diff --git a/src/cmd/compile/internal/gc/walk.go b/src/cmd/compile/internal/gc/walk.go index 57bf8a1e0e..1d6321212e 100644 --- a/src/cmd/compile/internal/gc/walk.go +++ b/src/cmd/compile/internal/gc/walk.go @@ -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)) diff --git a/test/codegen/alloc.go b/test/codegen/alloc.go new file mode 100644 index 0000000000..31455fdabf --- /dev/null +++ b/test/codegen/alloc.go @@ -0,0 +1,34 @@ +// 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{} +}