Recognize MUL_LONG in lowering for ARM64

src/coreclr/jit/lower.cpp

@@ -144,11 +144,10 @@ GenTree* Lowering::LowerNode(GenTree* node)
 
         case GT_MUL:
         case GT_MULHI:
-#if defined(TARGET_X86)
+#if defined(TARGET_X86) || defined(TARGET_ARM64)
         case GT_MUL_LONG:
 #endif
-            ContainCheckMul(node->AsOp());
-            break;
+            return LowerMul(node->AsOp());
 
         case GT_UDIV:
         case GT_UMOD:

src/coreclr/jit/lower.h

@@ -296,6 +296,7 @@ class Lowering final : public Phase
     void LowerIndir(GenTreeIndir* ind);
     void LowerStoreIndir(GenTreeStoreInd* node);
     GenTree* LowerAdd(GenTreeOp* node);
+    GenTree* LowerMul(GenTreeOp* mul);
     bool LowerUnsignedDivOrMod(GenTreeOp* divMod);
     GenTree* LowerConstIntDivOrMod(GenTree* node);
     GenTree* LowerSignedDivOrMod(GenTree* node);

src/coreclr/jit/lowerarmarch.cpp

@@ -223,6 +223,60 @@ void Lowering::LowerStoreIndir(GenTreeStoreInd* node)
     ContainCheckStoreIndir(node);
 }
 
+//------------------------------------------------------------------------
+// LowerMul: Lower a GT_MUL/GT_MULHI/GT_MUL_LONG node.
+//
+// For ARM64 recognized GT_MULs that can be turned into GT_MUL_LONGs, as
+// those are cheaper. Performs contaiment checks.
+//
+// Arguments:
+//    mul - The node to lower
+//
+// Return Value:
+//    The next node to lower.
+//
+GenTree* Lowering::LowerMul(GenTreeOp* mul)
+{
+    assert(mul->OperIsMul());
+
+#ifdef TARGET_ARM64
+    if (comp->opts.OptimizationEnabled() && mul->OperIs(GT_MUL) && mul->IsValidLongMul())
+    {
+        GenTreeCast* op1 = mul->gtGetOp1()->AsCast();
+        GenTree*     op2 = mul->gtGetOp2();
+
+        mul->ClearOverflow();
+        mul->ClearUnsigned();
+        if (op1->IsUnsigned())
+        {
+            mul->SetUnsigned();
+        }
+
+        mul->gtOp1 = op1->CastOp();
+        BlockRange().Remove(op1);
+
+        if (op2->OperIs(GT_CAST))
+        {
+            mul->gtOp2 = op2->AsCast()->CastOp();
+            BlockRange().Remove(op2);
+        }
+        else
+        {
+            assert(op2->IsIntegralConst());
+            assert(FitsIn<int32_t>(op2->AsIntConCommon()->IntegralValue()));
+
+            op2->ChangeType(TYP_INT);
+        }
+
+        mul->ChangeOper(GT_MUL_LONG);
+    }
+#endif // TARGET_ARM64
+
+    ContainCheckMul(mul);
+
+    return mul->gtNext;
+}
+
 //------------------------------------------------------------------------
 // LowerBlockStore: Lower a block store node
 //

src/coreclr/jit/lowerxarch.cpp

@@ -170,6 +170,26 @@ void Lowering::LowerStoreIndir(GenTreeStoreInd* node)
     ContainCheckStoreIndir(node);
 }
 
+//------------------------------------------------------------------------
+// LowerMul: Lower a GT_MUL/GT_MULHI/GT_MUL_LONG node.
+//
+// Currently only performs containment checks.
+//
+// Arguments:
+//    mul - The node to lower
+//
+// Return Value:
+//    The next node to lower.
+//
+GenTree* Lowering::LowerMul(GenTreeOp* mul)
+{
+    assert(mul->OperIsMul());
+
+    ContainCheckMul(mul);
+
+    return mul->gtNext;
+}
+
 //------------------------------------------------------------------------
 // LowerBlockStore: Lower a block store node
 //