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[NFC] Move functon from IndVarSimplify to SCEV 

This function can be reused in other places.

Differential Revision: https://reviews.llvm.org/D87274
Reviewed By: fhahn, lebedev.ri
This commit is contained in:
Max Kazantsev 2020-09-09 11:20:59 +07:00
parent 1bb1eac6b1
commit 795e4ee9d2
3 changed files with 31 additions and 31 deletions
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5
llvm/include/llvm/Analysis/ScalarEvolution.h
View File

@ -768,6 +768,11 @@ public:
return getBackedgeTakenCount(L, ConstantMaximum);
}
/// Return a symbolic upper bound for the backedge taken count of the loop.
/// This is more general than getConstantMaxBackedgeTakenCount as it returns
/// an arbitrary expression as opposed to only constants.
const SCEV* computeMaxBackedgeTakenCount(const Loop *L);
/// Return true if the backedge taken count is either the value returned by
/// getConstantMaxBackedgeTakenCount or zero.
bool isBackedgeTakenCountMaxOrZero(const Loop *L);

25
llvm/lib/Analysis/ScalarEvolution.cpp
View File

@ -12506,3 +12506,28 @@ bool ScalarEvolution::matchURem(const SCEV *Expr, const SCEV *&LHS,
MatchURemWithDivisor(getNegativeSCEV(Mul->getOperand(0)));
return false;
}
const SCEV* ScalarEvolution::computeMaxBackedgeTakenCount(const Loop *L) {
SmallVector<BasicBlock*, 16> ExitingBlocks;
L->getExitingBlocks(ExitingBlocks);
// Form an expression for the maximum exit count possible for this loop. We
// merge the max and exact information to approximate a version of
// getConstantMaxBackedgeTakenCount which isn't restricted to just constants.
SmallVector<const SCEV*, 4> ExitCounts;
for (BasicBlock *ExitingBB : ExitingBlocks) {
const SCEV *ExitCount = getExitCount(L, ExitingBB);
if (isa<SCEVCouldNotCompute>(ExitCount))
ExitCount = getExitCount(L, ExitingBB,
ScalarEvolution::ConstantMaximum);
if (!isa<SCEVCouldNotCompute>(ExitCount)) {
assert(DT.dominates(ExitingBB, L->getLoopLatch()) &&
"We should only have known counts for exiting blocks that "
"dominate latch!");
ExitCounts.push_back(ExitCount);
}
}
if (ExitCounts.empty())
return getCouldNotCompute();
return getUMinFromMismatchedTypes(ExitCounts);
}

32
llvm/lib/Transforms/Scalar/IndVarSimplify.cpp
View File

@ -2329,36 +2329,6 @@ bool IndVarSimplify::sinkUnusedInvariants(Loop *L) {
return MadeAnyChanges;
}
/// Return a symbolic upper bound for the backedge taken count of the loop.
/// This is more general than getConstantMaxBackedgeTakenCount as it returns
/// an arbitrary expression as opposed to only constants.
/// TODO: Move into the ScalarEvolution class.
static const SCEV* getMaxBackedgeTakenCount(ScalarEvolution &SE,
DominatorTree &DT, Loop *L) {
SmallVector<BasicBlock*, 16> ExitingBlocks;
L->getExitingBlocks(ExitingBlocks);
// Form an expression for the maximum exit count possible for this loop. We
// merge the max and exact information to approximate a version of
// getConstantMaxBackedgeTakenCount which isn't restricted to just constants.
SmallVector<const SCEV*, 4> ExitCounts;
for (BasicBlock *ExitingBB : ExitingBlocks) {
const SCEV *ExitCount = SE.getExitCount(L, ExitingBB);
if (isa<SCEVCouldNotCompute>(ExitCount))
ExitCount = SE.getExitCount(L, ExitingBB,
ScalarEvolution::ConstantMaximum);
if (!isa<SCEVCouldNotCompute>(ExitCount)) {
assert(DT.dominates(ExitingBB, L->getLoopLatch()) &&
"We should only have known counts for exiting blocks that "
"dominate latch!");
ExitCounts.push_back(ExitCount);
}
}
if (ExitCounts.empty())
return SE.getCouldNotCompute();
return SE.getUMinFromMismatchedTypes(ExitCounts);
}
bool IndVarSimplify::optimizeLoopExits(Loop *L, SCEVExpander &Rewriter) {
SmallVector<BasicBlock*, 16> ExitingBlocks;
L->getExitingBlocks(ExitingBlocks);
@ -2391,7 +2361,7 @@ bool IndVarSimplify::optimizeLoopExits(Loop *L, SCEVExpander &Rewriter) {
return false;
// Get a symbolic upper bound on the loop backedge taken count.
const SCEV *MaxExitCount = getMaxBackedgeTakenCount(*SE, *DT, L);
const SCEV *MaxExitCount = SE->computeMaxBackedgeTakenCount(L);
if (isa<SCEVCouldNotCompute>(MaxExitCount))
return false;