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cmd/compile: avoid generating duplicated in-register Arg
In expand_calls, when rewriting OpArg to OpArgIntReg/OpArgFloatReg, avoid generating duplicates. Otherwise it will confuse the register allocator: it would think the second occurance clobbers the first's register, causing it to generate copies, which may clobber other args. Change-Id: I4f1dc0519afb77500eae1c0e6ac8745e51f7aa4e Reviewed-on: https://go-review.googlesource.com/c/go/+/306029 Trust: Cherry Zhang <cherryyz@google.com> Reviewed-by: Than McIntosh <thanm@google.com> Reviewed-by: David Chase <drchase@google.com>
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@ -1378,6 +1378,11 @@ func expandCalls(f *Func) {
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// rewriteArgToMemOrRegs converts OpArg v in-place into the register version of v,
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// if that is appropriate.
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func (x *expandState) rewriteArgToMemOrRegs(v *Value) *Value {
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if x.debug {
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x.indent(3)
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defer x.indent(-3)
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x.Printf("rewriteArgToMemOrRegs(%s)\n", v.LongString())
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}
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pa := x.prAssignForArg(v)
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switch len(pa.Registers) {
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case 0:
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@ -1387,15 +1392,26 @@ func (x *expandState) rewriteArgToMemOrRegs(v *Value) *Value {
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pa.Offset(), frameOff, v.LongString()))
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}
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case 1:
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t := v.Type
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key := selKey{v, 0, t.Width, t}
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w := x.commonArgs[key]
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if w != nil {
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v.copyOf(w)
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break
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}
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r := pa.Registers[0]
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var i int64
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v.Op, i = ArgOpAndRegisterFor(r, x.f.ABISelf)
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v.Aux = &AuxNameOffset{v.Aux.(*ir.Name), 0}
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v.AuxInt = i
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x.commonArgs[key] = v
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default:
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panic(badVal("Saw unexpanded OpArg", v))
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}
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if x.debug {
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x.Printf("-->%s\n", v.LongString())
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}
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return v
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}
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29
test/abi/store_reg_args.go
Normal file
29
test/abi/store_reg_args.go
Normal file
@ -0,0 +1,29 @@
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// run
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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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// When the function Store an Arg and also use it in another place,
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// be sure not to generate duplicated OpArgXXXReg values, which confuses
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// the register allocator.
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package main
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//go:noinline
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//go:registerparams
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func F(x, y float32) {
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if x < 0 {
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panic("FAIL")
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}
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g = [4]float32{x, y, x, y}
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}
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var g [4]float32
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func main() {
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F(1, 2)
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if g[0] != 1 || g[1] != 2 || g[2] != 1 || g[3] != 2 {
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panic("FAIL")
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}
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}
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