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| author | Axel Wagner <axel.wagner.hh@googlemail.com> | 2025-11-19 09:28:16 +0100 |
|---|---|---|
| committer | Sean Liao <sean@liao.dev> | 2025-11-23 03:49:34 -0800 |
| commit | a18294bb6aa8f0dd656f2bcb6742f9de2936d0dc (patch) | |
| tree | 7d9c0dfc5cfbfe4968c6edfaf6b955e06cbb12e9 /src/cmd/internal | |
| parent | 437323ef7b933255c5c7fbb0775019e95f19b05e (diff) | |
| download | go-a18294bb6aa8f0dd656f2bcb6742f9de2936d0dc.tar.xz | |
cmd/internal/obj/arm64, image/gif, runtime, sort: use math/bits to calculate log2
In several places the integer log2 is calculated using loops or similar
mechanisms. math/bits.Len* provide a simpler and more efficient
mechanisms for this.
Annoyingly, every usage has slightly different ideas of what "log2"
means and how non-positive inputs should be handled. I verified the
replacements in each case by comparing the result for inputs from 0
to 1<<16.
Change-Id: Ie962a74674802da363e0038d34c06979ccb41cf3
Reviewed-on: https://go-review.googlesource.com/c/go/+/721880
Reviewed-by: Mark Freeman <markfreeman@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Diffstat (limited to 'src/cmd/internal')
| -rw-r--r-- | src/cmd/internal/obj/arm64/asm7.go | 27 |
1 files changed, 1 insertions, 26 deletions
diff --git a/src/cmd/internal/obj/arm64/asm7.go b/src/cmd/internal/obj/arm64/asm7.go index ccf8eda495..7addf0ddad 100644 --- a/src/cmd/internal/obj/arm64/asm7.go +++ b/src/cmd/internal/obj/arm64/asm7.go @@ -1674,32 +1674,7 @@ func log2(x uint64) uint32 { if x == 0 { panic("log2 of 0") } - n := uint32(0) - if x >= 1<<32 { - x >>= 32 - n += 32 - } - if x >= 1<<16 { - x >>= 16 - n += 16 - } - if x >= 1<<8 { - x >>= 8 - n += 8 - } - if x >= 1<<4 { - x >>= 4 - n += 4 - } - if x >= 1<<2 { - x >>= 2 - n += 2 - } - if x >= 1<<1 { - x >>= 1 - n += 1 - } - return n + return uint32(bits.Len64(x) - 1) } func autoclass(l int64) int { |