Use constant offset where possible

Author: tannergooding

src/coreclr/jit/lowerarmarch.cpp

@@ -1260,15 +1260,16 @@ GenTree* Lowering::LowerHWIntrinsic(GenTreeHWIntrinsic* node)
             GenTree* op1 = node->Op(1);
             GenTree* op2 = node->Op(2);
 
-            unsigned  simdSize     = node->GetSimdSize();
-            var_types simdBaseType = node->GetSimdBaseType();
-            var_types simdType     = Compiler::getSIMDTypeForSize(simdSize);
-            unsigned  scale        = genTypeSize(simdBaseType);
-
             bool isContainableMemory = IsContainableMemoryOp(op1) && IsSafeToContainMem(node, op1);
 
             if (isContainableMemory || !op2->OperIsConst())
             {
+                unsigned  simdSize     = node->GetSimdSize();
+                var_types simdBaseType = node->GetSimdBaseType();
+                var_types simdType     = Compiler::getSIMDTypeForSize(simdSize);
+                unsigned  scale        = genTypeSize(simdBaseType);
+                ssize_t   offset       = 0;
+
                 // We're either already loading from memory or we need to since
                 // we don't know what actual index is going to be retrieved.
 
@@ -1295,15 +1296,24 @@ GenTree* Lowering::LowerHWIntrinsic(GenTreeHWIntrinsic* node)
                 if (lclNum != BAD_VAR_NUM)
                 {
                     // We need to get the address of the local
-                    op1 = comp->gtNewLclVarAddrNode(lclNum, simdBaseType);
+                    op1 = comp->gtNewLclVarAddrNode(lclNum, TYP_BYREF);
                     BlockRange().InsertBefore(node, op1);
                     LowerNode(op1);
                 }
 
                 // Now that we have a memory op, we need to offset it by op2 * scale
                 assert(op1->isMemoryOp());
 
-                GenTree* addr = new (comp, GT_LEA) GenTreeAddrMode(simdBaseType, op1, op2, scale, 0);
+                if (op2->OperIsConst())
+                {
+                    offset = op2->AsIntCon()->IconValue() * scale;
+                    scale  = 0;
+
+                    BlockRange().Remove(op2);
+                    op2 = nullptr;
+                }
+
+                GenTree* addr = new (comp, GT_LEA) GenTreeAddrMode(op1->TypeGet(), op1, op2, scale, offset);
                 BlockRange().InsertBefore(node, addr);
                 LowerNode(addr);