cmd/compile/internal/gc/testdata/dupLoad.go
vendored
Normal file
@ -0,0 +1,46 @@
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// run
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// Copyright 2016 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// This test makes sure that we don't split a single
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// load up into two separate loads.
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package main
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import "fmt"
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//go:noinline
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func read(b []byte) (uint16, uint16) {
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// There is only a single read of b[0]. The two
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// returned values must have the same low byte.
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v := b[0]
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return uint16(v), uint16(v) | uint16(b[1])<<8
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}
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const N = 100000
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func main() {
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done := make(chan struct{})
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b := make([]byte, 2)
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go func() {
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for i := 0; i < N; i++ {
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b[0] = byte(i)
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b[1] = byte(i)
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}
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done <- struct{}{}
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}()
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go func() {
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for i := 0; i < N; i++ {
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x, y := read(b)
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if byte(x) != byte(y) {
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fmt.Printf("x=%x y=%x\n", x, y)
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panic("bad")
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}
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}
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done <- struct{}{}
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}()
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<-done
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<-done
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}
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@ -1,5 +1,9 @@
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// run
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// Copyright 2016 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// This test makes sure that naming named
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// return variables in a return statement works.
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// See issue #14904.
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@ -1369,13 +1369,13 @@
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// There are many ways these combinations could occur. This is
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// designed to match the way encoding/binary.LittleEndian does it.
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(ORW x0:(MOVBload [i] {s} p mem)
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(SHLWconst [8] x1:(MOVBload [i+1] {s} p mem))) && mergePoint(b,x0,x1) != nil -> @mergePoint(b,x0,x1) (MOVWload [i] {s} p mem)
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(SHLWconst [8] x1:(MOVBload [i+1] {s} p mem))) && x0.Uses == 1 && x1.Uses == 1 && mergePoint(b,x0,x1) != nil -> @mergePoint(b,x0,x1) (MOVWload [i] {s} p mem)
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(ORL (ORL (ORL
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x0:(MOVBload [i] {s} p mem)
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(SHLLconst [8] x1:(MOVBload [i+1] {s} p mem)))
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(SHLLconst [16] x2:(MOVBload [i+2] {s} p mem)))
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(SHLLconst [24] x3:(MOVBload [i+3] {s} p mem))) && mergePoint(b,x0,x1,x2,x3) != nil -> @mergePoint(b,x0,x1,x2,x3) (MOVLload [i] {s} p mem)
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(SHLLconst [24] x3:(MOVBload [i+3] {s} p mem))) && x0.Uses == 1 && x1.Uses == 1 && x2.Uses == 1 && x3.Uses == 1 && mergePoint(b,x0,x1,x2,x3) != nil -> @mergePoint(b,x0,x1,x2,x3) (MOVLload [i] {s} p mem)
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(ORQ (ORQ (ORQ (ORQ (ORQ (ORQ (ORQ
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x0:(MOVBload [i] {s} p mem)
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@ -1385,16 +1385,16 @@
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(SHLQconst [32] x4:(MOVBload [i+4] {s} p mem)))
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(SHLQconst [40] x5:(MOVBload [i+5] {s} p mem)))
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(SHLQconst [48] x6:(MOVBload [i+6] {s} p mem)))
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(SHLQconst [56] x7:(MOVBload [i+7] {s} p mem))) && mergePoint(b,x0,x1,x2,x3,x4,x5,x6,x7) != nil -> @mergePoint(b,x0,x1,x2,x3,x4,x5,x6,x7) (MOVQload [i] {s} p mem)
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(SHLQconst [56] x7:(MOVBload [i+7] {s} p mem))) && x0.Uses == 1 && x1.Uses == 1 && x2.Uses == 1 && x3.Uses == 1 && x4.Uses == 1 && x5.Uses == 1 && x6.Uses == 1 && x7.Uses == 1 && mergePoint(b,x0,x1,x2,x3,x4,x5,x6,x7) != nil -> @mergePoint(b,x0,x1,x2,x3,x4,x5,x6,x7) (MOVQload [i] {s} p mem)
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(ORW x0:(MOVBloadidx1 [i] {s} p idx mem)
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(SHLWconst [8] x1:(MOVBloadidx1 [i+1] {s} p idx mem))) && mergePoint(b,x0,x1) != nil -> @mergePoint(b,x0,x1) (MOVWloadidx1 <v.Type> [i] {s} p idx mem)
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(SHLWconst [8] x1:(MOVBloadidx1 [i+1] {s} p idx mem))) && x0.Uses == 1 && x1.Uses == 1 && mergePoint(b,x0,x1) != nil -> @mergePoint(b,x0,x1) (MOVWloadidx1 <v.Type> [i] {s} p idx mem)
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(ORL (ORL (ORL
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x0:(MOVBloadidx1 [i] {s} p idx mem)
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(SHLLconst [8] x1:(MOVBloadidx1 [i+1] {s} p idx mem)))
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(SHLLconst [16] x2:(MOVBloadidx1 [i+2] {s} p idx mem)))
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(SHLLconst [24] x3:(MOVBloadidx1 [i+3] {s} p idx mem))) && mergePoint(b,x0,x1,x2,x3) != nil -> @mergePoint(b,x0,x1,x2,x3) (MOVLloadidx1 <v.Type> [i] {s} p idx mem)
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(SHLLconst [24] x3:(MOVBloadidx1 [i+3] {s} p idx mem))) && x0.Uses == 1 && x1.Uses == 1 && x2.Uses == 1 && x3.Uses == 1 && mergePoint(b,x0,x1,x2,x3) != nil -> @mergePoint(b,x0,x1,x2,x3) (MOVLloadidx1 <v.Type> [i] {s} p idx mem)
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(ORQ (ORQ (ORQ (ORQ (ORQ (ORQ (ORQ
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x0:(MOVBloadidx1 [i] {s} p idx mem)
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@ -1404,4 +1404,4 @@
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(SHLQconst [32] x4:(MOVBloadidx1 [i+4] {s} p idx mem)))
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(SHLQconst [40] x5:(MOVBloadidx1 [i+5] {s} p idx mem)))
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(SHLQconst [48] x6:(MOVBloadidx1 [i+6] {s} p idx mem)))
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(SHLQconst [56] x7:(MOVBloadidx1 [i+7] {s} p idx mem))) && mergePoint(b,x0,x1,x2,x3,x4,x5,x6,x7) != nil -> @mergePoint(b,x0,x1,x2,x3,x4,x5,x6,x7) (MOVQloadidx1 <v.Type> [i] {s} p idx mem)
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(SHLQconst [56] x7:(MOVBloadidx1 [i+7] {s} p idx mem))) && x0.Uses == 1 && x1.Uses == 1 && x2.Uses == 1 && x3.Uses == 1 && x4.Uses == 1 && x5.Uses == 1 && x6.Uses == 1 && x7.Uses == 1 && mergePoint(b,x0,x1,x2,x3,x4,x5,x6,x7) != nil -> @mergePoint(b,x0,x1,x2,x3,x4,x5,x6,x7) (MOVQloadidx1 <v.Type> [i] {s} p idx mem)
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@ -418,7 +418,7 @@ func TestNilcheckBug(t *testing.T) {
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Goto("exit")),
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Bloc("exit",
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Valu("phi", OpPhi, TypeMem, 0, nil, "mem", "store"),
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Exit("mem")))
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Exit("phi")))
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CheckFunc(fun.f)
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// we need the opt here to rewrite the user nilcheck
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@ -40,9 +40,44 @@ func applyRewrite(f *Func, rb func(*Block) bool, rv func(*Value, *Config) bool)
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}
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curb = nil
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for _, v := range b.Values {
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change = copyelimValue(v) || change
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change = phielimValue(v) || change
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// Eliminate copy inputs.
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// If any copy input becomes unused, mark it
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// as invalid and discard its argument. Repeat
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// recursively on the discarded argument.
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// This phase helps remove phantom "dead copy" uses
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// of a value so that a x.Uses==1 rule condition
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// fires reliably.
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for i, a := range v.Args {
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if a.Op != OpCopy {
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continue
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}
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x := a.Args[0]
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// Rewriting can generate OpCopy loops.
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// They are harmless (see removePredecessor),
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// but take care to stop if we find a cycle.
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slow := x // advances every other iteration
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var advance bool
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for x.Op == OpCopy {
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x = x.Args[0]
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if slow == x {
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break
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}
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if advance {
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slow = slow.Args[0]
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}
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advance = !advance
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}
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v.SetArg(i, x)
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change = true
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for a.Uses == 0 {
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b := a.Args[0]
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a.reset(OpInvalid)
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a = b
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}
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}
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// apply rewrite function
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curv = v
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if rv(v, config) {
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@ -52,7 +87,28 @@ func applyRewrite(f *Func, rb func(*Block) bool, rv func(*Value, *Config) bool)
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}
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}
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if !change {
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return
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break
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}
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}
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// remove clobbered copies
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for _, b := range f.Blocks {
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j := 0
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for i, v := range b.Values {
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if v.Op == OpInvalid {
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f.freeValue(v)
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continue
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}
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if i != j {
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b.Values[j] = v
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}
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j++
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}
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if j != len(b.Values) {
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tail := b.Values[j:]
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for j := range tail {
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tail[j] = nil
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}
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b.Values = b.Values[:j]
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}
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}
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}
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@ -12666,7 +12666,7 @@ func rewriteValueAMD64_OpAMD64ORL(v *Value, config *Config) bool {
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return true
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}
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// match: (ORL (ORL (ORL x0:(MOVBload [i] {s} p mem) (SHLLconst [8] x1:(MOVBload [i+1] {s} p mem))) (SHLLconst [16] x2:(MOVBload [i+2] {s} p mem))) (SHLLconst [24] x3:(MOVBload [i+3] {s} p mem)))
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// cond: mergePoint(b,x0,x1,x2,x3) != nil
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// cond: x0.Uses == 1 && x1.Uses == 1 && x2.Uses == 1 && x3.Uses == 1 && mergePoint(b,x0,x1,x2,x3) != nil
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// result: @mergePoint(b,x0,x1,x2,x3) (MOVLload [i] {s} p mem)
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for {
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v_0 := v.Args[0]
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@ -12754,7 +12754,7 @@ func rewriteValueAMD64_OpAMD64ORL(v *Value, config *Config) bool {
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if mem != x3.Args[1] {
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break
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}
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if !(mergePoint(b, x0, x1, x2, x3) != nil) {
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if !(x0.Uses == 1 && x1.Uses == 1 && x2.Uses == 1 && x3.Uses == 1 && mergePoint(b, x0, x1, x2, x3) != nil) {
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break
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}
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b = mergePoint(b, x0, x1, x2, x3)
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@ -12768,7 +12768,7 @@ func rewriteValueAMD64_OpAMD64ORL(v *Value, config *Config) bool {
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return true
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}
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// match: (ORL (ORL (ORL x0:(MOVBloadidx1 [i] {s} p idx mem) (SHLLconst [8] x1:(MOVBloadidx1 [i+1] {s} p idx mem))) (SHLLconst [16] x2:(MOVBloadidx1 [i+2] {s} p idx mem))) (SHLLconst [24] x3:(MOVBloadidx1 [i+3] {s} p idx mem)))
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// cond: mergePoint(b,x0,x1,x2,x3) != nil
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// cond: x0.Uses == 1 && x1.Uses == 1 && x2.Uses == 1 && x3.Uses == 1 && mergePoint(b,x0,x1,x2,x3) != nil
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// result: @mergePoint(b,x0,x1,x2,x3) (MOVLloadidx1 <v.Type> [i] {s} p idx mem)
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for {
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v_0 := v.Args[0]
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@ -12866,7 +12866,7 @@ func rewriteValueAMD64_OpAMD64ORL(v *Value, config *Config) bool {
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if mem != x3.Args[2] {
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break
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}
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if !(mergePoint(b, x0, x1, x2, x3) != nil) {
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if !(x0.Uses == 1 && x1.Uses == 1 && x2.Uses == 1 && x3.Uses == 1 && mergePoint(b, x0, x1, x2, x3) != nil) {
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break
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}
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b = mergePoint(b, x0, x1, x2, x3)
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@ -12980,7 +12980,7 @@ func rewriteValueAMD64_OpAMD64ORQ(v *Value, config *Config) bool {
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return true
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}
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// match: (ORQ (ORQ (ORQ (ORQ (ORQ (ORQ (ORQ x0:(MOVBload [i] {s} p mem) (SHLQconst [8] x1:(MOVBload [i+1] {s} p mem))) (SHLQconst [16] x2:(MOVBload [i+2] {s} p mem))) (SHLQconst [24] x3:(MOVBload [i+3] {s} p mem))) (SHLQconst [32] x4:(MOVBload [i+4] {s} p mem))) (SHLQconst [40] x5:(MOVBload [i+5] {s} p mem))) (SHLQconst [48] x6:(MOVBload [i+6] {s} p mem))) (SHLQconst [56] x7:(MOVBload [i+7] {s} p mem)))
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// cond: mergePoint(b,x0,x1,x2,x3,x4,x5,x6,x7) != nil
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// cond: x0.Uses == 1 && x1.Uses == 1 && x2.Uses == 1 && x3.Uses == 1 && x4.Uses == 1 && x5.Uses == 1 && x6.Uses == 1 && x7.Uses == 1 && mergePoint(b,x0,x1,x2,x3,x4,x5,x6,x7) != nil
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// result: @mergePoint(b,x0,x1,x2,x3,x4,x5,x6,x7) (MOVQload [i] {s} p mem)
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for {
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v_0 := v.Args[0]
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@ -13176,7 +13176,7 @@ func rewriteValueAMD64_OpAMD64ORQ(v *Value, config *Config) bool {
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if mem != x7.Args[1] {
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break
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}
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if !(mergePoint(b, x0, x1, x2, x3, x4, x5, x6, x7) != nil) {
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if !(x0.Uses == 1 && x1.Uses == 1 && x2.Uses == 1 && x3.Uses == 1 && x4.Uses == 1 && x5.Uses == 1 && x6.Uses == 1 && x7.Uses == 1 && mergePoint(b, x0, x1, x2, x3, x4, x5, x6, x7) != nil) {
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break
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}
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b = mergePoint(b, x0, x1, x2, x3, x4, x5, x6, x7)
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@ -13190,7 +13190,7 @@ func rewriteValueAMD64_OpAMD64ORQ(v *Value, config *Config) bool {
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return true
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}
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// match: (ORQ (ORQ (ORQ (ORQ (ORQ (ORQ (ORQ x0:(MOVBloadidx1 [i] {s} p idx mem) (SHLQconst [8] x1:(MOVBloadidx1 [i+1] {s} p idx mem))) (SHLQconst [16] x2:(MOVBloadidx1 [i+2] {s} p idx mem))) (SHLQconst [24] x3:(MOVBloadidx1 [i+3] {s} p idx mem))) (SHLQconst [32] x4:(MOVBloadidx1 [i+4] {s} p idx mem))) (SHLQconst [40] x5:(MOVBloadidx1 [i+5] {s} p idx mem))) (SHLQconst [48] x6:(MOVBloadidx1 [i+6] {s} p idx mem))) (SHLQconst [56] x7:(MOVBloadidx1 [i+7] {s} p idx mem)))
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// cond: mergePoint(b,x0,x1,x2,x3,x4,x5,x6,x7) != nil
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// cond: x0.Uses == 1 && x1.Uses == 1 && x2.Uses == 1 && x3.Uses == 1 && x4.Uses == 1 && x5.Uses == 1 && x6.Uses == 1 && x7.Uses == 1 && mergePoint(b,x0,x1,x2,x3,x4,x5,x6,x7) != nil
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// result: @mergePoint(b,x0,x1,x2,x3,x4,x5,x6,x7) (MOVQloadidx1 <v.Type> [i] {s} p idx mem)
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for {
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v_0 := v.Args[0]
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@ -13408,7 +13408,7 @@ func rewriteValueAMD64_OpAMD64ORQ(v *Value, config *Config) bool {
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if mem != x7.Args[2] {
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break
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}
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if !(mergePoint(b, x0, x1, x2, x3, x4, x5, x6, x7) != nil) {
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if !(x0.Uses == 1 && x1.Uses == 1 && x2.Uses == 1 && x3.Uses == 1 && x4.Uses == 1 && x5.Uses == 1 && x6.Uses == 1 && x7.Uses == 1 && mergePoint(b, x0, x1, x2, x3, x4, x5, x6, x7) != nil) {
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break
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}
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b = mergePoint(b, x0, x1, x2, x3, x4, x5, x6, x7)
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@ -13514,7 +13514,7 @@ func rewriteValueAMD64_OpAMD64ORW(v *Value, config *Config) bool {
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return true
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}
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// match: (ORW x0:(MOVBload [i] {s} p mem) (SHLWconst [8] x1:(MOVBload [i+1] {s} p mem)))
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// cond: mergePoint(b,x0,x1) != nil
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// cond: x0.Uses == 1 && x1.Uses == 1 && mergePoint(b,x0,x1) != nil
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// result: @mergePoint(b,x0,x1) (MOVWload [i] {s} p mem)
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for {
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x0 := v.Args[0]
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@ -13548,7 +13548,7 @@ func rewriteValueAMD64_OpAMD64ORW(v *Value, config *Config) bool {
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if mem != x1.Args[1] {
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break
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}
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if !(mergePoint(b, x0, x1) != nil) {
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if !(x0.Uses == 1 && x1.Uses == 1 && mergePoint(b, x0, x1) != nil) {
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break
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}
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b = mergePoint(b, x0, x1)
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@ -13562,7 +13562,7 @@ func rewriteValueAMD64_OpAMD64ORW(v *Value, config *Config) bool {
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return true
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}
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// match: (ORW x0:(MOVBloadidx1 [i] {s} p idx mem) (SHLWconst [8] x1:(MOVBloadidx1 [i+1] {s} p idx mem)))
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// cond: mergePoint(b,x0,x1) != nil
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// cond: x0.Uses == 1 && x1.Uses == 1 && mergePoint(b,x0,x1) != nil
|
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// result: @mergePoint(b,x0,x1) (MOVWloadidx1 <v.Type> [i] {s} p idx mem)
|
||||
for {
|
||||
x0 := v.Args[0]
|
||||
@ -13600,7 +13600,7 @@ func rewriteValueAMD64_OpAMD64ORW(v *Value, config *Config) bool {
|
||||
if mem != x1.Args[2] {
|
||||
break
|
||||
}
|
||||
if !(mergePoint(b, x0, x1) != nil) {
|
||||
if !(x0.Uses == 1 && x1.Uses == 1 && mergePoint(b, x0, x1) != nil) {
|
||||
break
|
||||
}
|
||||
b = mergePoint(b, x0, x1)
|
||||
|
Loading…
Reference in New Issue
Block a user