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

[Matt Arsenault via cfe-commits]

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@@ -311,10 +312,11 @@ void AMDGPUAtomicOptimizerImpl::visitIntrinsicInst(IntrinsicInst &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 32 or
+  // 64 bits.
   if (ValDivergent &&
-      (!ST->hasDPP() || DL->getTypeSizeInBits(I.getType()) != 32)) {
+      (!ST->hasDPP() || (DL->getTypeSizeInBits(I.getType()) != 32 &&
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arsenm wrote:

Ditto 

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