Index: llvm/trunk/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
===================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
@@ -533,7 +533,8 @@
       // Right fill the mask of bits for this ADD/SUB to demand the most
       // significant bit and all those below it.
       APInt DemandedFromOps(APInt::getLowBitsSet(BitWidth, BitWidth-NLZ));
-      if (SimplifyDemandedBits(I->getOperandUse(0), DemandedFromOps,
+      if (ShrinkDemandedConstant(I, 0, DemandedFromOps) ||
+          SimplifyDemandedBits(I->getOperandUse(0), DemandedFromOps,
                                LHSKnownZero, LHSKnownOne, Depth + 1) ||
           ShrinkDemandedConstant(I, 1, DemandedFromOps) ||
           SimplifyDemandedBits(I->getOperandUse(1), DemandedFromOps,
Index: llvm/trunk/test/Transforms/InstCombine/sub.ll
===================================================================
--- llvm/trunk/test/Transforms/InstCombine/sub.ll
+++ llvm/trunk/test/Transforms/InstCombine/sub.ll
@@ -701,3 +701,46 @@
   ret i8 %sub
 }
 
+define i32 @test49(i32 %X) {
+; CHECK-LABEL: @test49(
+; CHECK-NEXT:    [[SUB:%.*]] = sub i32 1, [[X:%.*]]
+; CHECK-NEXT:    [[RES:%.*]] = and i32 [[SUB]], 64
+; CHECK-NEXT:    ret i32 [[RES]]
+;
+  %sub = sub i32 129, %X
+  %res = and i32 %sub, 64
+  ret i32 %res
+}
+
+define i32 @test50(i32 %X) {
+; CHECK-LABEL: @test50(
+; CHECK-NEXT:    [[SUB:%.*]] = sub i32 1, [[X:%.*]]
+; CHECK-NEXT:    [[RES:%.*]] = and i32 [[SUB]], 127
+; CHECK-NEXT:    ret i32 [[RES]]
+;
+  %sub = sub i32 129, %X
+  %res = and i32 %sub, 127
+  ret i32 %res
+}
+
+define i32 @test51(i32 %X) {
+; CHECK-LABEL: @test51(
+; CHECK-NEXT:    [[SUB:%.*]] = sub i32 126, [[X:%.*]]
+; CHECK-NEXT:    [[RES:%.*]] = and i32 [[SUB]], 64
+; CHECK-NEXT:    ret i32 [[RES]]
+;
+  %sub = sub i32 254, %X
+  %res = and i32 %sub, 64
+  ret i32 %res
+}
+
+define i32 @test52(i32 %X) {
+; CHECK-LABEL: @test52(
+; CHECK-NEXT:    [[SUB:%.*]] = sub i32 126, [[X:%.*]]
+; CHECK-NEXT:    [[RES:%.*]] = and i32 [[SUB]], 127
+; CHECK-NEXT:    ret i32 [[RES]]
+;
+  %sub = sub i32 254, %X
+  %res = and i32 %sub, 127
+  ret i32 %res
+}