[llvm] [AMDGPU][True16] Select _t16 D16 loads/stores for FLAT/GLOBAL/SCRATCH (PR #210191)

[Jay Foad via llvm-commits]

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@@ -263,6 +263,12 @@ void AMDGPUDAGToDAGISelLegacy::getAnalysisUsage(AnalysisUsage &AU) const {
 
 bool AMDGPUDAGToDAGISel::matchLoadD16FromBuildVector(SDNode *N) const {
   assert(Subtarget->d16PreservesUnusedBits());
+  // In true16 mode the two 16-bit halves of a packed vector live in
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jayfoad wrote:

Instead of this you could return early from PreprocessISelDAG like we do for !d16PreservesUnusedBits.

https://github.com/llvm/llvm-project/pull/210191