| commit | 929905bd2825b9e6d961e39647d0aaa9376e4a06 | [log] [tgz] |
|---|---|---|
| author | Protobuf Team Bot <protobuf-github-bot@google.com> | Thu Dec 05 12:46:00 2024 -0800 |
| committer | Copybara-Service <copybara-worker@google.com> | Thu Dec 05 12:59:52 2024 -0800 |
| tree | 61ec425433c4537643380d76fe55701d86984765 | |
| parent | 671ae8f754583f51d3b02c91f08874e3df90b990 [diff] |
Minor binary search optimization for field lookup slow path.
On a Cortex-A55 this resulted in a 28.30% reduction in CPU and wall time for the binary search path.
Loop body before:
```
.LBB0_2:
add w8, w12, #1
cmp w8, w11
b.gt .LBB0_6 // Predictable branch, ends the loop
.LBB0_3:
add w12, w8, w11
add w12, w12, w12, lsr #31
asr w12, w12, #1
smaddl x0, w12, w10, x9
ldr w13, [x0]
cmp w13, w1
b.lo .LBB0_2 // Unpredictable branch here! Will be hit 50/50 in prod
b.ls .LBB0_7 // Predictable branch - ends the loop
sub w11, w12, #1
cmp w8, w11
b.le .LBB0_3 // Predictable branch - continues the loop
```
Loop body after:
```
.LBB7_1:
cmp w9, w11
b.hi .LBB7_4 // Predictable branch - ends the loop
add w12, w9, w11
lsr w12, w12, #1
umaddl x0, w12, w8, x10
sub w14, w12, #1
ldr w13, [x0]
cmp w13, w1
csel w11, w14, w11, hs
csinc w9, w9, w12, hs
b.ne .LBB7_1 // Predictable branch - continues the loop
```
PiperOrigin-RevId: 703214356
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