[llvm] [NVPTX] Add intrinsics for the szext instruction (PR #139126)

[Alex MacLean via llvm-commits]

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@@ -568,6 +568,99 @@ to left-shift the found bit into the most-significant bit position, otherwise
 the result is the shift amount needed to right-shift the found bit into the
 least-significant bit position. 0xffffffff is returned if no 1 bit is found.
 
+'``llvm.nvvm.zext.inreg.clamp``' Intrinsic
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AlexMaclean wrote:

I'll remove it. The intent was to match the convention of the `ISD::SEXT_INREG` node which performs an operation similar to this if `%b` were a constant. 

https://github.com/llvm/llvm-project/pull/139126