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

[Farzon Lotfi via cfe-commits]

================
@@ -18901,6 +18901,160 @@ case Builtin::BI__builtin_hlsl_elementwise_isinf: {
         CGM.getHLSLRuntime().getRadiansIntrinsic(), ArrayRef<Value *>{Op0},
         nullptr, "hlsl.radians");
   }
+  // This should only be called when targeting DXIL
+  case Builtin::BI__builtin_hlsl_splitdouble: {
+
+    assert((E->getArg(0)->getType()->hasFloatingRepresentation() &&
+            E->getArg(1)->getType()->hasUnsignedIntegerRepresentation() &&
+            E->getArg(2)->getType()->hasUnsignedIntegerRepresentation()) &&
+           "asuint operands types mismatch");
+    Value *Op0 = EmitScalarExpr(E->getArg(0));
+    const auto *OutArg1 = dyn_cast<HLSLOutArgExpr>(E->getArg(1));
+    const auto *OutArg2 = dyn_cast<HLSLOutArgExpr>(E->getArg(2));
+
+    CallArgList Args;
+    auto [Op1BaseLValue, Op1TmpLValue] =
+        EmitHLSLOutArgExpr(OutArg1, Args, OutArg1->getType());
+    auto [Op2BaseLValue, Op2TmpLValue] =
+        EmitHLSLOutArgExpr(OutArg2, Args, OutArg2->getType());
+
+    if (CGM.getTarget().getTriple().isDXIL()) {
+
+      llvm::StructType *RetType = nullptr;
+
+      if (Op0->getType()->isVectorTy()) {
+        auto *Op0VecTy = E->getArg(0)->getType()->getAs<VectorType>();
+
+        llvm::VectorType *i32VecTy = llvm::VectorType::get(
+            Int32Ty, ElementCount::getFixed(Op0VecTy->getNumElements()));
+        RetType = llvm::StructType::get(i32VecTy, i32VecTy);
+      } else {
+        RetType = llvm::StructType::get(Int32Ty, Int32Ty);
+      }
+
+      CallInst *CI =
+          Builder.CreateIntrinsic(RetType, Intrinsic::dx_splitdouble, {Op0},
+                                  nullptr, "hlsl.splitdouble");
+
+      Value *Arg0 = Builder.CreateExtractValue(CI, 0);
+      Value *Arg1 = Builder.CreateExtractValue(CI, 1);
+
+      Builder.CreateStore(Arg0, Op1TmpLValue.getAddress());
+      auto *s = Builder.CreateStore(Arg1, Op2TmpLValue.getAddress());
+
+      EmitWritebacks(*this, Args);
+      return s;
+    }
+
+    assert(!CGM.getTarget().getTriple().isDXIL() &&
+           "For non-DXIL targets we generate the instructions");
+
+    if (!Op0->getType()->isVectorTy()) {
+      FixedVectorType *DestTy = FixedVectorType::get(Int32Ty, 2);
+      Value *Bitcast = Builder.CreateBitCast(Op0, DestTy);
+
+      Value *Arg0 = Builder.CreateExtractElement(Bitcast, 0.0);
+      Value *Arg1 = Builder.CreateExtractElement(Bitcast, 1.0);
+
+      Builder.CreateStore(Arg0, Op1TmpLValue.getAddress());
+      auto *s = Builder.CreateStore(Arg1, Op2TmpLValue.getAddress());
+
+      EmitWritebacks(*this, Args);
+      return s;
+    }
+
+    auto emitVectorCode =
+        [](Value *Op, CGBuilderTy *Builder,
+           FixedVectorType *DestTy) -> std::pair<Value *, Value *> {
+      Value *bitcast = Builder->CreateBitCast(Op, DestTy);
+
+      SmallVector<int> LowbitsIndex;
+      SmallVector<int> HighbitsIndex;
+
+      for (unsigned int idx = 0; idx < DestTy->getNumElements(); idx += 2) {
----------------
farzonl wrote:

The clang style is for variables to be capital. so this would be `Idx`. The line above would be `EmitVectorCode`.

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