[clang] [HLSL] Implement support for HLSL intrinsic - select (PR #107129)

[Cooper Partin via cfe-commits]

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@@ -18695,6 +18695,50 @@ case Builtin::BI__builtin_hlsl_elementwise_isinf: {
         CGM.getHLSLRuntime().getSaturateIntrinsic(), ArrayRef<Value *>{Op0},
         nullptr, "hlsl.saturate");
   }
+  case Builtin::BI__builtin_hlsl_select: {
+    Value *OpCond = EmitScalarExpr(E->getArg(0));
+    Value *OpTrue = EmitScalarExpr(E->getArg(1));
+    Value *OpFalse = EmitScalarExpr(E->getArg(2));
+    llvm::Type *TCond = OpCond->getType();
+
+    // if cond is a bool emit a select instruction
+    if (TCond->isIntegerTy(1))
+      return Builder.CreateSelect(OpCond, OpTrue, OpFalse, "hlsl.select");
+
+    // if cond is a vector of bools lower to a shufflevector
+    // todo check if that true and false are vectors
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coopp wrote:

Very cool.. I do the same.

https://github.com/llvm/llvm-project/pull/107129