Author: dpatel
Date: Fri Aug 24 00:36:56 2007
New Revision: 41356
URL: http://llvm.org/viewvc/llvm-project?rev=41356&view=rev
Log:
Tightenup loop filter.
Modified:
llvm/trunk/lib/Transforms/Scalar/LoopIndexSplit.cpp
Modified: llvm/trunk/lib/Transforms/Scalar/LoopIndexSplit.cpp
URL:
http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/LoopIndexSplit.cpp?rev=41356&r1=41355&r2=41356&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/LoopIndexSplit.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/LoopIndexSplit.cpp Fri Aug 24 00:36:56 2007
@@ -272,7 +272,12 @@
if (!ExitingBlock)
return;
-
+
+ // If exiting block is neither loop header nor loop latch then this loop is
+ // not suitable.
+ if (ExitingBlock != L->getHeader() && ExitingBlock != L->getLoopLatch())
+ return;
+
// If exit block's terminator is conditional branch inst then we have found
// exit condition.
BranchInst *BR = dyn_cast<BranchInst>(ExitingBlock->getTerminator());
@@ -705,7 +710,22 @@
if (Succ0 == *PI)
return false;
- return true;
+ // Finally this split condition is safe only if merge point for
+ // split condition branch is loop latch. This check along with previous
+ // check, to ensure that exit condition is in either loop latch or header,
+ // filters all loops with non-empty loop body between merge point
+ // and exit condition.
+ DominanceFrontier::iterator Succ0DF = DF->find(Succ0);
+ assert (Succ0DF != DF->end() && "Unable to find Succ0 dominance frontier");
+ if (Succ0DF->second.count(Latch))
+ return true;
+
+ DominanceFrontier::iterator Succ1DF = DF->find(Succ1);
+ assert (Succ1DF != DF->end() && "Unable to find Succ1 dominance frontier");
+ if (Succ1DF->second.count(Latch))
+ return true;
+
+ return false;
}
/// splitLoop - Split current loop L in two loops using split information
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