[llvm] [IR] Add llvm `clmul` intrinsic (PR #140301)

[Matt Arsenault via llvm-commits]

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@@ -199,6 +199,25 @@ static Value *LowerCTLZ(LLVMContext &Context, Value *V, Instruction *IP) {
   return LowerCTPOP(Context, V, IP);
 }
 
+/// Emit the code to lower clmul of V1, V2 before the specified instruction IP.
+static Value *LowerCLMUL(LLVMContext &Context, Value *V1, Value *V2, Instruction *IP) {
+
+  IRBuilder<> Builder(IP);
+
+  unsigned BitSize = V1->getType()->getPrimitiveSizeInBits();
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arsenm wrote:

I'm assuming this doesn't work correctly with vectors? 

https://github.com/llvm/llvm-project/pull/140301