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Avoid exponential growth of a table. It feels like

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there should be a better way to do this.  PR 8679.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@120457 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dale Johannesen 2010-11-30 20:23:21 +00:00
parent c7373f8158
commit f619b5a665
1 changed files with 22 additions and 5 deletions
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27
lib/Transforms/Scalar/SCCP.cpp
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@ -481,6 +481,23 @@ private:
}
}
/// InsertInOverdefinedPHIs - Insert an entry in the UsersOfOverdefinedPHIS
/// map for I and PN, but if one is there already, do not create another.
/// (Duplicate entries do not break anything directly, but can lead to
/// exponential growth of the table in rare cases.)
void InsertInOverdefinedPHIs(Instruction *I, PHINode *PN) {
std::multimap<PHINode*, Instruction*>::iterator J, E;
bool found = false;
tie(J, E) = UsersOfOverdefinedPHIs.equal_range(PN);
for (; J != E; ++J)
if (J->second == I) {
found = true;
break;
}
if (!found)
UsersOfOverdefinedPHIs.insert(std::make_pair(PN, I));
}
private:
friend class InstVisitor<SCCPSolver>;
@ -973,9 +990,9 @@ void SCCPSolver::visitBinaryOperator(Instruction &I) {
if (Result.isConstant()) {
markConstant(IV, &I, Result.getConstant());
// Remember that this instruction is virtually using the PHI node
// operands.
UsersOfOverdefinedPHIs.insert(std::make_pair(PN1, &I));
UsersOfOverdefinedPHIs.insert(std::make_pair(PN2, &I));
// operands.
InsertInOverdefinedPHIs(&I, PN1);
InsertInOverdefinedPHIs(&I, PN2);
return;
}
@ -1056,8 +1073,8 @@ void SCCPSolver::visitCmpInst(CmpInst &I) {
markConstant(&I, Result.getConstant());
// Remember that this instruction is virtually using the PHI node
// operands.
UsersOfOverdefinedPHIs.insert(std::make_pair(PN1, &I));
UsersOfOverdefinedPHIs.insert(std::make_pair(PN2, &I));
InsertInOverdefinedPHIs(&I, PN1);
InsertInOverdefinedPHIs(&I, PN2);
return;
}