[llvm] [SLP]Improve minbitwidth analysis. (PR #78976)

[Nikita Popov via llvm-commits]

nikic wrote:

Seems to break the build, maybe on GCC only?
```

/var/llvm-compile-time-tracker/llvm-project/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp:3617:24: error: declaration of ‘llvm::TargetTransformInfo* llvm::slpvectorizer::BoUpSLP::TTI’ changes meaning of ‘TTI’ [-fpermissive]
 3617 |   TargetTransformInfo *TTI;
      |                        ^~~
In file included from /var/llvm-compile-time-tracker/llvm-project/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp:48:
/var/llvm-compile-time-tracker/llvm-project/llvm/include/llvm/Analysis/TargetTransformInfo.h:206:29: note: ‘TTI’ declared here as ‘typedef class llvm::TargetTransformInfo llvm::TTI’
  206 | typedef TargetTransformInfo TTI;
      |                             ^~~
```

https://github.com/llvm/llvm-project/pull/78976