[llvm-branch-commits] [DirectX] Lower `@llvm.dx.handle.fromBinding` to DXIL ops (PR #104251)

[David Peixotto via llvm-branch-commits]

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@@ -119,6 +123,119 @@ class OpLowerer {
     });
   }
 
+  Value *createTmpHandleCast(Value *V, Type *Ty) {
+    Function *CastFn = Intrinsic::getDeclaration(&M, Intrinsic::dx_cast_handle,
+                                                 {Ty, V->getType()});
+    CallInst *Cast = OpBuilder.getIRB().CreateCall(CastFn, {V});
+    CleanupCasts.push_back(Cast);
+    return Cast;
+  }
+
+  void cleanupHandleCasts() {
+    SmallVector<CallInst *> ToRemove;
+    SmallVector<Function *> CastFns;
+
+    for (CallInst *Cast : CleanupCasts) {
+      CastFns.push_back(Cast->getCalledFunction());
+      // All of the ops should be using `dx.types.Handle` at this point, so if
+      // we're not producing that we should be part of a pair. Track this so we
+      // can remove it at the end.
+      if (Cast->getType() != OpBuilder.getHandleType()) {
+        ToRemove.push_back(Cast);
+        continue;
+      }
+      // Otherwise, we're the second handle in a pair. Forward the arguments and
+      // remove the (second) cast.
+      CallInst *Def = cast<CallInst>(Cast->getOperand(0));
+      assert(Def->getIntrinsicID() == Intrinsic::dx_cast_handle &&
+             "Unbalanced pair of temporary handle casts");
+      Cast->replaceAllUsesWith(Def->getOperand(0));
+      Cast->eraseFromParent();
+    }
+    for (CallInst *Cast : ToRemove) {
+      assert(Cast->user_empty() && "Temporary handle cast still has users");
+      Cast->eraseFromParent();
+    }
+    llvm::sort(CastFns);
+    CastFns.erase(llvm::unique(CastFns), CastFns.end());
+    for (Function *F : CastFns)
+      F->eraseFromParent();
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dmpots wrote:

The explanation is good, can we get that added as a comment?

https://github.com/llvm/llvm-project/pull/104251