| commit | d556c251a1f1506f68e1e4064c3537948ff667a3 | [log] [tgz] |
|---|---|---|
| author | fanzha02 <fannie.zhang@arm.com> | Thu May 28 18:11:52 2020 +0800 |
| committer | Keith Randall <khr@golang.org> | Mon Aug 24 14:52:54 2020 +0000 |
| tree | de93499d86a24e3b777265f99122c161ce3ac768 | |
| parent | 4e4d5df0b0af23d2fcb5690e89f27bd7e64e48f1 [diff] |
cmd/compile: add more generic rewrite rules to reassociate (op (op y C) x|C)
With this patch, opt pass can expose more obvious constant-folding
opportunites.
Example:
func test(i int) int {return (i+8)-(i+4)}
The previous version:
MOVD "".i(FP), R0
ADD $8, R0, R1
ADD $4, R0, R0
SUB R0, R1, R0
MOVD R0, "".~r1+8(FP)
RET (R30)
The optimized version:
MOVD $4, R0
MOVD R0, "".~r1+8(FP)
RET (R30)
This patch removes some existing reassociation rules, such as "x+(z-C)",
because the current generic rewrite rules will canonicalize "x-const"
to "x+(-const)", making "x+(z-C)" equal to "x+(z+(-C))".
This patch also adds test cases.
Change-Id: I857108ba0b5fcc18a879eeab38e2551bc4277797
Reviewed-on: https://go-review.googlesource.com/c/go/+/237137
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
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