[clang] [HLSL] Use ExtVector for firstbit intrinsics (PR #142679)

[Sarah Spall via cfe-commits]

spall wrote:

I don't fully understand why this was a problem? Can you reshare the original crash you saw, not the minimized godbolt example?
This for example uses getVectorType https://github.com/llvm/llvm-project/blob/97686f2cd074a143022397b94ab1af1784ed75f2/clang/lib/Sema/SemaHLSL.cpp#L2170
Should we change it there as well? 

https://github.com/llvm/llvm-project/pull/142679