diff options
Diffstat (limited to 'contrib/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp')
| -rw-r--r-- | contrib/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp | 19 |
1 files changed, 18 insertions, 1 deletions
diff --git a/contrib/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp b/contrib/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp index d57ec22..b085b00 100644 --- a/contrib/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp +++ b/contrib/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp @@ -77,6 +77,12 @@ #include <algorithm> using namespace llvm; +/// MaxIVUsers is an arbitrary threshold that provides an early opportunitiy for +/// bail out. This threshold is far beyond the number of users that LSR can +/// conceivably solve, so it should not affect generated code, but catches the +/// worst cases before LSR burns too much compile time and stack space. +static const unsigned MaxIVUsers = 200; + // Temporary flag to cleanup congruent phis after LSR phi expansion. // It's currently disabled until we can determine whether it's truly useful or // not. The flag should be removed after the v3.0 release. @@ -4102,7 +4108,7 @@ LSRInstance::HoistInsertPosition(BasicBlock::iterator IP, // Attempt to find an insert position in the middle of the block, // instead of at the end, so that it can be used for other expansions. if (IDom == Inst->getParent() && - (!BetterPos || DT.dominates(BetterPos, Inst))) + (!BetterPos || !DT.dominates(Inst, BetterPos))) BetterPos = llvm::next(BasicBlock::iterator(Inst)); } if (!AllDominate) @@ -4519,6 +4525,17 @@ LSRInstance::LSRInstance(const TargetLowering *tli, Loop *l, Pass *P) // If there's no interesting work to be done, bail early. if (IU.empty()) return; + // If there's too much analysis to be done, bail early. We won't be able to + // model the problem anyway. + unsigned NumUsers = 0; + for (IVUsers::const_iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI) { + if (++NumUsers > MaxIVUsers) { + DEBUG(dbgs() << "LSR skipping loop, too many IV Users in " << *L + << "\n"); + return; + } + } + #ifndef NDEBUG // All dominating loops must have preheaders, or SCEVExpander may not be able // to materialize an AddRecExpr whose Start is an outer AddRecExpr. |
