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Move Rewriter.clear() earlier, to avoid triggerring the AssertingVH by 

one of the RecursivelyDeleteTriviallyDeadInstructions.
Add a comment explaining why the cache needs to be cleared.

llvm-svn: 72372
This commit is contained in:
Torok Edwin 2009-05-24 20:08:21 +00:00
parent 5349cf5f4b
commit 26895b518b
1 changed files with 8 additions and 2 deletions
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10
llvm/lib/Transforms/Scalar/IndVarSimplify.cpp
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@ -414,9 +414,12 @@ bool IndVarSimplify::runOnLoop(Loop *L, LPPassManager &LPM) {
Rewriter.setInsertionPoint(Header->getFirstNonPHI()); Rewriter.setInsertionPoint(Header->getFirstNonPHI());
// Rewrite IV-derived expressions. // Rewrite IV-derived expressions. Clears the rewriter cache.
RewriteIVExpressions(L, LargestType, Rewriter); RewriteIVExpressions(L, LargestType, Rewriter);
// The Rewriter may only be used for isInsertedInstruction queries from this
// point on.
// Loop-invariant instructions in the preheader that aren't used in the // Loop-invariant instructions in the preheader that aren't used in the
// loop may be sunk below the loop to reduce register pressure. // loop may be sunk below the loop to reduce register pressure.
SinkUnusedInvariants(L, Rewriter); SinkUnusedInvariants(L, Rewriter);
@ -424,7 +427,6 @@ bool IndVarSimplify::runOnLoop(Loop *L, LPPassManager &LPM) {
// Reorder instructions to avoid use-before-def conditions. // Reorder instructions to avoid use-before-def conditions.
FixUsesBeforeDefs(L, Rewriter); FixUsesBeforeDefs(L, Rewriter);
Rewriter.clear();
// For completeness, inform IVUsers of the IV use in the newly-created // For completeness, inform IVUsers of the IV use in the newly-created
// loop exit test instruction. // loop exit test instruction.
if (NewICmp) if (NewICmp)
@ -574,6 +576,10 @@ void IndVarSimplify::RewriteIVExpressions(Loop *L, const Type *LargestType,
} }
} }
// Clear the rewriter cache, because values that are in the rewriter's cache
// can be deleted in the loop below, causing the AssertingVH in the cache to
// trigger.
Rewriter.clear();
// Now that we're done iterating through lists, clean up any instructions // Now that we're done iterating through lists, clean up any instructions
// which are now dead. // which are now dead.
while (!DeadInsts.empty()) { while (!DeadInsts.empty()) {