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APIntify various computations in ScalarEvolution

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llvm-svn: 34780
This commit is contained in:
Reid Spencer 2007-03-01 07:25:48 +00:00
parent 0d77fe7f06
commit 036051c002
1 changed files with 46 additions and 49 deletions
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95
lib/Analysis/ScalarEvolution.cpp
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@ -1176,7 +1176,7 @@ namespace {
/// in the header of its containing loop, we know the loop executes a
/// constant number of times, and the PHI node is just a recurrence
/// involving constants, fold it.
Constant *getConstantEvolutionLoopExitValue(PHINode *PN, uint64_t Its,
Constant *getConstantEvolutionLoopExitValue(PHINode *PN, const APInt& Its,
const Loop *L);
};
}
@ -1729,7 +1729,7 @@ ComputeLoadConstantCompareIterationCount(LoadInst *LI, Constant *RHS,
// Evaluate the condition for this iteration.
Result = ConstantExpr::getICmp(predicate, Result, RHS);
if (!isa<ConstantInt>(Result)) break; // Couldn't decide for sure
if (cast<ConstantInt>(Result)->getZExtValue() == false) {
if (cast<ConstantInt>(Result)->getValue().isMinValue()) {
#if 0
cerr << "\n***\n*** Computed loop count " << *ItCst
<< "\n*** From global " << *GV << "*** BB: " << *L->getHeader()
@ -1824,13 +1824,13 @@ static Constant *EvaluateExpression(Value *V, Constant *PHIVal) {
/// constant number of times, and the PHI node is just a recurrence
/// involving constants, fold it.
Constant *ScalarEvolutionsImpl::
getConstantEvolutionLoopExitValue(PHINode *PN, uint64_t Its, const Loop *L) {
getConstantEvolutionLoopExitValue(PHINode *PN, const APInt& Its, const Loop *L){
std::map<PHINode*, Constant*>::iterator I =
ConstantEvolutionLoopExitValue.find(PN);
if (I != ConstantEvolutionLoopExitValue.end())
return I->second;
if (Its > MaxBruteForceIterations)
if (Its.ugt(APInt(Its.getBitWidth(),MaxBruteForceIterations)))
return ConstantEvolutionLoopExitValue[PN] = 0; // Not going to evaluate it.
Constant *&RetVal = ConstantEvolutionLoopExitValue[PN];
@ -1850,11 +1850,11 @@ getConstantEvolutionLoopExitValue(PHINode *PN, uint64_t Its, const Loop *L) {
return RetVal = 0; // Not derived from same PHI.
// Execute the loop symbolically to determine the exit value.
unsigned IterationNum = 0;
unsigned NumIterations = Its;
if (NumIterations != Its)
return RetVal = 0; // More than 2^32 iterations??
if (Its.getActiveBits() >= 32)
return RetVal = 0; // More than 2^32-1 iterations?? Not doing it!
unsigned NumIterations = Its.getZExtValue(); // must be in range
unsigned IterationNum = 0;
for (Constant *PHIVal = StartCST; ; ++IterationNum) {
if (IterationNum == NumIterations)
return RetVal = PHIVal; // Got exit value!
@ -1904,7 +1904,7 @@ ComputeIterationCountExhaustively(const Loop *L, Value *Cond, bool ExitWhen) {
// Couldn't symbolically evaluate.
if (!CondVal) return UnknownValue;
if (CondVal->getZExtValue() == uint64_t(ExitWhen)) {
if (CondVal->getValue() == uint64_t(ExitWhen)) {
ConstantEvolutionLoopExitValue[PN] = PHIVal;
++NumBruteForceTripCountsComputed;
return SCEVConstant::get(ConstantInt::get(Type::Int32Ty, IterationNum));
@ -1946,7 +1946,7 @@ SCEVHandle ScalarEvolutionsImpl::getSCEVAtScope(SCEV *V, const Loop *L) {
// this is a constant evolving PHI node, get the final value at
// the specified iteration number.
Constant *RV = getConstantEvolutionLoopExitValue(PN,
ICC->getValue()->getZExtValue(),
ICC->getValue()->getValue(),
LI);
if (RV) return SCEVUnknown::get(RV);
}
@ -2063,57 +2063,54 @@ SCEVHandle ScalarEvolutionsImpl::getSCEVAtScope(SCEV *V, const Loop *L) {
static std::pair<SCEVHandle,SCEVHandle>
SolveQuadraticEquation(const SCEVAddRecExpr *AddRec) {
assert(AddRec->getNumOperands() == 3 && "This is not a quadratic chrec!");
SCEVConstant *L = dyn_cast<SCEVConstant>(AddRec->getOperand(0));
SCEVConstant *M = dyn_cast<SCEVConstant>(AddRec->getOperand(1));
SCEVConstant *N = dyn_cast<SCEVConstant>(AddRec->getOperand(2));
SCEVConstant *LC = dyn_cast<SCEVConstant>(AddRec->getOperand(0));
SCEVConstant *MC = dyn_cast<SCEVConstant>(AddRec->getOperand(1));
SCEVConstant *NC = dyn_cast<SCEVConstant>(AddRec->getOperand(2));
// We currently can only solve this if the coefficients are constants.
if (!L || !M || !N) {
if (!LC || !MC || !NC) {
SCEV *CNC = new SCEVCouldNotCompute();
return std::make_pair(CNC, CNC);
}
Constant *C = L->getValue();
Constant *Two = ConstantInt::get(C->getType(), 2);
uint32_t BitWidth = LC->getValue()->getValue().getBitWidth();
APInt L(LC->getValue()->getValue());
APInt M(MC->getValue()->getValue());
APInt N(MC->getValue()->getValue());
APInt Two(BitWidth, 2);
APInt Four(BitWidth, 4);
// Convert from chrec coefficients to polynomial coefficients AX^2+BX+C
// The B coefficient is M-N/2
Constant *B = ConstantExpr::getSub(M->getValue(),
ConstantExpr::getSDiv(N->getValue(),
Two));
// The A coefficient is N/2
Constant *A = ConstantExpr::getSDiv(N->getValue(), Two);
{
using namespace APIntOps;
APInt C(L);
// Convert from chrec coefficients to polynomial coefficients AX^2+BX+C
// The B coefficient is M-N/2
APInt B(M);
B -= sdiv(N,Two);
// Compute the B^2-4ac term.
Constant *SqrtTerm =
ConstantExpr::getMul(ConstantInt::get(C->getType(), 4),
ConstantExpr::getMul(A, C));
SqrtTerm = ConstantExpr::getSub(ConstantExpr::getMul(B, B), SqrtTerm);
// The A coefficient is N/2
APInt A(N);
A = A.sdiv(Two);
// Compute floor(sqrt(B^2-4ac))
uint64_t SqrtValV = cast<ConstantInt>(SqrtTerm)->getZExtValue();
uint64_t SqrtValV2 = (uint64_t)sqrt((double)SqrtValV);
// The square root might not be precise for arbitrary 64-bit integer
// values. Do some sanity checks to ensure it's correct.
if (SqrtValV2*SqrtValV2 > SqrtValV ||
(SqrtValV2+1)*(SqrtValV2+1) <= SqrtValV) {
SCEV *CNC = new SCEVCouldNotCompute();
return std::make_pair(CNC, CNC);
}
// Compute the B^2-4ac term.
APInt SqrtTerm(B);
SqrtTerm *= B;
SqrtTerm -= Four * (A * C);
ConstantInt *SqrtVal = ConstantInt::get(Type::Int64Ty, SqrtValV2);
SqrtTerm = ConstantExpr::getTruncOrBitCast(SqrtVal, SqrtTerm->getType());
// Compute sqrt(B^2-4ac). This is guaranteed to be the nearest
// integer value or else APInt::sqrt() will assert.
APInt SqrtVal(SqrtTerm.sqrt());
Constant *NegB = ConstantExpr::getNeg(B);
Constant *TwoA = ConstantExpr::getMul(A, Two);
// Compute the two solutions for the quadratic formula.
// The divisions must be performed as signed divisions.
APInt NegB(-B);
APInt TwoA( A * Two );
ConstantInt *Solution1 = ConstantInt::get((NegB + SqrtVal).sdiv(TwoA));
ConstantInt *Solution2 = ConstantInt::get((NegB - SqrtVal).sdiv(TwoA));
// The divisions must be performed as signed divisions.
Constant *Solution1 =
ConstantExpr::getSDiv(ConstantExpr::getAdd(NegB, SqrtTerm), TwoA);
Constant *Solution2 =
ConstantExpr::getSDiv(ConstantExpr::getSub(NegB, SqrtTerm), TwoA);
return std::make_pair(SCEVUnknown::get(Solution1),
SCEVUnknown::get(Solution2));
return std::make_pair(SCEVUnknown::get(Solution1),
SCEVUnknown::get(Solution2));
} // end APIntOps namespace
}
/// HowFarToZero - Return the number of times a backedge comparing the specified