Lower TEST(x, LSH(1, y)) to BT(x, y)

dotnet · Aug 28, 2017 · dc89ba4 · dc89ba4
1 parent fa7a4a3
commit dc89ba4
Showing 1 changed file with 40 additions and 0 deletions.
diff --git a/src/jit/lower.cpp b/src/jit/lower.cpp
@@ -2535,6 +2535,46 @@ void Lowering::LowerCompare(GenTree* cmp)
         }
     }
 
+    if (cmp->OperIs(GT_TEST_EQ, GT_TEST_NE))
+    {
+        GenTree* lsh = cmp->gtGetOp2();
+        LIR::Use cmpUse;
+
+        if (lsh->OperIs(GT_LSH) && varTypeIsIntOrI(lsh->TypeGet()) && lsh->gtGetOp1()->IsIntegralConst(1) &&
+            BlockRange().TryGetUse(cmp, &cmpUse))
+        {
+            genTreeOps condition = cmp->OperIs(GT_TEST_NE) ? GT_LT : GT_GE;
+
+            cmp->SetOper(GT_BT);
+            cmp->gtFlags |= GTF_SET_FLAGS;
+            cmp->gtOp.gtOp2 = lsh->gtGetOp2();
+
+            BlockRange().Remove(lsh->gtGetOp1());
+            BlockRange().Remove(lsh);
+            lsh->gtGetOp2()->ClearContained();
+
+            GenTreeCC* cc;
+
+            if (cmpUse.User()->OperIs(GT_JTRUE))
+            {
+                cmpUse.User()->ChangeOper(GT_JCC);
+                cc              = cmpUse.User()->AsCC();
+                cc->gtCondition = condition;
+            }
+            else
+            {
+                cc = new (comp, GT_SETCC) GenTreeCC(GT_SETCC, condition, TYP_INT);
+                BlockRange().InsertAfter(cmp, cc);
+                cmpUse.ReplaceWith(comp, cc);
+            }
+
+            cc->gtFlags |= GTF_USE_FLAGS | GTF_UNSIGNED;
+
+            ContainCheckBTx(cmp->AsOp());
+            return;
+        }
+    }
+
     if (cmp->gtGetOp1()->TypeGet() == cmp->gtGetOp2()->TypeGet())
     {
         if (varTypeIsSmall(cmp->gtGetOp1()->TypeGet()) && varTypeIsUnsigned(cmp->gtGetOp1()->TypeGet()))