[llvm] r185954 - ValueTracking: Fix bugs in isKnownToBeAPowerOfTwo

[David Majnemer]

Author: majnemer
Date: Tue Jul  9 13:11:10 2013
New Revision: 185954

URL: http://llvm.org/viewvc/llvm-project?rev=185954&view=rev
Log:
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

Modified:
    llvm/trunk/lib/Analysis/ValueTracking.cpp
    llvm/trunk/test/Transforms/InstCombine/rem.ll

Modified: llvm/trunk/lib/Analysis/ValueTracking.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/ValueTracking.cpp?rev=185954&r1=185953&r2=185954&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/ValueTracking.cpp (original)
+++ llvm/trunk/lib/Analysis/ValueTracking.cpp Tue Jul  9 13:11:10 2013
@@ -861,16 +861,14 @@ bool llvm::isKnownToBeAPowerOfTwo(Value
         // 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;
       }
 

Modified: llvm/trunk/test/Transforms/InstCombine/rem.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/rem.ll?rev=185954&r1=185953&r2=185954&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/rem.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/rem.ll Tue Jul  9 13:11:10 2013
@@ -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
-}