[llvm] [ADT] ImutAVLFactory: avoid overhead of vector for freelist (PR #196534)

[Christoph Cullmann via llvm-commits]

christoph-cullmann wrote:

I did now run my test case again, with and without this patch:

Before:

```
command: /local/ssd/cullmann/build/isa.default/usr/bin/clang-tidy -p . -config-file=/local/ssd/cullmann/build/isa.default/usr/build/common/clang-tidy.yaml /local/ssd/cullmann/build/isa.default/isa/target/arm/decoder/arm.cpp
user:  53.95(5395) system:   2.97(297)
elapsed:  57.15
MAXSIZE: 10833.137M(2773283), MAXRSS: 10250.625M(2624160)
AVGSIZE: 5998.184M(1535535), AVGRSS: 5918.305M(1515086)
```

Now:

```
command: /local/ssd/cullmann/build/llvm-usr/bin/clang-tidy -p . -config-file=/local/ssd/cullmann/build/isa.default/usr/build/common/clang-tidy.yaml /local/ssd/cullmann/build/isa.default/isa/target/arm/decoder/arm.cpp
user:  51.55(5155) system:   2.58(258)
elapsed:  54.34
MAXSIZE: 9546.668M(2443947), MAXRSS: 9468.184M(2423855)
AVGSIZE: 5918.301M(1515085), AVGRSS: 5852.762M(1498307)
```

I will try a version with std::vector, later, too, just to be sure.


https://github.com/llvm/llvm-project/pull/196534