ValueTracking: Fix bugs in isKnownToBeAPowerOfTwo

(add nsw x, (and x, y)) isn't a power of two if x is zero, it's zero
(add nsw x, (xor x, y)) isn't a power of two if y has bits set that aren't set in x

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@185954 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Analysis/ValueTracking.cpp b/lib/Analysis/ValueTracking.cpp
index b3693b35452e6759d0c4764db77c31b93636971b..1b20a25ef26162591a65deba9923a048c649d826 100644 (file)
--- a/lib/Analysis/ValueTracking.cpp
+++ b/lib/Analysis/ValueTracking.cpp
@@ -861,16 +861,14 @@ bool llvm::isKnownToBeAPowerOfTwo(Value *V, bool OrZero, unsigned Depth) {
         // Adding a power of two to the same power of two is a power of two or
         // zero.
         if (BinaryOperator *XBO = dyn_cast<BinaryOperator>(X))
-          if (XBO->getOpcode() == Instruction::And ||
-              XBO->getOpcode() == Instruction::Xor)
+          if (XBO->getOpcode() == Instruction::And)
             if (XBO->getOperand(0) == Y || XBO->getOperand(1) == Y)
-              if (isKnownToBeAPowerOfTwo(Y, /*OrZero*/true, Depth))
+              if (isKnownToBeAPowerOfTwo(Y, OrZero, Depth))
                 return true;
         if (BinaryOperator *YBO = dyn_cast<BinaryOperator>(Y))
-          if (YBO->getOpcode() == Instruction::And ||
-              YBO->getOpcode() == Instruction::Xor)
+          if (YBO->getOpcode() == Instruction::And)
             if (YBO->getOperand(0) == X || YBO->getOperand(1) == X)
-              if (isKnownToBeAPowerOfTwo(X, /*OrZero*/true, Depth))
+              if (isKnownToBeAPowerOfTwo(X, OrZero, Depth))
                 return true;
       }
 

diff --git a/test/Transforms/InstCombine/rem.ll b/test/Transforms/InstCombine/rem.ll
index 2b49385b9227f4103fd0184fe4d5f092450e23c8..808d51eba1d29c916ef04cf71fd20d241991760e 100644 (file)
--- a/test/Transforms/InstCombine/rem.ll
+++ b/test/Transforms/InstCombine/rem.ll
@@ -163,18 +163,3 @@ define i32 @test16(i32 %x, i32 %y) {
        %rem = urem i32 %x, %add
        ret i32 %rem
 }
-
-define i32 @test17(i16 %x, i32 %y) {
-; CHECK: @test17
-; CHECK-NEXT: [[AND:%.*]] = and i16 %x, 4
-; CHECK-NEXT: [[EXT:%.*]] = zext i16 [[AND]] to i32
-; CHECK-NEXT: [[SHL:%.*]] = shl nuw nsw i32 [[EXT]], 3
-; CHECK-NEXT: [[XOR:%.*]] = xor i32 [[SHL]], 63
-; CHECK-NEXT: [[REM:%.*]] = and i32 [[XOR]], %y
-; CHECK-NEXT: ret i32 [[REM]]
-       %1 = and i16 %x, 4
-       %2 = icmp ne i16 %1, 0
-       %3 = select i1 %2, i32 32, i32 64
-       %4 = urem i32 %y, %3
-       ret i32 %4
-}