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[dev.regabi] cmd/compile: refactor temp construction in walk

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This CL adds a few new helper functions for constructing and
initializing temporary variables during walk.

Passes toolstash -cmp.

Change-Id: I54965d992cd8dfef7cb7dc92a17c88372e52a0d6
Reviewed-on: https://go-review.googlesource.com/c/go/+/284224
Trust: Matthew Dempsky <mdempsky@google.com>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>
This commit is contained in:
Matthew Dempsky 2021-01-16 18:25:00 -08:00
parent 78e5aabcdb
commit ba0e8a92fa
5 changed files with 63 additions and 45 deletions
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13
src/cmd/compile/internal/walk/builtin.go
View File

@ -277,10 +277,8 @@ func walkMakeMap(n *ir.MakeExpr, init *ir.Nodes) ir.Node {
// Allocate hmap on stack.
// var hv hmap
hv := typecheck.Temp(hmapType)
init.Append(typecheck.Stmt(ir.NewAssignStmt(base.Pos, hv, nil)))
// h = &hv
h = typecheck.NodAddr(hv)
h = stackTempAddr(init, hmapType)
// Allocate one bucket pointed to by hmap.buckets on stack if hint
// is not larger than BUCKETSIZE. In case hint is larger than
@ -303,11 +301,8 @@ func walkMakeMap(n *ir.MakeExpr, init *ir.Nodes) ir.Node {
nif.Likely = true
// var bv bmap
bv := typecheck.Temp(reflectdata.MapBucketType(t))
nif.Body.Append(ir.NewAssignStmt(base.Pos, bv, nil))
// b = &bv
b := typecheck.NodAddr(bv)
b := stackTempAddr(&nif.Body, reflectdata.MapBucketType(t))
// h.buckets = b
bsym := hmapType.Field(5).Sym // hmap.buckets see reflect.go:hmap
@ -509,9 +504,7 @@ func walkNew(n *ir.UnaryExpr, init *ir.Nodes) ir.Node {
if t.Size() >= ir.MaxImplicitStackVarSize {
base.Fatalf("large ONEW with EscNone: %v", n)
}
r := typecheck.Temp(t)
init.Append(typecheck.Stmt(ir.NewAssignStmt(base.Pos, r, nil))) // zero temp
return typecheck.Expr(typecheck.NodAddr(r))
return stackTempAddr(init, t)
}
types.CalcSize(t)
n.MarkNonNil()

31
src/cmd/compile/internal/walk/complit.go
View File

@ -344,30 +344,14 @@ func slicelit(ctxt initContext, n *ir.CompLitExpr, var_ ir.Node, init *ir.Nodes)
if !types.Identical(t, x.Type()) {
panic("dotdotdot base type does not match order's assigned type")
}
if vstat == nil {
a = ir.NewAssignStmt(base.Pos, x, nil)
a = typecheck.Stmt(a)
init.Append(a) // zero new temp
} else {
// Declare that we're about to initialize all of x.
// (Which happens at the *vauto = vstat below.)
init.Append(ir.NewUnaryExpr(base.Pos, ir.OVARDEF, x))
}
a = typecheck.NodAddr(x)
a = initStackTemp(init, x, vstat != nil)
} else if n.Esc() == ir.EscNone {
a = typecheck.Temp(t)
if vstat == nil {
a = ir.NewAssignStmt(base.Pos, typecheck.Temp(t), nil)
a = typecheck.Stmt(a)
init.Append(a) // zero new temp
a = a.(*ir.AssignStmt).X
} else {
init.Append(ir.NewUnaryExpr(base.Pos, ir.OVARDEF, a))
// TODO(mdempsky): Remove this useless temporary.
// It's only needed to keep toolstash happy.
typecheck.Temp(t)
}
a = typecheck.NodAddr(a)
a = initStackTemp(init, typecheck.Temp(t), vstat != nil)
} else {
a = ir.NewUnaryExpr(base.Pos, ir.ONEW, ir.TypeNode(t))
}
@ -550,9 +534,8 @@ func anylit(n ir.Node, var_ ir.Node, init *ir.Nodes) {
var r ir.Node
if n.Prealloc != nil {
// n.Right is stack temporary used as backing store.
appendWalkStmt(init, ir.NewAssignStmt(base.Pos, n.Prealloc, nil)) // zero backing store, just in case (#18410)
r = typecheck.NodAddr(n.Prealloc)
// n.Prealloc is stack temporary used as backing store.
r = initStackTemp(init, n.Prealloc, false)
} else {
r = ir.NewUnaryExpr(base.Pos, ir.ONEW, ir.TypeNode(n.X.Type()))
r.SetEsc(n.Esc())

14
src/cmd/compile/internal/walk/convert.go
View File

@ -198,8 +198,7 @@ func walkBytesRunesToString(n *ir.ConvExpr, init *ir.Nodes) ir.Node {
a := typecheck.NodNil()
if n.Esc() == ir.EscNone {
// Create temporary buffer for string on stack.
t := types.NewArray(types.Types[types.TUINT8], tmpstringbufsize)
a = typecheck.NodAddr(typecheck.Temp(t))
a = stackBufAddr(tmpstringbufsize, types.Types[types.TUINT8])
}
if n.Op() == ir.ORUNES2STR {
// slicerunetostring(*[32]byte, []rune) string
@ -229,8 +228,7 @@ func walkBytesToStringTemp(n *ir.ConvExpr, init *ir.Nodes) ir.Node {
func walkRuneToString(n *ir.ConvExpr, init *ir.Nodes) ir.Node {
a := typecheck.NodNil()
if n.Esc() == ir.EscNone {
t := types.NewArray(types.Types[types.TUINT8], 4)
a = typecheck.NodAddr(typecheck.Temp(t))
a = stackBufAddr(4, types.Types[types.TUINT8])
}
// intstring(*[4]byte, rune)
return mkcall("intstring", n.Type(), init, a, typecheck.Conv(n.X, types.Types[types.TINT64]))
@ -246,7 +244,7 @@ func walkStringToBytes(n *ir.ConvExpr, init *ir.Nodes) ir.Node {
t := types.NewArray(types.Types[types.TUINT8], int64(len(sc)))
var a ir.Node
if n.Esc() == ir.EscNone && len(sc) <= int(ir.MaxImplicitStackVarSize) {
a = typecheck.NodAddr(typecheck.Temp(t))
a = stackBufAddr(t.NumElem(), t.Elem())
} else {
types.CalcSize(t)
a = ir.NewUnaryExpr(base.Pos, ir.ONEW, nil)
@ -273,8 +271,7 @@ func walkStringToBytes(n *ir.ConvExpr, init *ir.Nodes) ir.Node {
a := typecheck.NodNil()
if n.Esc() == ir.EscNone {
// Create temporary buffer for slice on stack.
t := types.NewArray(types.Types[types.TUINT8], tmpstringbufsize)
a = typecheck.NodAddr(typecheck.Temp(t))
a = stackBufAddr(tmpstringbufsize, types.Types[types.TUINT8])
}
// stringtoslicebyte(*32[byte], string) []byte
return mkcall("stringtoslicebyte", n.Type(), init, a, typecheck.Conv(s, types.Types[types.TSTRING]))
@ -298,8 +295,7 @@ func walkStringToRunes(n *ir.ConvExpr, init *ir.Nodes) ir.Node {
a := typecheck.NodNil()
if n.Esc() == ir.EscNone {
// Create temporary buffer for slice on stack.
t := types.NewArray(types.Types[types.TINT32], tmpstringbufsize)
a = typecheck.NodAddr(typecheck.Temp(t))
a = stackBufAddr(tmpstringbufsize, types.Types[types.TINT32])
}
// stringtoslicerune(*[32]rune, string) []rune
return mkcall("stringtoslicerune", n.Type(), init, a, typecheck.Conv(n.X, types.Types[types.TSTRING]))

3
src/cmd/compile/internal/walk/expr.go
View File

@ -441,8 +441,7 @@ func walkAddString(n *ir.AddStringExpr, init *ir.Nodes) ir.Node {
// Don't allocate the buffer if the result won't fit.
if sz < tmpstringbufsize {
// Create temporary buffer for result string on stack.
t := types.NewArray(types.Types[types.TUINT8], tmpstringbufsize)
buf = typecheck.NodAddr(typecheck.Temp(t))
buf = stackBufAddr(tmpstringbufsize, types.Types[types.TUINT8])
}
}

47
src/cmd/compile/internal/walk/temp.go Normal file
View File

@ -0,0 +1,47 @@
// Copyright 2021 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 walk
import (
"cmd/compile/internal/base"
"cmd/compile/internal/ir"
"cmd/compile/internal/typecheck"
"cmd/compile/internal/types"
)
// initStackTemp appends statements to init to initialize the given
// temporary variable, and then returns the expression &tmp. If vardef
// is true, then the variable is initialized with OVARDEF, and the
// caller must ensure the variable is later assigned before use;
// otherwise, it's zero initialized.
//
// TODO(mdempsky): Change callers to provide tmp's initial value,
// rather than just vardef, to make this safer/easier to use.
func initStackTemp(init *ir.Nodes, tmp *ir.Name, vardef bool) *ir.AddrExpr {
if vardef {
init.Append(ir.NewUnaryExpr(base.Pos, ir.OVARDEF, tmp))
} else {
appendWalkStmt(init, ir.NewAssignStmt(base.Pos, tmp, nil))
}
return typecheck.Expr(typecheck.NodAddr(tmp)).(*ir.AddrExpr)
}
// stackTempAddr returns the expression &tmp, where tmp is a newly
// allocated temporary variable of the given type. Statements to
// zero-initialize tmp are appended to init.
func stackTempAddr(init *ir.Nodes, typ *types.Type) *ir.AddrExpr {
return initStackTemp(init, typecheck.Temp(typ), false)
}
// stackBufAddr returns thte expression &tmp, where tmp is a newly
// allocated temporary variable of type [len]elem. This variable is
// initialized, and elem must not contain pointers.
func stackBufAddr(len int64, elem *types.Type) *ir.AddrExpr {
if elem.HasPointers() {
base.FatalfAt(base.Pos, "%v has pointers", elem)
}
tmp := typecheck.Temp(types.NewArray(elem, len))
return typecheck.Expr(typecheck.NodAddr(tmp)).(*ir.AddrExpr)
}