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go/test/codegen/regabi_regalloc.go

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cmd/compile: reduce redundant register moves for regabi calls Currently, if we have AX=a and BX=b, and we want to make a call F(1, a, b), to move arguments into the desired registers it emits MOVQ AX, CX MOVL $1, AX // AX=1 MOVQ BX, DX MOVQ CX, BX // BX=a MOVQ DX, CX // CX=b This has a few redundant moves. This is because we process inputs in order. First, allocate 1 to AX, which kicks out a (in AX) to CX (a free register at the moment). Then, allocate a to BX, which kicks out b (in BX) to DX. Finally, put b to CX. Notice that if we start with allocating CX=b, then BX=a, AX=1, we will not have redundant moves. This CL reduces redundant moves by allocating them in different order: First, for inpouts that are already in place, keep them there. Then allocate free registers. Then everything else. before after cmd/compile binary size 23703888 23609680 text size 8565899 8533291 (with regabiargs enabled.) Change-Id: I69e1bdf745f2c90bb791f6d7c45b37384af1e874 Reviewed-on: https://go-review.googlesource.com/c/go/+/311371 Trust: Cherry Zhang <cherryyz@google.com> Reviewed-by: David Chase <drchase@google.com> Reviewed-by: Than McIntosh <thanm@google.com>
2021-04-17 20:50:13 -06:00
// asmcheck
// 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 codegen
//go:registerparams
func f1(a, b int) {
// amd64:"MOVQ\tBX, CX", "MOVQ\tAX, BX", "MOVL\t\\$1, AX", -"MOVQ\t.*DX"
g(1, a, b)
}
//go:registerparams
func f2(a, b int) {
// amd64:"MOVQ\tBX, AX", "MOVQ\t[AB]X, CX", -"MOVQ\t.*, BX"
g(b, b, b)
}
//go:noinline
//go:registerparams
func g(int, int, int) {}
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