[llvm] [DirectX] Remove lifetime intrinsics and run Dead Store Elimination (PR #152636)

[Deric C. via llvm-commits]

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@@ -78,6 +82,17 @@ static bool forwardHandleAccesses(Function &F, DominatorTree &DT) {
         case Intrinsic::dx_resource_handlefromimplicitbinding:
           processHandle(II, HandleMap);
           break;
+        // Note: Lifetime intrinsics do not show up as users of an Alloca.
+        // As a result we walk the whole function to find the lifetimes and
+        // store them so that we may delete the alloca matches
+        case Intrinsic::lifetime_start:
+        case Intrinsic::lifetime_end:
+          if (II->arg_size() >= 1) {
+            Value *Ptr = II->getArgOperand(0);
+            if (auto *Alloca = dyn_cast<AllocaInst>(Ptr->stripPointerCasts()))
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Icohedron wrote:

The `Ptr->stripPointerCasts()` is a no-op here. The pointer operand of a Lifetime intrinsic must either be an AllocaInst or a PoisonValue; it can't be anything else.

https://github.com/llvm/llvm-project/pull/152636