[PATCH] Added InstCombine for ((1 << X) & C) pattern

[Dinesh Dwivedi]

================
Comment at: lib/Transforms/InstCombine/InstCombineCompares.cpp:2542-2550
@@ -2541,1 +2541,11 @@
+
+          if (!ValToCheck.isPowerOf2()) {
+            Pred = ICmpInst::ICMP_UGE;
+            ++ValToCheck;
+          }
+
+          if (ValToCheck.isPowerOf2()) {
+            unsigned CVal = ValToCheck.countTrailingZeros();
+            return new ICmpInst(Pred, X, ConstantInt::get(X->getType(), CVal));
+          }
         }
----------------
Benjamin Kramer wrote:
> I think it would be better to generate an ICMP_UGT directly instead of emitting an ICMP_UGE which is turned into ugt later on.
done

================
Comment at: lib/Transforms/InstCombine/InstCombineCompares.cpp:2589-2597
@@ -2578,1 +2588,11 @@
+
+          if (!ValToCheck.isPowerOf2()) {
+            Pred = ICmpInst::ICMP_ULT;
+            ++ValToCheck;
+          }
+
+          if (ValToCheck.isPowerOf2()) {
+            unsigned CVal = ValToCheck.countTrailingZeros();
+            return new ICmpInst(Pred, X, ConstantInt::get(X->getType(), CVal));
+          }
         }
----------------
Benjamin Kramer wrote:
> Same here.
This is already using ULT. Updated code to have symmetry with ICMP_EQ case.

http://reviews.llvm.org/D3678