diff options
Diffstat (limited to 'llvm/lib/Transforms/Scalar/IndVarSimplify.cpp')
| -rw-r--r-- | llvm/lib/Transforms/Scalar/IndVarSimplify.cpp | 16 |
1 files changed, 9 insertions, 7 deletions
diff --git a/llvm/lib/Transforms/Scalar/IndVarSimplify.cpp b/llvm/lib/Transforms/Scalar/IndVarSimplify.cpp index ecf0bef13df..333de75c244 100644 --- a/llvm/lib/Transforms/Scalar/IndVarSimplify.cpp +++ b/llvm/lib/Transforms/Scalar/IndVarSimplify.cpp @@ -728,11 +728,13 @@ bool IndVarSimplify::rewriteFirstIterationLoopExitValues(Loop *L) { IncomingValIdx != E; ++IncomingValIdx) { auto *IncomingBB = PN.getIncomingBlock(IncomingValIdx); - // We currently only support loop exits from loop header. If the - // incoming block is not loop header, we need to recursively check - // all conditions starting from loop header are loop invariants. - // Additional support might be added in the future. - if (IncomingBB != LoopHeader) + // Can we prove that the exit must run on the first iteration if it + // runs at all? (i.e. early exits are fine for our purposes, but + // traces which lead to this exit being taken on the 2nd iteration + // aren't.) Note that this is about whether the exit branch is + // executed, not about whether it is taken. + if (!L->getLoopLatch() || + !DT->dominates(IncomingBB, L->getLoopLatch())) continue; // Get condition that leads to the exit path. @@ -753,8 +755,8 @@ bool IndVarSimplify::rewriteFirstIterationLoopExitValues(Loop *L) { auto *ExitVal = dyn_cast<PHINode>(PN.getIncomingValue(IncomingValIdx)); - // Only deal with PHIs. - if (!ExitVal) + // Only deal with PHIs in the loop header. + if (!ExitVal || ExitVal->getParent() != L->getHeader()) continue; // If ExitVal is a PHI on the loop header, then we know its |
