diff options
Diffstat (limited to 'llvm/lib/Analysis')
| -rw-r--r-- | llvm/lib/Analysis/IPA/InlineCost.cpp | 26 |
1 files changed, 23 insertions, 3 deletions
diff --git a/llvm/lib/Analysis/IPA/InlineCost.cpp b/llvm/lib/Analysis/IPA/InlineCost.cpp index c43b5ca2506..358f61fd523 100644 --- a/llvm/lib/Analysis/IPA/InlineCost.cpp +++ b/llvm/lib/Analysis/IPA/InlineCost.cpp @@ -808,9 +808,29 @@ bool CallAnalyzer::visitBranchInst(BranchInst &BI) { bool CallAnalyzer::visitSwitchInst(SwitchInst &SI) { // We model unconditional switches as free, see the comments on handling // branches. - return isa<ConstantInt>(SI.getCondition()) || - dyn_cast_or_null<ConstantInt>( - SimplifiedValues.lookup(SI.getCondition())); + if (isa<ConstantInt>(SI.getCondition())) + return true; + if (Value *V = SimplifiedValues.lookup(SI.getCondition())) + if (isa<ConstantInt>(V)) + return true; + + // Otherwise, we need to accumulate a cost proportional to the number of + // distinct successor blocks. This fan-out in the CFG cannot be represented + // for free even if we can represent the core switch as a jumptable that + // takes a single instruction. + // + // NB: We convert large switches which are just used to initialize large phi + // nodes to lookup tables instead in simplify-cfg, so this shouldn't prevent + // inlining those. It will prevent inlining in cases where the optimization + // does not (yet) fire. + SmallPtrSet<BasicBlock *, 8> SuccessorBlocks; + SuccessorBlocks.insert(SI.getDefaultDest()); + for (auto I = SI.case_begin(), E = SI.case_end(); I != E; ++I) + SuccessorBlocks.insert(I.getCaseSuccessor()); + // Add cost corresponding to the number of distinct destinations. The first + // we model as free because of fallthrough. + Cost += (SuccessorBlocks.size() - 1) * InlineConstants::InstrCost; + return false; } bool CallAnalyzer::visitIndirectBrInst(IndirectBrInst &IBI) { |
