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author | Chris Lattner <sabre@nondot.org> | 2005-09-12 17:03:55 +0000 |
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committer | Chris Lattner <sabre@nondot.org> | 2005-09-12 17:03:55 +0000 |
commit | b6a69e70e00857a60861b584ed88cb57eae58175 (patch) | |
tree | 4938304265a5b1fb80c67ea00ec3878fd388bf6f /lib/Analysis/LoopInfo.cpp | |
parent | 331a1833e12b6229986f63f0a156062affbf3142 (diff) | |
download | external_llvm-b6a69e70e00857a60861b584ed88cb57eae58175.zip external_llvm-b6a69e70e00857a60861b584ed88cb57eae58175.tar.gz external_llvm-b6a69e70e00857a60861b584ed88cb57eae58175.tar.bz2 |
Add a new getLoopLatch() method.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@23315 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'lib/Analysis/LoopInfo.cpp')
-rw-r--r-- | lib/Analysis/LoopInfo.cpp | 26 |
1 files changed, 25 insertions, 1 deletions
diff --git a/lib/Analysis/LoopInfo.cpp b/lib/Analysis/LoopInfo.cpp index e12d317..b8315ac 100644 --- a/lib/Analysis/LoopInfo.cpp +++ b/lib/Analysis/LoopInfo.cpp @@ -373,12 +373,36 @@ BasicBlock *Loop::getLoopPreheader() const { if (SI != succ_end(Out)) return 0; // Multiple exits from the block, must not be a preheader. - // If there is exactly one preheader, return it. If there was zero, then Out // is still null. return Out; } +/// getLoopLatch - If there is a latch block for this loop, return it. A +/// latch block is the canonical backedge for a loop. A loop header in normal +/// form has two edges into it: one from a preheader and one from a latch +/// block. +BasicBlock *Loop::getLoopLatch() const { + BasicBlock *Header = getHeader(); + pred_iterator PI = pred_begin(Header), PE = pred_end(Header); + if (PI == PE) return 0; // no preds? + + BasicBlock *Latch = 0; + if (contains(*PI)) + Latch = *PI; + ++PI; + if (PI == PE) return 0; // only one pred? + + if (contains(*PI)) { + if (Latch) return 0; // multiple backedges + Latch = *PI; + } + ++PI; + if (PI != PE) return 0; // more than two preds + + return Latch; +} + /// getCanonicalInductionVariable - Check to see if the loop has a canonical /// induction variable: an integer recurrence that starts at 0 and increments by /// one each time through the loop. If so, return the phi node that corresponds |