diff options
Diffstat (limited to 'src/mir/optimise.cpp')
| -rw-r--r-- | src/mir/optimise.cpp | 70 |
1 files changed, 70 insertions, 0 deletions
diff --git a/src/mir/optimise.cpp b/src/mir/optimise.cpp index 9935454e..4c2da555 100644 --- a/src/mir/optimise.cpp +++ b/src/mir/optimise.cpp @@ -498,6 +498,7 @@ bool MIR_Optimise_PropagateSingleAssignments(::MIR::TypeResolve& state, ::MIR::F bool MIR_Optimise_PropagateKnownValues(::MIR::TypeResolve& state, ::MIR::Function& fcn); bool MIR_Optimise_DeTemporary(::MIR::TypeResolve& state, ::MIR::Function& fcn); // Eliminate useless temporaries bool MIR_Optimise_UnifyTemporaries(::MIR::TypeResolve& state, ::MIR::Function& fcn); +bool MIR_Optimise_CommonStatements(::MIR::TypeResolve& state, ::MIR::Function& fcn); bool MIR_Optimise_UnifyBlocks(::MIR::TypeResolve& state, ::MIR::Function& fcn); bool MIR_Optimise_ConstPropagte(::MIR::TypeResolve& state, ::MIR::Function& fcn); bool MIR_Optimise_DeadDropFlags(::MIR::TypeResolve& state, ::MIR::Function& fcn); @@ -600,6 +601,9 @@ void MIR_Optimise(const StaticTraitResolve& resolve, const ::HIR::ItemPath& path } #endif + // >> Move common statements (assignments) across gotos. + change_happened |= MIR_Optimise_CommonStatements(state, fcn); + // >> Combine Duplicate Blocks change_happened |= MIR_Optimise_UnifyBlocks(state, fcn); // >> Remove assignments of unsed drop flags @@ -1431,6 +1435,72 @@ bool MIR_Optimise_DeTemporary(::MIR::TypeResolve& state, ::MIR::Function& fcn) return changed; } + +// -------------------------------------------------------------------- +// Detect common statements between all source arms of a block +// -------------------------------------------------------------------- +bool MIR_Optimise_CommonStatements(::MIR::TypeResolve& state, ::MIR::Function& fcn) +{ + bool changed = false; + TRACE_FUNCTION_FR("", changed); + + for(size_t bb_idx = 0; bb_idx < fcn.blocks.size(); bb_idx ++) + { + state.set_cur_stmt(bb_idx, 0); + + bool skip = false; + ::std::vector<size_t> sources; + // Find source blocks + for(size_t bb2_idx = 0; bb2_idx < fcn.blocks.size(); bb2_idx ++) + { + const auto& blk = fcn.blocks[bb2_idx]; + // TODO: Handle non-Goto branches? (e.g. calls) + if( blk.terminator.is_Goto() && blk.terminator.as_Goto() == bb_idx ) + { + if( blk.statements.empty() ) + { + DEBUG(state << " BB" << bb2_idx << " empty"); + skip = true; + break ; + } + if( !sources.empty() ) + { + if( blk.statements.back() != fcn.blocks[sources.front()].statements.back() ) + { + DEBUG(state << " BB" << bb2_idx << " doesn't end with " << fcn.blocks[sources.front()].statements.back() << " instead " << blk.statements.back()); + skip = true; + break; + } + } + sources.push_back(bb2_idx); + } + else + { + visit_terminator_target(blk.terminator, [&](const auto& dst_idx) { + if( dst_idx == bb_idx ) { + DEBUG(state << " BB" << bb2_idx << " doesn't end Goto - instead " << blk.terminator); + skip = true; + } + }); + } + } + + if( !skip && sources.size() > 1 ) + { + // Found a common assignment, add to the start and remove from sources. + auto stmt = ::std::move(fcn.blocks[sources.front()].statements.back()); + MIR_DEBUG(state, "Move common final statements from " << sources << " to " << bb_idx << " - " << stmt); + for(auto idx : sources) + { + fcn.blocks[idx].statements.pop_back(); + } + fcn.blocks[bb_idx].statements.insert(fcn.blocks[bb_idx].statements.begin(), ::std::move(stmt)); + } + } + return changed; +} + + // -------------------------------------------------------------------- // If two temporaries don't overlap in lifetime (blocks in which they're valid), unify the two // -------------------------------------------------------------------- |