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Reapply commit 143028 with a fix: the problem was casting a ConstantExpr Mul

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using BinaryOperator (which only works for instructions) when it should have
been a cast to OverflowingBinaryOperator (which also works for constants).
While there, correct a few other dubious looking uses of BinaryOperator.
Thanks to Chad Rosier for the testcase.  Original commit message:
My super-optimizer noticed that we weren't folding this expression to
true: (x *nsw x) sgt 0, where x = (y | 1).  This occurs in 464.h264ref.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@143125 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Duncan Sands 2011-10-27 19:16:21 +00:00
parent 6eb1ed8c9c
commit 32a43cc0fc
4 changed files with 95 additions and 9 deletions
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5
lib/Analysis/InstructionSimplify.cpp
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@ -758,7 +758,8 @@ static Value *SimplifyMulInst(Value *Op0, Value *Op1, const TargetData *TD,
Value *X = 0, *Y = 0;
if ((match(Op0, m_IDiv(m_Value(X), m_Value(Y))) && Y == Op1) || // (X / Y) * Y
(match(Op1, m_IDiv(m_Value(X), m_Value(Y))) && Y == Op0)) { // Y * (X / Y)
BinaryOperator *Div = cast<BinaryOperator>(Y == Op1 ? Op0 : Op1);
PossiblyExactOperator *Div =
cast<PossiblyExactOperator>(Y == Op1 ? Op0 : Op1);
if (Div->isExact())
return X;
}
@ -842,7 +843,7 @@ static Value *SimplifyDiv(Instruction::BinaryOps Opcode, Value *Op0, Value *Op1,
Value *X = 0, *Y = 0;
if (match(Op0, m_Mul(m_Value(X), m_Value(Y))) && (X == Op1 || Y == Op1)) {
if (Y != Op1) std::swap(X, Y); // Ensure expression is (X * Y) / Y, Y = Op1
BinaryOperator *Mul = cast<BinaryOperator>(Op0);
OverflowingBinaryOperator *Mul = cast<OverflowingBinaryOperator>(Op0);
// If the Mul knows it does not overflow, then we are good to go.
if ((isSigned && Mul->hasNoSignedWrap()) ||
(!isSigned && Mul->hasNoUnsignedWrap()))

56
lib/Analysis/ValueTracking.cpp
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@ -201,9 +201,36 @@ void llvm::ComputeMaskedBits(Value *V, const APInt &Mask,
ComputeMaskedBits(I->getOperand(1), Mask2, KnownZero, KnownOne, TD,Depth+1);
ComputeMaskedBits(I->getOperand(0), Mask2, KnownZero2, KnownOne2, TD,
Depth+1);
assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?");
assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?");
bool isKnownNegative = false;
bool isKnownNonNegative = false;
// If the multiplication is known not to overflow, compute the sign bit.
if (Mask.isNegative() &&
cast<OverflowingBinaryOperator>(I)->hasNoSignedWrap()) {
Value *Op1 = I->getOperand(1), *Op2 = I->getOperand(0);
if (Op1 == Op2) {
// The product of a number with itself is non-negative.
isKnownNonNegative = true;
} else {
bool isKnownNonNegative1 = KnownZero.isNegative();
bool isKnownNonNegative2 = KnownZero2.isNegative();
bool isKnownNegative1 = KnownOne.isNegative();
bool isKnownNegative2 = KnownOne2.isNegative();
// The product of two numbers with the same sign is non-negative.
isKnownNonNegative = (isKnownNegative1 && isKnownNegative2) ||
(isKnownNonNegative1 && isKnownNonNegative2);
// The product of a negative number and a non-negative number is either
// negative or zero.
if (!isKnownNonNegative)
isKnownNegative = (isKnownNegative1 && isKnownNonNegative2 &&
isKnownNonZero(Op2, TD, Depth)) ||
(isKnownNegative2 && isKnownNonNegative1 &&
isKnownNonZero(Op1, TD, Depth));
}
}
// If low bits are zero in either operand, output low known-0 bits.
// Also compute a conserative estimate for high known-0 bits.
// More trickiness is possible, but this is sufficient for the
@ -220,6 +247,12 @@ void llvm::ComputeMaskedBits(Value *V, const APInt &Mask,
KnownZero = APInt::getLowBitsSet(BitWidth, TrailZ) |
APInt::getHighBitsSet(BitWidth, LeadZ);
KnownZero &= Mask;
if (isKnownNonNegative)
KnownZero.setBit(BitWidth - 1);
else if (isKnownNegative)
KnownOne.setBit(BitWidth - 1);
return;
}
case Instruction::UDiv: {
@ -784,7 +817,7 @@ bool llvm::isKnownNonZero(Value *V, const TargetData *TD, unsigned Depth) {
}
// The remaining tests are all recursive, so bail out if we hit the limit.
if (Depth++ == MaxDepth)
if (Depth++ >= MaxDepth)
return false;
unsigned BitWidth = getBitWidth(V->getType(), TD);
@ -802,7 +835,7 @@ bool llvm::isKnownNonZero(Value *V, const TargetData *TD, unsigned Depth) {
// if the lowest bit is shifted off the end.
if (BitWidth && match(V, m_Shl(m_Value(X), m_Value(Y)))) {
// shl nuw can't remove any non-zero bits.
BinaryOperator *BO = cast<BinaryOperator>(V);
OverflowingBinaryOperator *BO = cast<OverflowingBinaryOperator>(V);
if (BO->hasNoUnsignedWrap())
return isKnownNonZero(X, TD, Depth);
@ -816,7 +849,7 @@ bool llvm::isKnownNonZero(Value *V, const TargetData *TD, unsigned Depth) {
// defined if the sign bit is shifted off the end.
else if (match(V, m_Shr(m_Value(X), m_Value(Y)))) {
// shr exact can only shift out zero bits.
BinaryOperator *BO = cast<BinaryOperator>(V);
PossiblyExactOperator *BO = cast<PossiblyExactOperator>(V);
if (BO->isExact())
return isKnownNonZero(X, TD, Depth);
@ -827,7 +860,7 @@ bool llvm::isKnownNonZero(Value *V, const TargetData *TD, unsigned Depth) {
}
// div exact can only produce a zero if the dividend is zero.
else if (match(V, m_IDiv(m_Value(X), m_Value()))) {
BinaryOperator *BO = cast<BinaryOperator>(V);
PossiblyExactOperator *BO = cast<PossiblyExactOperator>(V);
if (BO->isExact())
return isKnownNonZero(X, TD, Depth);
}
@ -868,6 +901,15 @@ bool llvm::isKnownNonZero(Value *V, const TargetData *TD, unsigned Depth) {
if (YKnownNonNegative && isPowerOfTwo(X, TD, /*OrZero*/false, Depth))
return true;
}
// X * Y.
else if (match(V, m_Mul(m_Value(X), m_Value(Y)))) {
OverflowingBinaryOperator *BO = cast<OverflowingBinaryOperator>(V);
// If X and Y are non-zero then so is X * Y as long as the multiplication
// does not overflow.
if ((BO->hasNoSignedWrap() || BO->hasNoUnsignedWrap()) &&
isKnownNonZero(X, TD, Depth) && isKnownNonZero(Y, TD, Depth))
return true;
}
// (C ? X : Y) != 0 if X != 0 and Y != 0.
else if (SelectInst *SI = dyn_cast<SelectInst>(V)) {
if (isKnownNonZero(SI->getTrueValue(), TD, Depth) &&

12
test/Transforms/InstSimplify/2011-10-27-BinOpCrash.ll Normal file
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@ -0,0 +1,12 @@
; RUN: opt < %s -instcombine
@_ZN11xercesc_2_5L11gDigitCharsE = external constant [32 x i16], align 2
@_ZN11xercesc_2_5L10gBaseCharsE = external constant [354 x i16], align 2
@_ZN11xercesc_2_5L17gIdeographicCharsE = external constant [7 x i16], align 2
@_ZN11xercesc_2_5L15gCombiningCharsE = external constant [163 x i16], align 2
define i32 @_ZN11xercesc_2_515XMLRangeFactory11buildRangesEv(i32 %x) {
%a = add i32 %x, add (i32 add (i32 ashr (i32 add (i32 mul (i32 ptrtoint ([32 x i16]* @_ZN11xercesc_2_5L11gDigitCharsE to i32), i32 -1), i32 ptrtoint (i16* getelementptr inbounds ([32 x i16]* @_ZN11xercesc_2_5L11gDigitCharsE, i32 0, i32 30) to i32)), i32 1), i32 ashr (i32 add (i32 mul (i32 ptrtoint ([7 x i16]* @_ZN11xercesc_2_5L17gIdeographicCharsE to i32), i32 -1), i32 ptrtoint (i16* getelementptr inbounds ([7 x i16]* @_ZN11xercesc_2_5L17gIdeographicCharsE, i32 0, i32 4) to i32)), i32 1)), i32 8)
%b = add i32 %a, %x
ret i32 %b
}

31
test/Transforms/InstSimplify/compare.ll
View File

@ -323,3 +323,34 @@ define i1 @and1(i32 %X) {
ret i1 %B
; CHECK: ret i1 false
}
define i1 @mul1(i32 %X) {
; CHECK: @mul1
; Square of a non-zero number is non-zero if there is no overflow.
%Y = or i32 %X, 1
%M = mul nuw i32 %Y, %Y
%C = icmp eq i32 %M, 0
ret i1 %C
; CHECK: ret i1 false
}
define i1 @mul2(i32 %X) {
; CHECK: @mul2
; Square of a non-zero number is positive if there is no signed overflow.
%Y = or i32 %X, 1
%M = mul nsw i32 %Y, %Y
%C = icmp sgt i32 %M, 0
ret i1 %C
; CHECK: ret i1 true
}
define i1 @mul3(i32 %X, i32 %Y) {
; CHECK: @mul3
; Product of non-negative numbers is non-negative if there is no signed overflow.
%XX = mul nsw i32 %X, %X
%YY = mul nsw i32 %Y, %Y
%M = mul nsw i32 %XX, %YY
%C = icmp sge i32 %M, 0
ret i1 %C
; CHECK: ret i1 true
}