[llvm] [AMDGPU] Support preloading hidden kernel arguments (PR #98861)

[Austin Kerbow via llvm-commits]

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@@ -2533,6 +2534,23 @@ void SITargetLowering::allocatePreloadKernArgSGPRs(
       unsigned NumAllocSGPRs =
           alignTo(ArgLoc.getLocVT().getFixedSizeInBits(), 32) / 32;
 
+      // Add padding SPGR to fix alignment for hidden arguments.
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kerbowa wrote:

Globalisel isn't supported with kernarg preloading. I'll work on adding support after this lands with #96030 being the first pre-req, it's a larger change.

https://github.com/llvm/llvm-project/pull/98861