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Correct the recursive PHI node handling routines in a way that CANNOT induce

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infinite loops (using the new replaceSymbolicValuesWithConcrete method).

This patch reverts this patch:
http://mail.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20050131/023830.html

... which was an attempted fix for this problem.  Unfortunately, that patch
caused test/Regression/Transforms/IndVarsSimplify/exit_value_tests.llx to fail
and slightly castrated the entire analysis.  This patch fixes it right.

This patch is dedicated to jeffc, for making me deal with this.  :)


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@20146 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2005-02-13 04:37:18 +00:00
parent afc0dc7184
commit 4dc534c7fe
1 changed files with 83 additions and 27 deletions
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110
lib/Analysis/ScalarEvolution.cpp
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@ -144,6 +144,12 @@ bool SCEVCouldNotCompute::hasComputableLoopEvolution(const Loop *L) const {
return false;
}
SCEVHandle SCEVCouldNotCompute::
replaceSymbolicValuesWithConcrete(const SCEVHandle &Sym,
const SCEVHandle &Conc) const {
return this;
}
void SCEVCouldNotCompute::print(std::ostream &OS) const {
OS << "***COULDNOTCOMPUTE***";
}
@ -259,6 +265,33 @@ void SCEVCommutativeExpr::print(std::ostream &OS) const {
OS << ")";
}
SCEVHandle SCEVCommutativeExpr::
replaceSymbolicValuesWithConcrete(const SCEVHandle &Sym,
const SCEVHandle &Conc) const {
for (unsigned i = 0, e = getNumOperands(); i != e; ++i) {
SCEVHandle H = getOperand(i)->replaceSymbolicValuesWithConcrete(Sym, Conc);
if (H != getOperand(i)) {
std::vector<SCEVHandle> NewOps;
NewOps.reserve(getNumOperands());
for (unsigned j = 0; j != i; ++j)
NewOps.push_back(getOperand(j));
NewOps.push_back(H);
for (++i; i != e; ++i)
NewOps.push_back(getOperand(i)->
replaceSymbolicValuesWithConcrete(Sym, Conc));
if (isa<SCEVAddExpr>(this))
return SCEVAddExpr::get(NewOps);
else if (isa<SCEVMulExpr>(this))
return SCEVMulExpr::get(NewOps);
else
assert(0 && "Unknown commutative expr!");
}
}
return this;
}
// SCEVUDivs - Only allow the creation of one SCEVUDivExpr for any particular
// input. Don't use a SCEVHandle here, or else the object will never be
// deleted!
@ -290,6 +323,28 @@ SCEVAddRecExpr::~SCEVAddRecExpr() {
Operands.end())));
}
SCEVHandle SCEVAddRecExpr::
replaceSymbolicValuesWithConcrete(const SCEVHandle &Sym,
const SCEVHandle &Conc) const {
for (unsigned i = 0, e = getNumOperands(); i != e; ++i) {
SCEVHandle H = getOperand(i)->replaceSymbolicValuesWithConcrete(Sym, Conc);
if (H != getOperand(i)) {
std::vector<SCEVHandle> NewOps;
NewOps.reserve(getNumOperands());
for (unsigned j = 0; j != i; ++j)
NewOps.push_back(getOperand(j));
NewOps.push_back(H);
for (++i; i != e; ++i)
NewOps.push_back(getOperand(i)->
replaceSymbolicValuesWithConcrete(Sym, Conc));
return get(NewOps, L);
}
}
return this;
}
bool SCEVAddRecExpr::isLoopInvariant(const Loop *QueryLoop) const {
// This recurrence is invariant w.r.t to QueryLoop iff QueryLoop doesn't
// contain L.
@ -1086,8 +1141,14 @@ namespace {
/// createNodeForPHI - Provide the special handling we need to analyze PHI
/// SCEVs.
SCEVHandle createNodeForPHI(PHINode *PN);
void UpdatePHIUserScalarEntries(Instruction *I, PHINode *PN,
std::set<Instruction*> &UpdatedInsts);
/// ReplaceSymbolicValueWithConcrete - This looks up the computed SCEV value
/// for the specified instruction and replaces any references to the
/// symbolic value SymName with the specified value. This is used during
/// PHI resolution.
void ReplaceSymbolicValueWithConcrete(Instruction *I,
const SCEVHandle &SymName,
const SCEVHandle &NewVal);
/// ComputeIterationCount - Compute the number of times the specified loop
/// will iterate.
@ -1153,26 +1214,27 @@ SCEVHandle ScalarEvolutionsImpl::getSCEV(Value *V) {
return S;
}
/// UpdatePHIUserScalarEntries - After PHI node analysis, we have a bunch of
/// entries in the scalar map that refer to the "symbolic" PHI value instead of
/// the recurrence value. After we resolve the PHI we must loop over all of the
/// using instructions that have scalar map entries and update them.
void ScalarEvolutionsImpl::UpdatePHIUserScalarEntries(Instruction *I,
PHINode *PN,
std::set<Instruction*> &UpdatedInsts) {
/// ReplaceSymbolicValueWithConcrete - This looks up the computed SCEV value for
/// the specified instruction and replaces any references to the symbolic value
/// SymName with the specified value. This is used during PHI resolution.
void ScalarEvolutionsImpl::
ReplaceSymbolicValueWithConcrete(Instruction *I, const SCEVHandle &SymName,
const SCEVHandle &NewVal) {
std::map<Value*, SCEVHandle>::iterator SI = Scalars.find(I);
if (SI == Scalars.end()) return; // This scalar wasn't previous processed.
if (UpdatedInsts.insert(I).second && !isa<PHINode>(PN)) {
Scalars.erase(SI); // Remove the old entry
getSCEV(I); // Calculate the new entry
for (Value::use_iterator UI = I->use_begin(), E = I->use_end();
UI != E; ++UI)
UpdatePHIUserScalarEntries(cast<Instruction>(*UI), PN, UpdatedInsts);
}
}
if (SI == Scalars.end()) return;
SCEVHandle NV =
SI->second->replaceSymbolicValuesWithConcrete(SymName, NewVal);
if (NV == SI->second) return; // No change.
SI->second = NV; // Update the scalars map!
// Any instruction values that use this instruction might also need to be
// updated!
for (Value::use_iterator UI = I->use_begin(), E = I->use_end();
UI != E; ++UI)
ReplaceSymbolicValueWithConcrete(cast<Instruction>(*UI), SymName, NewVal);
}
/// createNodeForPHI - PHI nodes have two cases. Either the PHI node exists in
/// a loop header, making it a potential recurrence, or it doesn't.
@ -1233,13 +1295,7 @@ SCEVHandle ScalarEvolutionsImpl::createNodeForPHI(PHINode *PN) {
// entries for the scalars that use the PHI (except for the PHI
// itself) to use the new analyzed value instead of the "symbolic"
// value.
Scalars.find(PN)->second = PHISCEV; // Update the PHI value
std::set<Instruction*> UpdatedInsts;
UpdatedInsts.insert(PN);
for (Value::use_iterator UI = PN->use_begin(), E = PN->use_end();
UI != E; ++UI)
UpdatePHIUserScalarEntries(cast<Instruction>(*UI), PN,
UpdatedInsts);
ReplaceSymbolicValueWithConcrete(PN, SymbolicName, PHISCEV);
return PHISCEV;
}
}