http://llvm.org/bugs/show_bug.cgi?id=14794
Bug #: 14794
Summary: Request a conservative reachability analysis for
CapturesBefore
Product: libraries
Version: trunk
Platform: PC
OS/Version: All
Status: NEW
Severity: enhancement
Priority: P
Component: Global Analyses
AssignedTo: [email protected]
ReportedBy: [email protected]
CC: [email protected]
Classification: Unclassified
More discussions at
http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20121224/160534.html
We currently have a simple helper function (r=171512)
+ // Conservatively return true. Return false, if there is a single path
+ // starting from "From" and the path does not reach "To".
+ static bool hasPath(const BasicBlock *From, const BasicBlock *To) {
+ const unsigned MaxCheck = 5;
+ const BasicBlock *Current = From;
+ for (unsigned I = 0; I < MaxCheck; I++) {
+ unsigned NumSuccs = Current->getTerminator()->getNumSuccessors();
+ if (NumSuccs > 1)
+ return true;
+ if (NumSuccs == 0)
+ return false;
+ Current = Current->getTerminator()->getSuccessor(0);
+ if (Current == To)
+ return true;
+ }
+ return true;
+ }
This is too conservative, for performance, we should try to improve the
accuracy.
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