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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

llvm-svn: 185954
This commit is contained in:
David Majnemer 2013-07-09 18:11:10 +00:00
parent 861bef7dd0
commit a92b3c914e
2 changed files with 4 additions and 21 deletions
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10
llvm/lib/Analysis/ValueTracking.cpp
View File

@ -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;
}

15
llvm/test/Transforms/InstCombine/rem.ll
View File

@ -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
}