[clang] [MSVC, ARM64] Add _Copy* and _Count* intrinsics (PR #66554)

[Amy Huang via cfe-commits]

================
@@ -10779,6 +10779,70 @@ Value *CodeGenFunction::EmitAArch64BuiltinExpr(unsigned BuiltinID,
     return Load;
   }
 
+  if (BuiltinID == AArch64::BI_CopyDoubleFromInt64 ||
+      BuiltinID == AArch64::BI_CopyFloatFromInt32 ||
+      BuiltinID == AArch64::BI_CopyInt32FromFloat ||
+      BuiltinID == AArch64::BI_CopyInt64FromDouble) {
+    Value *Arg = EmitScalarExpr(E->getArg(0));
+    llvm::Type *RetTy = ConvertType(E->getType());
+    return Builder.CreateBitCast(Arg, RetTy);
+  }
+
+  if (BuiltinID == AArch64::BI_CountLeadingOnes ||
+      BuiltinID == AArch64::BI_CountLeadingOnes64 ||
+      BuiltinID == AArch64::BI_CountLeadingZeros ||
+      BuiltinID == AArch64::BI_CountLeadingZeros64) {
+    Value *Arg = EmitScalarExpr(E->getArg(0));
+    llvm::Type *ArgType = Arg->getType();
+
+    if (BuiltinID == AArch64::BI_CountLeadingOnes ||
+        BuiltinID == AArch64::BI_CountLeadingOnes64)
+      Arg = Builder.CreateXor(Arg, Constant::getAllOnesValue(ArgType));
+
+    Function *F = CGM.getIntrinsic(Intrinsic::ctlz, ArgType);
+    Value *Result = Builder.CreateCall(F, {Arg, Builder.getInt1(false)});
+
+    if (BuiltinID == AArch64::BI_CountLeadingOnes64 ||
+        BuiltinID == AArch64::BI_CountLeadingZeros64)
+      Result = Builder.CreateTrunc(Result, Builder.getInt32Ty());
+    return Result;
+  }
+
+  if (BuiltinID == AArch64::BI_CountLeadingSigns ||
+      BuiltinID == AArch64::BI_CountLeadingSigns64) {
+    Value *Arg = EmitScalarExpr(E->getArg(0));
+    llvm::Type *ArgType = Arg->getType();
+
+    Function *F;
+    if (BuiltinID == AArch64::BI_CountLeadingSigns) {
+      F = CGM.getIntrinsic(Intrinsic::aarch64_cls);
+      if (ArgType != Builder.getInt32Ty())
----------------
amykhuang wrote:

Yeah, I'm a bit confused by this. It was coming up in the test case when building with `-triple arm64-darwin`.  It seemed everything was being converted to int64 at the beginning of the function? 

https://github.com/llvm/llvm-project/pull/66554