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Convert a few more backedge-taken count functions to use BackedgeTakenInfo. 

llvm-svn: 97042
This commit is contained in:
Dan Gohman 2010-02-24 17:31:30 +00:00
parent 4811d004be
commit ba820344e3
2 changed files with 16 additions and 17 deletions
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6
llvm/include/llvm/Analysis/ScalarEvolution.h
View File

@ -305,7 +305,7 @@ namespace llvm {
/// ComputeLoadConstantCompareBackedgeTakenCount - Given an exit condition
/// of 'icmp op load X, cst', try to see if we can compute the
/// backedge-taken count.
const SCEV *
BackedgeTakenInfo
ComputeLoadConstantCompareBackedgeTakenCount(LoadInst *LI,
Constant *RHS,
const Loop *L,
@ -323,12 +323,12 @@ namespace llvm {
/// HowFarToZero - Return the number of times a backedge comparing the
/// specified value to zero will execute. If not computable, return
/// CouldNotCompute.
const SCEV *HowFarToZero(const SCEV *V, const Loop *L);
BackedgeTakenInfo HowFarToZero(const SCEV *V, const Loop *L);
/// HowFarToNonZero - Return the number of times a backedge checking the
/// specified value for nonzero will execute. If not computable, return
/// CouldNotCompute.
const SCEV *HowFarToNonZero(const SCEV *V, const Loop *L);
BackedgeTakenInfo HowFarToNonZero(const SCEV *V, const Loop *L);
/// HowManyLessThans - Return the number of times a backedge containing the
/// specified less-than comparison will execute. If not computable, return

27
llvm/lib/Analysis/ScalarEvolution.cpp
View File

@ -3744,14 +3744,10 @@ ScalarEvolution::ComputeBackedgeTakenCountFromExitCondICmp(const Loop *L,
// Handle common loops like: for (X = "string"; *X; ++X)
if (LoadInst *LI = dyn_cast<LoadInst>(ExitCond->getOperand(0)))
if (Constant *RHS = dyn_cast<Constant>(ExitCond->getOperand(1))) {
const SCEV *ItCnt =
BackedgeTakenInfo ItCnt =
ComputeLoadConstantCompareBackedgeTakenCount(LI, RHS, L, Cond);
if (!isa<SCEVCouldNotCompute>(ItCnt)) {
unsigned BitWidth = getTypeSizeInBits(ItCnt->getType());
return BackedgeTakenInfo(ItCnt,
isa<SCEVConstant>(ItCnt) ? ItCnt :
getConstant(APInt::getMaxValue(BitWidth)-1));
}
if (ItCnt.hasAnyInfo())
return ItCnt;
}
const SCEV *LHS = getSCEV(ExitCond->getOperand(0));
@ -3785,14 +3781,14 @@ ScalarEvolution::ComputeBackedgeTakenCountFromExitCondICmp(const Loop *L,
switch (Cond) {
case ICmpInst::ICMP_NE: { // while (X != Y)
// Convert to: while (X-Y != 0)
const SCEV *TC = HowFarToZero(getMinusSCEV(LHS, RHS), L);
if (!isa<SCEVCouldNotCompute>(TC)) return TC;
BackedgeTakenInfo BTI = HowFarToZero(getMinusSCEV(LHS, RHS), L);
if (BTI.hasAnyInfo()) return BTI;
break;
}
case ICmpInst::ICMP_EQ: { // while (X == Y)
// Convert to: while (X-Y == 0)
const SCEV *TC = HowFarToNonZero(getMinusSCEV(LHS, RHS), L);
if (!isa<SCEVCouldNotCompute>(TC)) return TC;
BackedgeTakenInfo BTI = HowFarToNonZero(getMinusSCEV(LHS, RHS), L);
if (BTI.hasAnyInfo()) return BTI;
break;
}
case ICmpInst::ICMP_SLT: {
@ -3879,7 +3875,7 @@ GetAddressedElementFromGlobal(GlobalVariable *GV,
/// ComputeLoadConstantCompareBackedgeTakenCount - Given an exit condition of
/// 'icmp op load X, cst', try to see if we can compute the backedge
/// execution count.
const SCEV *
ScalarEvolution::BackedgeTakenInfo
ScalarEvolution::ComputeLoadConstantCompareBackedgeTakenCount(
LoadInst *LI,
Constant *RHS,
@ -3888,6 +3884,7 @@ ScalarEvolution::ComputeLoadConstantCompareBackedgeTakenCount(
if (LI->isVolatile()) return getCouldNotCompute();
// Check to see if the loaded pointer is a getelementptr of a global.
// TODO: Use SCEV instead of manually grubbing with GEPs.
GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(LI->getOperand(0));
if (!GEP) return getCouldNotCompute();
@ -4452,7 +4449,8 @@ SolveQuadraticEquation(const SCEVAddRecExpr *AddRec, ScalarEvolution &SE) {
/// HowFarToZero - Return the number of times a backedge comparing the specified
/// value to zero will execute. If not computable, return CouldNotCompute.
const SCEV *ScalarEvolution::HowFarToZero(const SCEV *V, const Loop *L) {
ScalarEvolution::BackedgeTakenInfo
ScalarEvolution::HowFarToZero(const SCEV *V, const Loop *L) {
// If the value is a constant
if (const SCEVConstant *C = dyn_cast<SCEVConstant>(V)) {
// If the value is already zero, the branch will execute zero times.
@ -4532,7 +4530,8 @@ const SCEV *ScalarEvolution::HowFarToZero(const SCEV *V, const Loop *L) {
/// HowFarToNonZero - Return the number of times a backedge checking the
/// specified value for nonzero will execute. If not computable, return
/// CouldNotCompute
const SCEV *ScalarEvolution::HowFarToNonZero(const SCEV *V, const Loop *L) {
ScalarEvolution::BackedgeTakenInfo
ScalarEvolution::HowFarToNonZero(const SCEV *V, const Loop *L) {
// Loops that look like: while (X == 0) are very strange indeed. We don't
// handle them yet except for the trivial case. This could be expanded in the
// future as needed.