[clang] [llvm] Add cross builtins and cross HLSL function to DirectX and SPIR-V backend (PR #109180)

[Joshua Batista via cfe-commits]

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@@ -74,6 +75,42 @@ static Value *expandAbs(CallInst *Orig) {
                                  "dx.max");
 }
 
+static Value *expandCrossIntrinsic(CallInst *Orig) {
+
+  VectorType *VT = cast<VectorType>(Orig->getType());
+  if (cast<FixedVectorType>(VT)->getNumElements() != 3)
+    report_fatal_error(Twine("return vector must have exactly 3 elements"),
+                       /* gen_crash_diag=*/false);
+
+  Value *op0 = Orig->getOperand(0);
+  Value *op1 = Orig->getOperand(1);
+  IRBuilder<> Builder(Orig);
+
+  Value *op0_x = Builder.CreateExtractElement(op0, (uint64_t)0, "x0");
+  Value *op0_y = Builder.CreateExtractElement(op0, 1, "x1");
+  Value *op0_z = Builder.CreateExtractElement(op0, 2, "x2");
+
+  Value *op1_x = Builder.CreateExtractElement(op1, (uint64_t)0, "y0");
+  Value *op1_y = Builder.CreateExtractElement(op1, 1, "y1");
+  Value *op1_z = Builder.CreateExtractElement(op1, 2, "y2");
+
+  auto MulSub = [&](Value *x0, Value *y0, Value *x1, Value *y1) -> Value * {
+    Value *xy = Builder.CreateFMul(x0, y1);
+    Value *yx = Builder.CreateFMul(y0, x1);
+    return Builder.CreateFSub(xy, yx);
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bob80905 wrote:

I tried it out and turns out each variable was assigned a unique variable name, contrary to what I expected. So your comment has been incorporated.

https://github.com/llvm/llvm-project/pull/109180