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refactor a bunch of code out of visitICmpInstWithInstAndIntCst into its own

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routine.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@37679 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2007-06-20 23:46:26 +00:00
parent 3eaca716bf
commit 562ef78df2
1 changed files with 134 additions and 123 deletions
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257
lib/Transforms/Scalar/InstructionCombining.cpp
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@ -189,6 +189,8 @@ namespace {
Instruction *visitICmpInstWithInstAndIntCst(ICmpInst &ICI,
Instruction *LHS,
ConstantInt *RHS);
Instruction *FoldICmpDivCst(ICmpInst &ICI, BinaryOperator *DivI,
ConstantInt *DivRHS);
Instruction *FoldGEPICmp(User *GEPLHS, Value *RHS,
ICmpInst::Predicate Cond, Instruction &I);
@ -5109,6 +5111,134 @@ Instruction *InstCombiner::visitICmpInst(ICmpInst &I) {
return Changed ? &I : 0;
}
/// FoldICmpDivCst - Fold "icmp pred, ([su]div X, DivRHS), CmpRHS" where DivRHS
/// and CmpRHS are both known to be integer constants.
Instruction *InstCombiner::FoldICmpDivCst(ICmpInst &ICI, BinaryOperator *DivI,
ConstantInt *DivRHS) {
ConstantInt *CmpRHS = cast<ConstantInt>(ICI.getOperand(1));
const APInt &CmpRHSV = CmpRHS->getValue();
// FIXME: If the operand types don't match the type of the divide
// then don't attempt this transform. The code below doesn't have the
// logic to deal with a signed divide and an unsigned compare (and
// vice versa). This is because (x /s C1) <s C2 produces different
// results than (x /s C1) <u C2 or (x /u C1) <s C2 or even
// (x /u C1) <u C2. Simply casting the operands and result won't
// work. :( The if statement below tests that condition and bails
// if it finds it.
bool DivIsSigned = DivI->getOpcode() == Instruction::SDiv;
if (!ICI.isEquality() && DivIsSigned != ICI.isSignedPredicate())
return 0;
if (DivRHS->isZero())
return 0; // Don't hack on div by zero
// Initialize the variables that will indicate the nature of the
// range check.
bool LoOverflow = false, HiOverflow = false;
ConstantInt *LoBound = 0, *HiBound = 0;
// Compute Prod = CI * DivRHS. We are essentially solving an equation
// of form X/C1=C2. We solve for X by multiplying C1 (DivRHS) and
// C2 (CI). By solving for X we can turn this into a range check
// instead of computing a divide.
ConstantInt *Prod = Multiply(CmpRHS, DivRHS);
// Determine if the product overflows by seeing if the product is
// not equal to the divide. Make sure we do the same kind of divide
// as in the LHS instruction that we're folding.
bool ProdOV = (DivIsSigned ? ConstantExpr::getSDiv(Prod, DivRHS) :
ConstantExpr::getUDiv(Prod, DivRHS)) != CmpRHS;
// Get the ICmp opcode
ICmpInst::Predicate predicate = ICI.getPredicate();
if (!DivIsSigned) { // udiv
LoBound = Prod;
LoOverflow = ProdOV;
HiOverflow = ProdOV || AddWithOverflow(HiBound, LoBound, DivRHS, false);
} else if (DivRHS->getValue().isPositive()) { // Divisor is > 0.
if (CmpRHSV == 0) { // (X / pos) op 0
// Can't overflow.
LoBound = cast<ConstantInt>(ConstantExpr::getNeg(SubOne(DivRHS)));
HiBound = DivRHS;
} else if (CmpRHSV.isPositive()) { // (X / pos) op pos
LoBound = Prod;
LoOverflow = ProdOV;
HiOverflow = ProdOV || AddWithOverflow(HiBound, Prod, DivRHS, true);
} else { // (X / pos) op neg
Constant *DivRHSH = ConstantExpr::getNeg(SubOne(DivRHS));
LoOverflow = AddWithOverflow(LoBound, Prod,
cast<ConstantInt>(DivRHSH), true);
HiBound = AddOne(Prod);
HiOverflow = ProdOV;
}
} else { // Divisor is < 0.
if (CmpRHSV == 0) { // (X / neg) op 0
LoBound = AddOne(DivRHS);
HiBound = cast<ConstantInt>(ConstantExpr::getNeg(DivRHS));
if (HiBound == DivRHS)
return 0; // - INTMIN = INTMIN
} else if (CmpRHSV.isPositive()) { // (X / neg) op pos
HiOverflow = LoOverflow = ProdOV;
if (!LoOverflow)
LoOverflow = AddWithOverflow(LoBound, Prod, AddOne(DivRHS),
true);
HiBound = AddOne(Prod);
} else { // (X / neg) op neg
LoBound = Prod;
LoOverflow = HiOverflow = ProdOV;
HiBound = Subtract(Prod, DivRHS);
}
// Dividing by a negate swaps the condition.
predicate = ICmpInst::getSwappedPredicate(predicate);
}
Value *X = DivI->getOperand(0);
switch (predicate) {
default: assert(0 && "Unhandled icmp opcode!");
case ICmpInst::ICMP_EQ:
if (LoOverflow && HiOverflow)
return ReplaceInstUsesWith(ICI, ConstantInt::getFalse());
else if (HiOverflow)
return new ICmpInst(DivIsSigned ? ICmpInst::ICMP_SGE :
ICmpInst::ICMP_UGE, X, LoBound);
else if (LoOverflow)
return new ICmpInst(DivIsSigned ? ICmpInst::ICMP_SLT :
ICmpInst::ICMP_ULT, X, HiBound);
else
return InsertRangeTest(X, LoBound, HiBound, DivIsSigned,
true, ICI);
case ICmpInst::ICMP_NE:
if (LoOverflow && HiOverflow)
return ReplaceInstUsesWith(ICI, ConstantInt::getTrue());
else if (HiOverflow)
return new ICmpInst(DivIsSigned ? ICmpInst::ICMP_SLT :
ICmpInst::ICMP_ULT, X, LoBound);
else if (LoOverflow)
return new ICmpInst(DivIsSigned ? ICmpInst::ICMP_SGE :
ICmpInst::ICMP_UGE, X, HiBound);
else
return InsertRangeTest(X, LoBound, HiBound, DivIsSigned,
false, ICI);
case ICmpInst::ICMP_ULT:
case ICmpInst::ICMP_SLT:
if (LoOverflow)
return ReplaceInstUsesWith(ICI, ConstantInt::getFalse());
return new ICmpInst(predicate, X, LoBound);
case ICmpInst::ICMP_UGT:
case ICmpInst::ICMP_SGT:
if (HiOverflow)
return ReplaceInstUsesWith(ICI, ConstantInt::getFalse());
if (predicate == ICmpInst::ICMP_UGT)
return new ICmpInst(ICmpInst::ICMP_UGE, X, HiBound);
else
return new ICmpInst(ICmpInst::ICMP_SGE, X, HiBound);
}
}
/// visitICmpInstWithInstAndIntCst - Handle "icmp (instr, intcst)".
///
Instruction *InstCombiner::visitICmpInstWithInstAndIntCst(ICmpInst &ICI,
@ -5357,129 +5487,10 @@ Instruction *InstCombiner::visitICmpInstWithInstAndIntCst(ICmpInst &ICI,
// checked. If there is an overflow on the low or high side, remember
// it, otherwise compute the range [low, hi) bounding the new value.
// See: InsertRangeTest above for the kinds of replacements possible.
if (ConstantInt *DivRHS = dyn_cast<ConstantInt>(LHSI->getOperand(1))) {
// FIXME: If the operand types don't match the type of the divide
// then don't attempt this transform. The code below doesn't have the
// logic to deal with a signed divide and an unsigned compare (and
// vice versa). This is because (x /s C1) <s C2 produces different
// results than (x /s C1) <u C2 or (x /u C1) <s C2 or even
// (x /u C1) <u C2. Simply casting the operands and result won't
// work. :( The if statement below tests that condition and bails
// if it finds it.
bool DivIsSigned = LHSI->getOpcode() == Instruction::SDiv;
if (!ICI.isEquality() && DivIsSigned != ICI.isSignedPredicate())
break;
if (DivRHS->isZero())
break; // Don't hack on div by zero
// Initialize the variables that will indicate the nature of the
// range check.
bool LoOverflow = false, HiOverflow = false;
ConstantInt *LoBound = 0, *HiBound = 0;
// Compute Prod = CI * DivRHS. We are essentially solving an equation
// of form X/C1=C2. We solve for X by multiplying C1 (DivRHS) and
// C2 (CI). By solving for X we can turn this into a range check
// instead of computing a divide.
ConstantInt *Prod = Multiply(RHS, DivRHS);
// Determine if the product overflows by seeing if the product is
// not equal to the divide. Make sure we do the same kind of divide
// as in the LHS instruction that we're folding.
bool ProdOV = (DivIsSigned ? ConstantExpr::getSDiv(Prod, DivRHS) :
ConstantExpr::getUDiv(Prod, DivRHS)) != RHS;
// Get the ICmp opcode
ICmpInst::Predicate predicate = ICI.getPredicate();
if (!DivIsSigned) { // udiv
LoBound = Prod;
LoOverflow = ProdOV;
HiOverflow = ProdOV ||
AddWithOverflow(HiBound, LoBound, DivRHS, false);
} else if (DivRHS->getValue().isPositive()) { // Divisor is > 0.
if (RHSV == 0) { // (X / pos) op 0
// Can't overflow.
LoBound = cast<ConstantInt>(ConstantExpr::getNeg(SubOne(DivRHS)));
HiBound = DivRHS;
} else if (RHSV.isPositive()) { // (X / pos) op pos
LoBound = Prod;
LoOverflow = ProdOV;
HiOverflow = ProdOV ||
AddWithOverflow(HiBound, Prod, DivRHS, true);
} else { // (X / pos) op neg
Constant *DivRHSH = ConstantExpr::getNeg(SubOne(DivRHS));
LoOverflow = AddWithOverflow(LoBound, Prod,
cast<ConstantInt>(DivRHSH), true);
HiBound = AddOne(Prod);
HiOverflow = ProdOV;
}
} else { // Divisor is < 0.
if (RHSV == 0) { // (X / neg) op 0
LoBound = AddOne(DivRHS);
HiBound = cast<ConstantInt>(ConstantExpr::getNeg(DivRHS));
if (HiBound == DivRHS)
LoBound = 0; // - INTMIN = INTMIN
} else if (RHSV.isPositive()) { // (X / neg) op pos
HiOverflow = LoOverflow = ProdOV;
if (!LoOverflow)
LoOverflow = AddWithOverflow(LoBound, Prod, AddOne(DivRHS),
true);
HiBound = AddOne(Prod);
} else { // (X / neg) op neg
LoBound = Prod;
LoOverflow = HiOverflow = ProdOV;
HiBound = Subtract(Prod, DivRHS);
}
// Dividing by a negate swaps the condition.
predicate = ICmpInst::getSwappedPredicate(predicate);
}
if (LoBound) {
Value *X = LHSI->getOperand(0);
switch (predicate) {
default: assert(0 && "Unhandled icmp opcode!");
case ICmpInst::ICMP_EQ:
if (LoOverflow && HiOverflow)
return ReplaceInstUsesWith(ICI, ConstantInt::getFalse());
else if (HiOverflow)
return new ICmpInst(DivIsSigned ? ICmpInst::ICMP_SGE :
ICmpInst::ICMP_UGE, X, LoBound);
else if (LoOverflow)
return new ICmpInst(DivIsSigned ? ICmpInst::ICMP_SLT :
ICmpInst::ICMP_ULT, X, HiBound);
else
return InsertRangeTest(X, LoBound, HiBound, DivIsSigned,
true, ICI);
case ICmpInst::ICMP_NE:
if (LoOverflow && HiOverflow)
return ReplaceInstUsesWith(ICI, ConstantInt::getTrue());
else if (HiOverflow)
return new ICmpInst(DivIsSigned ? ICmpInst::ICMP_SLT :
ICmpInst::ICMP_ULT, X, LoBound);
else if (LoOverflow)
return new ICmpInst(DivIsSigned ? ICmpInst::ICMP_SGE :
ICmpInst::ICMP_UGE, X, HiBound);
else
return InsertRangeTest(X, LoBound, HiBound, DivIsSigned,
false, ICI);
case ICmpInst::ICMP_ULT:
case ICmpInst::ICMP_SLT:
if (LoOverflow)
return ReplaceInstUsesWith(ICI, ConstantInt::getFalse());
return new ICmpInst(predicate, X, LoBound);
case ICmpInst::ICMP_UGT:
case ICmpInst::ICMP_SGT:
if (HiOverflow)
return ReplaceInstUsesWith(ICI, ConstantInt::getFalse());
if (predicate == ICmpInst::ICMP_UGT)
return new ICmpInst(ICmpInst::ICMP_UGE, X, HiBound);
else
return new ICmpInst(ICmpInst::ICMP_SGE, X, HiBound);
}
}
}
if (ConstantInt *DivRHS = dyn_cast<ConstantInt>(LHSI->getOperand(1)))
if (Instruction *R = FoldICmpDivCst(ICI, cast<BinaryOperator>(LHSI),
DivRHS))
return R;
break;
}