diff options
Diffstat (limited to 'lib/Transforms/Scalar')
-rw-r--r-- | lib/Transforms/Scalar/JumpThreading.cpp | 8 |
1 files changed, 7 insertions, 1 deletions
diff --git a/lib/Transforms/Scalar/JumpThreading.cpp b/lib/Transforms/Scalar/JumpThreading.cpp index e501ff29d0..6e50d3331d 100644 --- a/lib/Transforms/Scalar/JumpThreading.cpp +++ b/lib/Transforms/Scalar/JumpThreading.cpp @@ -158,7 +158,13 @@ bool JumpThreading::runOnFunction(Function &F) { TLI = &getAnalysis<TargetLibraryInfo>(); LVI = &getAnalysis<LazyValueInfo>(); - // Remove unreachable blocks from function as they may result in infinite loop. + // Remove unreachable blocks from function as they may result in infinite + // loop. We do threading if we found something profitable. Jump threading a + // branch can create other opportunities. If these opportunities form a cycle + // i.e. if any jump treading is undoing previous threading in the path, then + // we will loop forever. We take care of this issue by not jump threading for + // back edges. This works for normal cases but not for unreachable blocks as + // they may have cycle with no back edge. removeUnreachableBlocks(F); FindLoopHeaders(F); |