| commit | 0a2f7757e38b07c2e40c5c885a7100e8c16eb40f | [log] [tgz] |
|---|---|---|
| author | Protobuf Team Bot <protobuf-github-bot@google.com> | Thu Dec 14 18:54:05 2023 -0800 |
| committer | Copybara-Service <copybara-worker@google.com> | Thu Dec 14 18:59:03 2023 -0800 |
| tree | c15e08b815750706ec6bfbf6938a4107d56d28b7 | |
| parent | eea39d6f53b2e9ae9432c038d3754fcc00ba9228 [diff] |
Branch-free varint size calculation. On android art, compiles to:
```
int com.google.android.test.Outer.computeUInt32SizeNoTag(int) [24 bytes]
0x000024d0 mov w0, #0x160
0x000024d4 clz w1, w1
0x000024d8 add w1, w1, w1, lsl #3
0x000024dc sub w0, w0, w1
0x000024e0 lsr w0, w0, #6
0x000024e4 ret
```
versus existing:
```
int com.google.android.test.Outer.computeUInt32SizeNoTag(int) [72 bytes]
0x000022a0 and w0, w1, #0xffffff80
0x000022a4 cbnz w0, #+0xc (addr 0x22b0)
0x000022a8 mov w0, #0x1
0x000022ac b #+0x38 (addr 0x22e4)
0x000022b0 and w0, w1, #0xffffc000
0x000022b4 cbnz w0, #+0xc (addr 0x22c0)
0x000022b8 mov w0, #0x2
0x000022bc b #+0x28 (addr 0x22e4)
0x000022c0 and w0, w1, #0xffe00000
0x000022c4 cbnz w0, #+0xc (addr 0x22d0)
0x000022c8 mov w0, #0x3
0x000022cc b #+0x18 (addr 0x22e4)
0x000022d0 mov w2, #0x5
0x000022d4 mov w0, #0x4
0x000022d8 and w1, w1, #0xf0000000
0x000022dc cmp w1, #0x0 (0)
0x000022e0 csel w0, w2, w0, ne
0x000022e4 ret
```
PiperOrigin-RevId: 591113652
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