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add a comment and fix some consistency issues, converting

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to a signed vs unsigned value depending on the sign of the
constant fp means that we can't distinguish between a 
truly negative number and a positive number so large the
32nd bit is set.  So, do don't this!


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@100283 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2010-04-03 06:41:49 +00:00
parent 43b85273ee
commit bbb91498da
1 changed files with 25 additions and 15 deletions
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40
lib/Transforms/Scalar/IndVarSimplify.cpp
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@ -623,16 +623,17 @@ void IndVarSimplify::SinkUnusedInvariants(Loop *L) {
}
}
/// convertToInt - Convert APF to an integer, if possible.
static bool convertToInt(const APFloat &APF, uint64_t &intVal) {
/// ConvertToSInt - Convert APF to an integer, if possible.
static bool ConvertToSInt(const APFloat &APF, int64_t &IntVal) {
bool isExact = false;
if (&APF.getSemantics() == &APFloat::PPCDoubleDouble)
return false;
if (APF.convertToInteger(&intVal, 32, APF.isNegative(),
APFloat::rmTowardZero, &isExact) != APFloat::opOK)
return false;
if (!isExact)
// See if we can convert this to an int64_t
uint64_t UIntVal;
if (APF.convertToInteger(&UIntVal, 64, true, APFloat::rmTowardZero,
&isExact) != APFloat::opOK || !isExact)
return false;
IntVal = UIntVal;
return true;
}
@ -654,8 +655,8 @@ void IndVarSimplify::HandleFloatingPointIV(Loop *L, PHINode *PN) {
dyn_cast<ConstantFP>(PN->getIncomingValue(IncomingEdge));
if (!InitValueVal) return;
uint64_t InitValue;
if (!convertToInt(InitValueVal->getValueAPF(), InitValue))
int64_t InitValue;
if (!ConvertToSInt(InitValueVal->getValueAPF(), InitValue))
return;
// Check IV increment. Reject this PN if increment operation is not
@ -667,9 +668,9 @@ void IndVarSimplify::HandleFloatingPointIV(Loop *L, PHINode *PN) {
// If this is not an add of the PHI with a constantfp, or if the constant fp
// is not an integer, bail out.
ConstantFP *IncValueVal = dyn_cast<ConstantFP>(Incr->getOperand(1));
uint64_t IntValue;
int64_t IntValue;
if (IncValueVal == 0 || Incr->getOperand(0) != PN ||
!convertToInt(IncValueVal->getValueAPF(), IntValue))
!ConvertToSInt(IncValueVal->getValueAPF(), IntValue))
return;
// Check Incr uses. One user is PN and the other user is an exit condition
@ -694,9 +695,20 @@ void IndVarSimplify::HandleFloatingPointIV(Loop *L, PHINode *PN) {
// If it isn't a comparison with an integer-as-fp (the exit value), we can't
// transform it.
ConstantFP *ExitValueVal = dyn_cast<ConstantFP>(Compare->getOperand(1));
uint64_t ExitValue;
if (ExitValueVal == 0 || !convertToInt(ExitValueVal->getValueAPF(),ExitValue))
int64_t ExitValue;
if (ExitValueVal == 0 ||
!ConvertToSInt(ExitValueVal->getValueAPF(), ExitValue))
return;
// We convert the floating point induction variable to a signed i32 value if
// we can. This is only safe if the comparison will not overflow in a way
// that won't be trapped by the integer equivalent operations. Check for this
// now.
// TODO: We could use i64 if it is native and the range requires it.
const IntegerType *Int32Ty = Type::getInt32Ty(PN->getContext());
// Find new predicate for integer comparison.
CmpInst::Predicate NewPred = CmpInst::BAD_ICMP_PREDICATE;
@ -714,9 +726,7 @@ void IndVarSimplify::HandleFloatingPointIV(Loop *L, PHINode *PN) {
case CmpInst::FCMP_ULE: NewPred = CmpInst::ICMP_SLE; break;
}
const IntegerType *Int32Ty = Type::getInt32Ty(PN->getContext());
// Insert new i32 integer induction variable.
// Insert new integer induction variable.
PHINode *NewPHI = PHINode::Create(Int32Ty, PN->getName()+".int", PN);
NewPHI->addIncoming(ConstantInt::get(Int32Ty, InitValue),
PN->getIncomingBlock(IncomingEdge));