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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/runtime | |
| 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/runtime')
| -rw-r--r-- | src/runtime/stack.go | 9 |
1 files changed, 4 insertions, 5 deletions
diff --git a/src/runtime/stack.go b/src/runtime/stack.go index 55e97e77af..c92accf188 100644 --- a/src/runtime/stack.go +++ b/src/runtime/stack.go @@ -12,6 +12,7 @@ import ( "internal/runtime/atomic" "internal/runtime/gc" "internal/runtime/sys" + "math/bits" "unsafe" ) @@ -181,12 +182,10 @@ func stackinit() { // stacklog2 returns ⌊log_2(n)⌋. func stacklog2(n uintptr) int { - log2 := 0 - for n > 1 { - n >>= 1 - log2++ + if n == 0 { + return 0 } - return log2 + return bits.Len64(uint64(n)) } // Allocates a stack from the free pool. Must be called with |