Reland "[Transforms] LoopIdiomRecognize recognize strlen and wcslen (#108985)" (#131412)

Relands https://github.com/llvm/llvm-project/pull/108985

This PR continues the effort made in
https://discourse.llvm.org/t/rfc-strlen-loop-idiom-recognition-folding/55848
and https://reviews.llvm.org/D83392 and https://reviews.llvm.org/D88460
to extend `LoopIdiomRecognize` to find and replace loops of the form
```c
base = str;
while (*str)
  ++str;
```
and transforming the `strlen` loop idiom into the appropriate `strlen`
and `wcslen` library call which will give a small performance boost if
replaced.
```c
str = base + strlen(base)
len = str - base
```

0 files changed, 0 insertions, 0 deletions