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6b8e3e2d06
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>
23 lines
494 B
Go
23 lines
494 B
Go
// asmcheck
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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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package codegen
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//go:registerparams
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func f1(a, b int) {
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// amd64:"MOVQ\tBX, CX", "MOVQ\tAX, BX", "MOVL\t\\$1, AX", -"MOVQ\t.*DX"
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g(1, a, b)
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}
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//go:registerparams
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func f2(a, b int) {
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// amd64:"MOVQ\tBX, AX", "MOVQ\t[AB]X, CX", -"MOVQ\t.*, BX"
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g(b, b, b)
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}
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//go:noinline
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//go:registerparams
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func g(int, int, int) {}
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