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Fix an oversight in isPotentiallyReachable where we wouldn't do any CFG-walking

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to find loops if the From and To instructions were in the same block.

Refactor the code a little now that we need to fill to start the CFG-walking
algorithm with more than one starting basic block sometimes.

Special thanks to Andrew Trick for catching an error in my understanding of
natural loops in code review.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@188236 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Nick Lewycky
2013-08-13 00:03:47 +00:00
parent b58bddf258
commit 72dba254ae
3 changed files with 99 additions and 53 deletions
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12
include/llvm/Analysis/CFG.h
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@ -49,6 +49,9 @@ unsigned GetSuccessorNumber(BasicBlock *BB, BasicBlock *Succ);
bool isCriticalEdge(const TerminatorInst *TI, unsigned SuccNum,
bool AllowIdenticalEdges = false);
/// \brief Determine whether instruction 'To' is reachable from 'From',
/// returning true if uncertain.
///
/// Determine whether there is a path from From to To within a single function.
/// Returns false only if we can prove that once 'From' has been executed then
/// 'To' can not be executed. Conservatively returns true.
@ -64,6 +67,15 @@ bool isCriticalEdge(const TerminatorInst *TI, unsigned SuccNum,
bool isPotentiallyReachable(const Instruction *From, const Instruction *To,
DominatorTree *DT = 0, LoopInfo *LI = 0);
/// \brief Determine whether block 'To' is reachable from 'From', returning
/// true if uncertain.
///
/// Determine whether there is a path from From to To within a single function.
/// Returns false only if we can prove that once 'From' has been reached then
/// 'To' can not be executed. Conservatively returns true.
bool isPotentiallyReachable(const BasicBlock *From, const BasicBlock *To,
DominatorTree *DT = 0, LoopInfo *LI = 0);
} // End llvm namespace
#endif