[llvm] [AMDGPU][AMDGPULateCodeGenPrepare] Combine scalarized selects back into vector selects (PR #173990)

[Pankaj Dwivedi via llvm-commits]

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@@ -225,6 +253,20 @@ bool AMDGPULateCodeGenPrepare::run() {
       Changed |= LRO.optimizeLiveType(&I, DeadInsts);
     }
 
+  // Combine scalarized selects back into vector selects.
+  // This uses a top-down approach: iterate over bitcasts (i32 vec -> i8 vec)
+  // and collect all select instructions that use extracted elements with a
+  // zero false value. By starting from the bitcast, we process each source
+  // exactly once, avoiding redundant work when multiple selects share a source.
+  if (CombineScalarSelects) {
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PankajDwivedi-25 wrote:

addressed.

https://github.com/llvm/llvm-project/pull/173990