1 files changed, 23 insertions, 0 deletions
diff --git a/clang/lib/CodeGen/CGBuiltin.cpp b/clang/lib/CodeGen/CGBuiltin.cpp
index d9b2a5fe16be..1a02965b223e 100644
--- a/clang/lib/CodeGen/CGBuiltin.cpp
+++ b/clang/lib/CodeGen/CGBuiltin.cpp
@@ -9732,6 +9732,29 @@ Value *CodeGenFunction::EmitAArch64BuiltinExpr(unsigned BuiltinID,
     return Builder.CreateCall(F);
   }
 
+  if (BuiltinID == AArch64::BI__mulh || BuiltinID == AArch64::BI__umulh) {
+    llvm::Type *ResType = ConvertType(E->getType());
+    llvm::Type *Int128Ty = llvm::IntegerType::get(getLLVMContext(), 128);
+
+    bool IsSigned = BuiltinID == AArch64::BI__mulh;
+    Value *LHS =
+        Builder.CreateIntCast(EmitScalarExpr(E->getArg(0)), Int128Ty, IsSigned);
+    Value *RHS =
+        Builder.CreateIntCast(EmitScalarExpr(E->getArg(1)), Int128Ty, IsSigned);
+
+    Value *MulResult, *HigherBits;
+    if (IsSigned) {
+      MulResult = Builder.CreateNSWMul(LHS, RHS);
+      HigherBits = Builder.CreateAShr(MulResult, 64);
+    } else {
+      MulResult = Builder.CreateNUWMul(LHS, RHS);
+      HigherBits = Builder.CreateLShr(MulResult, 64);
+    }
+    HigherBits = Builder.CreateIntCast(HigherBits, ResType, IsSigned);
+
+    return HigherBits;
+  }
+
   // Handle MSVC intrinsics before argument evaluation to prevent double
   // evaluation.
   if (Optional<MSVCIntrin> MsvcIntId = translateAarch64ToMsvcIntrin(BuiltinID))