Commit c1050a8e authored by Iskander Sharipov's avatar Iskander Sharipov Committed by Brad Fitzpatrick

cmd/compile: don't generate newobject call for 0-sized types

Emit &runtime.zerobase instead of a call to newobject for
allocations of zero sized objects in walk.go.

Fixes #29446

Change-Id: I11b67981d55009726a17c2e582c12ce0c258682e
Reviewed-on: https://go-review.googlesource.com/c/155840
Run-TryBot: Iskander Sharipov <quasilyte@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: default avatarCherry Zhang <cherryyz@google.com>
Reviewed-by: default avatarKeith Randall <khr@golang.org>
parent 3a903736
......@@ -1940,6 +1940,16 @@ func callnew(t *types.Type) *Node {
yyerror("%v is go:notinheap; heap allocation disallowed", t)
}
dowidth(t)
if t.Size() == 0 {
// Return &runtime.zerobase if we know that the requested size is 0.
// This is what runtime.mallocgc would return.
z := newname(Runtimepkg.Lookup("zerobase"))
z.SetClass(PEXTERN)
z.Type = t
return typecheck(nod(OADDR, z, nil), ctxExpr)
}
fn := syslook("newobject")
fn = substArgTypes(fn, t)
v := mkcall1(fn, types.NewPtr(t), nil, typename(t))
......
// asmcheck
// Copyright 2018 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.
// These tests check that allocating a 0-size object does not
// introduce a call to runtime.newobject.
package codegen
func zeroAllocNew1() *struct{} {
// 386:-`CALL\truntime\.newobject`
// amd64:-`CALL\truntime\.newobject`
// arm:-`CALL\truntime\.newobject`
// arm64:-`CALL\truntime\.newobject`
return new(struct{})
}
func zeroAllocNew2() *[0]int {
// 386:-`CALL\truntime\.newobject`
// amd64:-`CALL\truntime\.newobject`
// arm:-`CALL\truntime\.newobject`
// arm64:-`CALL\truntime\.newobject`
return new([0]int)
}
func zeroAllocSliceLit() []int {
// 386:-`CALL\truntime\.newobject`
// amd64:-`CALL\truntime\.newobject`
// arm:-`CALL\truntime\.newobject`
// arm64:-`CALL\truntime\.newobject`
return []int{}
}
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