[llvm] [ADT] Out-of-line the trivially-copyable SmallVector::push_back grow path (PR #206213)

[Fangrui Song via llvm-commits]

MaskRay wrote:


Significant (≥3σ vs. measured noise): 🟢 improvement · 🔴 regression. Unmarked = within noise.

| Configuration | instructions:u | max-rss |
|---|---:|---:|
| stage1-O3 | 🟢 **-0.45%** | +0.16% |
| stage1-ReleaseThinLTO | 🟢 **-0.43%** | +0.06% |
| stage1-ReleaseLTO-g | 🟢 **-0.47%** | 🔴 **+0.21%** |
| stage1-O0-g | 🟢 **-0.45%** | -0.10% |
| stage1-aarch64-O3 | 🟢 **-0.41%** | +0.01% |
| stage1-aarch64-O0-g | 🟢 **-0.47%** | 🟢 **-0.46%** |
| stage2-O3 | 🟢 **-0.49%** | 🔴 **+0.44%** |
| stage2-O0-g | 🟢 **-0.51%** | 🔴 **+0.42%** |

Clang build:

| Metric | Old | New | Δ |
|---|---:|---:|---:|
| instructions:u | 20047256M | 19939658M | 🟢 **-0.54%** |
| wall-time | 336.54s | 335.76s | -0.23% |
| size-file | 137770KiB | 137950KiB | 🔴 **+0.13%** |
| size-file (stage1) | 154311KiB | 154327KiB | 🔴 **+0.01%** |

https://github.com/llvm/llvm-project/pull/206213