diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp --- a/llvm/lib/Analysis/ValueTracking.cpp +++ b/llvm/lib/Analysis/ValueTracking.cpp @@ -2132,6 +2132,11 @@ case Intrinsic::smin: return isKnownToBeAPowerOfTwo(II->getArgOperand(1), OrZero, Depth, Q) && isKnownToBeAPowerOfTwo(II->getArgOperand(0), OrZero, Depth, Q); + // bswap/bitreverse just move around bits, but don't change any 1s/0s + // thus dont change pow2/non-pow2 status. + case Intrinsic::bitreverse: + case Intrinsic::bswap: + return isKnownToBeAPowerOfTwo(II->getArgOperand(0), OrZero, Depth, Q); default: break; } diff --git a/llvm/test/Analysis/ValueTracking/known-power-of-two.ll b/llvm/test/Analysis/ValueTracking/known-power-of-two.ll --- a/llvm/test/Analysis/ValueTracking/known-power-of-two.ll +++ b/llvm/test/Analysis/ValueTracking/known-power-of-two.ll @@ -84,7 +84,8 @@ ; CHECK-SAME: (i16 [[X:%.*]], i16 [[Y:%.*]]) { ; CHECK-NEXT: [[XP2:%.*]] = shl i16 4, [[X]] ; CHECK-NEXT: [[XX:%.*]] = call i16 @llvm.bswap.i16(i16 [[XP2]]) -; CHECK-NEXT: [[R:%.*]] = urem i16 [[Y]], [[XX]] +; CHECK-NEXT: [[TMP1:%.*]] = add i16 [[XX]], -1 +; CHECK-NEXT: [[R:%.*]] = and i16 [[TMP1]], [[Y]] ; CHECK-NEXT: ret i16 [[R]] ; %xp2 = shl i16 4, %x @@ -115,7 +116,7 @@ ; CHECK-NEXT: [[XP2:%.*]] = shl nuw i16 1, [[X]] ; CHECK-NEXT: [[XX:%.*]] = call i16 @llvm.bswap.i16(i16 [[XP2]]) ; CHECK-NEXT: [[AND:%.*]] = and i16 [[XX]], [[Y]] -; CHECK-NEXT: [[R:%.*]] = icmp eq i16 [[AND]], [[XX]] +; CHECK-NEXT: [[R:%.*]] = icmp ne i16 [[AND]], 0 ; CHECK-NEXT: ret i1 [[R]] ; %xp2 = shl i16 1, %x @@ -148,7 +149,8 @@ ; CHECK-SAME: (i16 [[X:%.*]], i16 [[Y:%.*]]) { ; CHECK-NEXT: [[XP2:%.*]] = shl i16 4, [[X]] ; CHECK-NEXT: [[XX:%.*]] = call i16 @llvm.bitreverse.i16(i16 [[XP2]]) -; CHECK-NEXT: [[R:%.*]] = urem i16 [[Y]], [[XX]] +; CHECK-NEXT: [[TMP1:%.*]] = add nsw i16 [[XX]], -1 +; CHECK-NEXT: [[R:%.*]] = and i16 [[TMP1]], [[Y]] ; CHECK-NEXT: ret i16 [[R]] ; %xp2 = shl i16 4, %x @@ -179,7 +181,7 @@ ; CHECK-NEXT: [[XP2:%.*]] = shl nuw i16 1, [[X]] ; CHECK-NEXT: [[XX:%.*]] = call i16 @llvm.bitreverse.i16(i16 [[XP2]]) ; CHECK-NEXT: [[AND:%.*]] = and i16 [[XX]], [[Y]] -; CHECK-NEXT: [[R:%.*]] = icmp eq i16 [[AND]], [[XX]] +; CHECK-NEXT: [[R:%.*]] = icmp ne i16 [[AND]], 0 ; CHECK-NEXT: ret i1 [[R]] ; %xp2 = shl i16 1, %x