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cmd/compile: slightly optimize adding 128

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'SUBQ $-0x80, r' is shorter to encode than 'ADDQ $0x80, r',
and functionally equivalent. Use it instead.

Shaves off a few bytes here and there:

file    before    after     Δ       %       
compile 25935856  25927664  -8192   -0.032% 
nm      4251840   4247744   -4096   -0.096% 

Change-Id: Ia9e02ea38cbded6a52a613b92e3a914f878d931e
Reviewed-on: https://go-review.googlesource.com/c/go/+/168344
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
This commit is contained in:
Josh Bleecher Snyder 2019-03-19 12:26:22 -07:00
parent fc1e6915dc
commit 250b96a7bf
2 changed files with 27 additions and 3 deletions
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10
test/codegen/arithmetic.go
View file

@ -381,3 +381,13 @@ func MULS(a, b, c uint32) (uint32, uint32, uint32) {
r2 := c - b*64
return r0, r1, r2
}
func addSpecial(a, b, c uint32) (uint32, uint32, uint32) {
// amd64:`INCL`
a++
// amd64:`DECL`
b--
// amd64:`SUBL.*-128`
c += 128
return a, b, c
}