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Revert "cmd/compile: enhance tighten pass for memory values"

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This reverts CL 458755.

Reason for revert: broke make.bash on GOAMD64=v3:

/workdir/go/src/crypto/sha1/sha1.go:54:35: internal compiler error: '(*digest).MarshalBinary': func (*digest).MarshalBinary, startMem[b13] has different values, old v206, new v338

goroutine 34 [running]:
runtime/debug.Stack()
	/workdir/go/src/runtime/debug/stack.go:24 +0x9f
bootstrap/cmd/compile/internal/base.FatalfAt({0x13, 0xaa0f1}, {0xc000db4440, 0x40}, {0xc0013b0000, 0x5, 0x5})
	/workdir/go/src/cmd/compile/internal/base/print.go:234 +0x2d1
bootstrap/cmd/compile/internal/base.Fatalf(...)
	/workdir/go/src/cmd/compile/internal/base/print.go:203
bootstrap/cmd/compile/internal/ssagen.(*ssafn).Fatalf(0xc000d90000, {0x13, 0xaa0f1}, {0xcb7b91, 0x3a}, {0xc000d99bc0, 0x4, 0x4})
	/workdir/go/src/cmd/compile/internal/ssagen/ssa.go:7896 +0x1f8
bootstrap/cmd/compile/internal/ssa.(*Func).Fatalf(0xc000d82340, {0xcb7b91, 0x3a}, {0xc000d99bc0, 0x4, 0x4})
	/workdir/go/src/cmd/compile/internal/ssa/func.go:716 +0x342
bootstrap/cmd/compile/internal/ssa.memState(0xc000d82340, {0xc000ec6200, 0x22, 0x40}, {0xc001046000, 0x22, 0x40})
	/workdir/go/src/cmd/compile/internal/ssa/tighten.go:240 +0x6c5
bootstrap/cmd/compile/internal/ssa.tighten(0xc000d82340)
[...]

Change-Id: Ic445fb48fe0f2c60ac67abe259b66594f1419152
Reviewed-on: https://go-review.googlesource.com/c/go/+/492335
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Reviewed-by: David Chase <drchase@google.com>
This commit is contained in:
Daniel Martí 2023-05-03 20:56:41 +00:00
parent 129b597de3
commit aa6e168480
3 changed files with 7 additions and 127 deletions
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7
src/cmd/compile/internal/ssa/regalloc.go
View File

@ -602,11 +602,6 @@ func isLeaf(f *Func) bool {
return true return true
} }
// needRegister reports whether v needs a register.
func (v *Value) needRegister() bool {
return !v.Type.IsMemory() && !v.Type.IsVoid() && !v.Type.IsFlags() && !v.Type.IsTuple()
}
func (s *regAllocState) init(f *Func) { func (s *regAllocState) init(f *Func) {
s.f = f s.f = f
s.f.RegAlloc = s.f.Cache.locs[:0] s.f.RegAlloc = s.f.Cache.locs[:0]
@ -707,7 +702,7 @@ func (s *regAllocState) init(f *Func) {
s.copies = make(map[*Value]bool) s.copies = make(map[*Value]bool)
for _, b := range s.visitOrder { for _, b := range s.visitOrder {
for _, v := range b.Values { for _, v := range b.Values {
if v.needRegister() { if !v.Type.IsMemory() && !v.Type.IsVoid() && !v.Type.IsFlags() && !v.Type.IsTuple() {
s.values[v.ID].needReg = true s.values[v.ID].needReg = true
s.values[v.ID].rematerializeable = v.rematerializeable() s.values[v.ID].rematerializeable = v.rematerializeable()
s.orig[v.ID] = v s.orig[v.ID] = v

105
src/cmd/compile/internal/ssa/tighten.go
View File

@ -21,14 +21,6 @@ func tighten(f *Func) {
canMove := f.Cache.allocBoolSlice(f.NumValues()) canMove := f.Cache.allocBoolSlice(f.NumValues())
defer f.Cache.freeBoolSlice(canMove) defer f.Cache.freeBoolSlice(canMove)
// Compute the memory states of each block.
startMem := f.Cache.allocValueSlice(f.NumBlocks())
defer f.Cache.freeValueSlice(startMem)
endMem := f.Cache.allocValueSlice(f.NumBlocks())
defer f.Cache.freeValueSlice(endMem)
memState(f, startMem, endMem)
for _, b := range f.Blocks { for _, b := range f.Blocks {
for _, v := range b.Values { for _, v := range b.Values {
if v.Op.isLoweredGetClosurePtr() { if v.Op.isLoweredGetClosurePtr() {
@ -43,12 +35,15 @@ func tighten(f *Func) {
// SelectN is typically, ultimately, a register. // SelectN is typically, ultimately, a register.
continue continue
} }
if v.MemoryArg() != nil {
// We can't move values which have a memory arg - it might
// make two memory values live across a block boundary.
continue
}
// Count arguments which will need a register. // Count arguments which will need a register.
narg := 0 narg := 0
for _, a := range v.Args { for _, a := range v.Args {
// SP and SB are special registers and have no effect on if !a.rematerializeable() {
// the allocation of general-purpose registers.
if a.needRegister() && a.Op != OpSB && a.Op != OpSP {
narg++ narg++
} }
} }
@ -143,16 +138,6 @@ func tighten(f *Func) {
// v is not moveable, or is already in correct place. // v is not moveable, or is already in correct place.
continue continue
} }
if mem := v.MemoryArg(); mem != nil {
if startMem[t.ID] != mem {
// We can't move a value with a memory arg unless the target block
// has that memory arg as its starting memory.
continue
}
}
if f.pass.debug > 0 {
b.Func.Warnl(v.Pos, "%v is moved", v.Op)
}
// Move v to the block which dominates its uses. // Move v to the block which dominates its uses.
t.Values = append(t.Values, v) t.Values = append(t.Values, v)
v.Block = t v.Block = t
@ -189,81 +174,3 @@ func phiTighten(f *Func) {
} }
} }
} }
// memState computes the memory state at the beginning and end of each block of
// the function. The memory state is represented by a value of mem type.
// The returned result is stored in startMem and endMem, and endMem is nil for
// blocks with no successors (Exit,Ret,RetJmp blocks). This algorithm is not
// suitable for infinite loop blocks that do not contain any mem operations.
// For example:
// b1:
//
// (some values)
//
// plain -> b2
// b2: <- b1 b2
// Plain -> b2
//
// Algorithm introduction:
// 1. The start memory state of a block is InitMem, a Phi node of type mem or
// an incoming memory value.
// 2. The start memory state of a block is consistent with the end memory state
// of its parent nodes. If the start memory state of a block is a Phi value,
// then the end memory state of its parent nodes is consistent with the
// corresponding argument value of the Phi node.
// 3. The algorithm first obtains the memory state of some blocks in the tree
// in the first step. Then floods the known memory state to other nodes in
// the second step.
func memState(f *Func, startMem, endMem []*Value) {
// This slice contains the set of blocks that have had their startMem set but this
// startMem value has not yet been propagated to the endMem of its predecessors
changed := make([]*Block, 0)
// First step, init the memory state of some blocks.
for _, b := range f.Blocks {
for _, v := range b.Values {
var mem *Value
if v.Op == OpPhi {
if v.Type.IsMemory() {
mem = v
}
} else if v.Op == OpInitMem {
mem = v // This is actually not needed.
} else if a := v.MemoryArg(); a != nil && a.Block != b {
// The only incoming memory value doesn't belong to this block.
mem = a
}
if mem != nil {
if old := startMem[b.ID]; old != nil {
if old == mem {
continue
}
f.Fatalf("func %s, startMem[%v] has different values, old %v, new %v", f.Name, b, old, mem)
}
startMem[b.ID] = mem
changed = append(changed, b)
}
}
}
// Second step, floods the known memory state of some blocks to others.
for len(changed) != 0 {
top := changed[0]
changed = changed[1:]
mem := startMem[top.ID]
for i, p := range top.Preds {
pb := p.b
if endMem[pb.ID] != nil {
continue
}
if mem.Op == OpPhi && mem.Block == top {
endMem[pb.ID] = mem.Args[i]
} else {
endMem[pb.ID] = mem
}
if startMem[pb.ID] == nil {
startMem[pb.ID] = endMem[pb.ID]
changed = append(changed, pb)
}
}
}
}

22
test/tighten.go
View File

@ -1,22 +0,0 @@
// errorcheck -0 -d=ssa/tighten/debug=1
//go:build arm64
// Copyright 2023 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
var (
e any
ts uint16
)
func moveValuesWithMemoryArg(len int) {
for n := 0; n < len; n++ {
// Load of e.data is lowed as a MOVDload op, which has a memory
// argument. It's moved near where it's used.
_ = e != ts // ERROR "MOVDload is moved$" "MOVDaddr is moved$"
}
}