[llvm] [DXIL] Implement log intrinsic Lowering (PR #86569)

[Xiang Li via llvm-commits]

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@@ -169,6 +171,32 @@ static bool expandLerpIntrinsic(CallInst *Orig) {
   return true;
 }
 
+static bool expandLogIntrinsic(CallInst *Orig,
+                               float LogConstVal = numbers::ln2f) {
+  Value *X = Orig->getOperand(0);
+  IRBuilder<> Builder(Orig->getParent());
+  Builder.SetInsertPoint(Orig);
+  Type *Ty = X->getType();
+  Type *EltTy = Ty->getScalarType();
+  Constant *Ln2Const =
+      Ty->isVectorTy() ? ConstantVector::getSplat(
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python3kgae wrote:

Need test for vector type.

https://github.com/llvm/llvm-project/pull/86569