[clang] [llvm] Adding splitdouble HLSL function (PR #109331)

[Farzon Lotfi via cfe-commits]

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@@ -95,6 +99,125 @@ static void initializeAlloca(CodeGenFunction &CGF, AllocaInst *AI, Value *Size,
   I->addAnnotationMetadata("auto-init");
 }
 
+static Value *handleHlslSplitdouble(const CallExpr *E, CodeGenFunction *CGF) {
+  Value *Op0 = CGF->EmitScalarExpr(E->getArg(0));
+  const auto *OutArg1 = dyn_cast<HLSLOutArgExpr>(E->getArg(1));
+  const auto *OutArg2 = dyn_cast<HLSLOutArgExpr>(E->getArg(2));
+
+  CallArgList Args;
+  LValue Op1TmpLValue =
+      CGF->EmitHLSLOutArgExpr(OutArg1, Args, OutArg1->getType());
+  LValue Op2TmpLValue =
+      CGF->EmitHLSLOutArgExpr(OutArg2, Args, OutArg2->getType());
+
+  if (CGF->getTarget().getCXXABI().areArgsDestroyedLeftToRightInCallee())
+    Args.reverseWritebacks();
+
+  Value *LowBits = nullptr;
+  Value *HighBits = nullptr;
+
+  if (CGF->CGM.getTarget().getTriple().isDXIL()) {
+
+    llvm::Type *RetElementTy = CGF->Int32Ty;
+    if (auto *Op0VecTy = E->getArg(0)->getType()->getAs<clang::VectorType>())
+      RetElementTy = llvm::VectorType::get(
+          CGF->Int32Ty, ElementCount::getFixed(Op0VecTy->getNumElements()));
+    auto *RetTy = llvm::StructType::get(RetElementTy, RetElementTy);
+
+    CallInst *CI = CGF->Builder.CreateIntrinsic(
+        RetTy, Intrinsic::dx_splitdouble, {Op0}, nullptr, "hlsl.splitdouble");
+
+    LowBits = CGF->Builder.CreateExtractValue(CI, 0);
+    HighBits = CGF->Builder.CreateExtractValue(CI, 1);
+
+  } else {
+    // For Non DXIL targets we generate the instructions.
+    // TODO: This code accounts for known limitations in
+    // SPIR-V and splitdouble. Such should be handled,
+    // in a later compilation stage. After [issue link here]
----------------
farzonl wrote:

Please add the issue you are refrencing.

https://github.com/llvm/llvm-project/pull/109331