[llvm] [DXIL] Add sign intrinsic part 2 (PR #101988)

[Tim Gymnich via llvm-commits]

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@@ -293,6 +295,36 @@ static bool expandClampIntrinsic(CallInst *Orig, Intrinsic::ID ClampIntrinsic) {
   return true;
 }
 
+static bool expandSignIntrinsic(CallInst *Orig) {
+  IRBuilder<> Builder(Orig->getParent());
+  Value *X = Orig->getOperand(0);
+  Type *Ty = X->getType();
+  Type *ScalarTy = Ty->getScalarType();
+  Type *RetTy = Orig->getType();
+  Constant *Zero = Constant::getNullValue(Ty);
+  Builder.SetInsertPoint(Orig);
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tgymnich wrote:

We can either add `usign` builtins/intrinsics all the way down from hlsl to dxil and spirv. Or just add a high level builtin to hlsl. 

I don't like the idea of having an intrinsic for `select(x == 0, 0, 1)`.
I wonder from a consistency point of view if it is even necessary to have a `usign` builtin since `abs` also only seems to offer the signed variants in `hlsl_intrinsics.h`.

https://github.com/llvm/llvm-project/pull/101988