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| author | Josh Bleecher Snyder <josharian@gmail.com> | 2020-04-20 14:43:30 -0700 |
|---|---|---|
| committer | Josh Bleecher Snyder <josharian@gmail.com> | 2020-04-21 00:38:34 +0000 |
| commit | 50b11318febd74c26cc466cc4557347bcb53181a (patch) | |
| tree | 1af35a1788920f922e481f23317091051988db56 /test | |
| parent | 12665b9a067789004ca45cedcd3ebbbdc143f1d7 (diff) | |
| download | go-50b11318febd74c26cc466cc4557347bcb53181a.tar.gz go-50b11318febd74c26cc466cc4557347bcb53181a.zip | |
cmd/compile: use oneBit instead of isPowerOfTwo in bit optimization
This optimization works on any integer with exactly one bit set.
This is identical to being a power of two, except in the
most negative number. Use oneBit instead.
The rule now triggers in a few more places in std+cmd,
in packages encoding/asn1, crypto/elliptic, and
vendor/golang.org/x/crypto/cryptobyte.
This change obviates the need for CL 222479
by doing this optimization consistently in the compiler.
Change-Id: I983c6235290fdc634fda5e11b10f1f8ce041272f
Reviewed-on: https://go-review.googlesource.com/c/go/+/229124
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Diffstat (limited to 'test')
| -rw-r--r-- | test/codegen/bits.go | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/test/codegen/bits.go b/test/codegen/bits.go index 18f9daf7cf..0a5428b55a 100644 --- a/test/codegen/bits.go +++ b/test/codegen/bits.go @@ -278,6 +278,11 @@ func bitOpOnMem(a []uint32) { a[5] ^= 0x2000 } +func bitcheckMostNegative(b uint8) bool { + // amd64:"TESTB" + return b&0x80 == 0x80 +} + // Check AND masking on arm64 (Issue #19857) func and_mask_1(a uint64) uint64 { |