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Fix SCEVExpander's existing PHI reuse checking to recognize the

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case where there are loop-invariant instructions somehow left
inside the loop, and in a position where they won't dominate
the IV increment position.

llvm-svn: 96448
This commit is contained in:
Dan Gohman 2010-02-17 02:39:31 +00:00
parent 0f421b8fc5
commit 1cc421b590
1 changed files with 13 additions and 0 deletions
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13
lib/Analysis/ScalarEvolutionExpander.cpp
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@ -658,6 +658,19 @@ SCEVExpander::getAddRecExprPHILiterally(const SCEVAddRecExpr *Normalized,
IncV = 0;
break;
}
// If any of the operands don't dominate the insert position, bail.
// Addrec operands are always loop-invariant, so this can only happen
// if there are instructions which haven't been hoisted.
for (User::op_iterator OI = IncV->op_begin()+1,
OE = IncV->op_end(); OI != OE; ++OI)
if (Instruction *OInst = dyn_cast<Instruction>(OI))
if (!SE.DT->dominates(OInst, IVIncInsertPos)) {
IncV = 0;
break;
}
if (!IncV)
break;
// Advance to the next instruction.
IncV = dyn_cast<Instruction>(IncV->getOperand(0));
if (!IncV)
break;