[clang] [llvm] [AMDGPU] Enable atomic optimizer for 64 bit divergent values (PR #96473)

[Vikram Hegde via cfe-commits]

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@@ -228,10 +228,11 @@ void AMDGPUAtomicOptimizerImpl::visitAtomicRMWInst(AtomicRMWInst &I) {
 
   // If the value operand is divergent, each lane is contributing a different
   // value to the atomic calculation. We can only optimize divergent values if
-  // we have DPP available on our subtarget, and the atomic operation is 32
-  // bits.
+  // we have DPP available on our subtarget, and the atomic operation is either
+  // 32 or 64 bits.
   if (ValDivergent &&
-      (!ST->hasDPP() || DL->getTypeSizeInBits(I.getType()) != 32)) {
+      (!ST->hasDPP() || (DL->getTypeSizeInBits(I.getType()) != 32 &&
+      DL->getTypeSizeInBits(I.getType()) != 64))) {
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vikramRH wrote:

Done

https://github.com/llvm/llvm-project/pull/96473