155 lines
6.2 KiB
Diff
155 lines
6.2 KiB
Diff
From 27d5fccd2119099c70ab6a4418626beac7a97b4b Mon Sep 17 00:00:00 2001
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From: Keith Randall <khr@golang.org>
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Date: Thu, 7 Jan 2021 14:57:53 -0800
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Subject: [PATCH 04/44] [release-branch.go1.15] cmd/compile: don't
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short-circuit copies whose source is volatile
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Current optimization: When we copy a->b and then b->c, we might as well
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copy a->c instead of b->c (then b might be dead and go away).
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*Except* if a is a volatile location (might be clobbered by a call).
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In that case, we really do want to copy a immediately, because there
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might be a call before we can do the a->c copy.
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User calls can't happen in between, because the rule matches up the
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memory states. But calls inserted for memory barriers, particularly
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runtime.typedmemmove, can.
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(I guess we could introduce a register-calling-convention version
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of runtime.typedmemmove, but that seems a bigger change than this one.)
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Fixes #43575
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Change-Id: Ifa518bb1a6f3a8dd46c352d4fd54ea9713b3eb1a
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Reviewed-on: https://go-review.googlesource.com/c/go/+/282492
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Trust: Keith Randall <khr@golang.org>
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Trust: Josh Bleecher Snyder <josharian@gmail.com>
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Run-TryBot: Keith Randall <khr@golang.org>
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TryBot-Result: Go Bot <gobot@golang.org>
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Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>
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(cherry picked from commit 304f769ffc68e64244266b3aadbf91e6738c0064)
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Reviewed-on: https://go-review.googlesource.com/c/go/+/282558
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Trust: Dmitri Shuralyov <dmitshur@golang.org>
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Conflict:NA
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Reference:https://github.com/golang/go/commit/27d5fccd2119099c70ab6a4418626beac7a97b4b
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---
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.../compile/internal/ssa/gen/generic.rules | 4 +-
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.../compile/internal/ssa/rewritegeneric.go | 8 ++--
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test/fixedbugs/issue43570.go | 40 +++++++++++++++++++
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3 files changed, 46 insertions(+), 6 deletions(-)
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create mode 100644 test/fixedbugs/issue43570.go
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diff --git a/src/cmd/compile/internal/ssa/gen/generic.rules b/src/cmd/compile/internal/ssa/gen/generic.rules
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index ed5bfc81fd..8bbe913380 100644
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--- a/src/cmd/compile/internal/ssa/gen/generic.rules
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+++ b/src/cmd/compile/internal/ssa/gen/generic.rules
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@@ -2404,7 +2404,7 @@
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(Move {t1} [s] dst tmp1 midmem:(Move {t2} [s] tmp2 src _))
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&& t1.Compare(t2) == types.CMPeq
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&& isSamePtr(tmp1, tmp2)
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- && isStackPtr(src)
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+ && isStackPtr(src) && !isVolatile(src)
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&& disjoint(src, s, tmp2, s)
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&& (disjoint(src, s, dst, s) || isInlinableMemmove(dst, src, s, config))
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=> (Move {t1} [s] dst src midmem)
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@@ -2413,7 +2413,7 @@
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(Move {t1} [s] dst tmp1 midmem:(VarDef (Move {t2} [s] tmp2 src _)))
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&& t1.Compare(t2) == types.CMPeq
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&& isSamePtr(tmp1, tmp2)
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- && isStackPtr(src)
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+ && isStackPtr(src) && !isVolatile(src)
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&& disjoint(src, s, tmp2, s)
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&& (disjoint(src, s, dst, s) || isInlinableMemmove(dst, src, s, config))
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=> (Move {t1} [s] dst src midmem)
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diff --git a/src/cmd/compile/internal/ssa/rewritegeneric.go b/src/cmd/compile/internal/ssa/rewritegeneric.go
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index 9f4e1b95bd..6a09616aad 100644
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--- a/src/cmd/compile/internal/ssa/rewritegeneric.go
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+++ b/src/cmd/compile/internal/ssa/rewritegeneric.go
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@@ -13666,7 +13666,7 @@ func rewriteValuegeneric_OpMove(v *Value) bool {
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return true
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}
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// match: (Move {t1} [s] dst tmp1 midmem:(Move {t2} [s] tmp2 src _))
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- // cond: t1.Compare(t2) == types.CMPeq && isSamePtr(tmp1, tmp2) && isStackPtr(src) && disjoint(src, s, tmp2, s) && (disjoint(src, s, dst, s) || isInlinableMemmove(dst, src, s, config))
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+ // cond: t1.Compare(t2) == types.CMPeq && isSamePtr(tmp1, tmp2) && isStackPtr(src) && !isVolatile(src) && disjoint(src, s, tmp2, s) && (disjoint(src, s, dst, s) || isInlinableMemmove(dst, src, s, config))
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// result: (Move {t1} [s] dst src midmem)
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for {
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s := auxIntToInt64(v.AuxInt)
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@@ -13680,7 +13680,7 @@ func rewriteValuegeneric_OpMove(v *Value) bool {
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t2 := auxToType(midmem.Aux)
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src := midmem.Args[1]
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tmp2 := midmem.Args[0]
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- if !(t1.Compare(t2) == types.CMPeq && isSamePtr(tmp1, tmp2) && isStackPtr(src) && disjoint(src, s, tmp2, s) && (disjoint(src, s, dst, s) || isInlinableMemmove(dst, src, s, config))) {
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+ if !(t1.Compare(t2) == types.CMPeq && isSamePtr(tmp1, tmp2) && isStackPtr(src) && !isVolatile(src) && disjoint(src, s, tmp2, s) && (disjoint(src, s, dst, s) || isInlinableMemmove(dst, src, s, config))) {
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break
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}
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v.reset(OpMove)
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@@ -13690,7 +13690,7 @@ func rewriteValuegeneric_OpMove(v *Value) bool {
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return true
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}
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// match: (Move {t1} [s] dst tmp1 midmem:(VarDef (Move {t2} [s] tmp2 src _)))
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- // cond: t1.Compare(t2) == types.CMPeq && isSamePtr(tmp1, tmp2) && isStackPtr(src) && disjoint(src, s, tmp2, s) && (disjoint(src, s, dst, s) || isInlinableMemmove(dst, src, s, config))
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+ // cond: t1.Compare(t2) == types.CMPeq && isSamePtr(tmp1, tmp2) && isStackPtr(src) && !isVolatile(src) && disjoint(src, s, tmp2, s) && (disjoint(src, s, dst, s) || isInlinableMemmove(dst, src, s, config))
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// result: (Move {t1} [s] dst src midmem)
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for {
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s := auxIntToInt64(v.AuxInt)
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@@ -13708,7 +13708,7 @@ func rewriteValuegeneric_OpMove(v *Value) bool {
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t2 := auxToType(midmem_0.Aux)
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src := midmem_0.Args[1]
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tmp2 := midmem_0.Args[0]
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- if !(t1.Compare(t2) == types.CMPeq && isSamePtr(tmp1, tmp2) && isStackPtr(src) && disjoint(src, s, tmp2, s) && (disjoint(src, s, dst, s) || isInlinableMemmove(dst, src, s, config))) {
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+ if !(t1.Compare(t2) == types.CMPeq && isSamePtr(tmp1, tmp2) && isStackPtr(src) && !isVolatile(src) && disjoint(src, s, tmp2, s) && (disjoint(src, s, dst, s) || isInlinableMemmove(dst, src, s, config))) {
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break
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}
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v.reset(OpMove)
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diff --git a/test/fixedbugs/issue43570.go b/test/fixedbugs/issue43570.go
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new file mode 100644
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index 0000000000..d073fde5f6
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--- /dev/null
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+++ b/test/fixedbugs/issue43570.go
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@@ -0,0 +1,40 @@
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+// run
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+
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+// Copyright 2021 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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+
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+package main
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+
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+import "fmt"
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+
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+type T [8]*int
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+
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+//go:noinline
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+func f(x int) T {
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+ return T{}
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+}
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+
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+//go:noinline
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+func g(x int, t T) {
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+ if t != (T{}) {
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+ panic(fmt.Sprintf("bad: %v", t))
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+ }
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+}
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+
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+func main() {
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+ const N = 10000
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+ var q T
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+ func() {
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+ for i := 0; i < N; i++ {
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+ q = f(0)
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+ g(0, q)
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+ sink = make([]byte, 1024)
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+ }
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+ }()
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+ // Note that the closure is a trick to get the write to q to be a
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+ // write to a pointer that is known to be non-nil and requires
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+ // a write barrier.
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+}
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+
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+var sink []byte
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--
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2.27.0
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