diff options
Diffstat (limited to 'src/mir/optimise.cpp')
| -rw-r--r-- | src/mir/optimise.cpp | 102 |
1 files changed, 55 insertions, 47 deletions
diff --git a/src/mir/optimise.cpp b/src/mir/optimise.cpp index f5a4236f..7f6cfce1 100644 --- a/src/mir/optimise.cpp +++ b/src/mir/optimise.cpp @@ -368,11 +368,65 @@ void MIR_Optimise(const StaticTraitResolve& resolve, const ::HIR::ItemPath& path // - Any lvalues in the source lvalue must not be mutated between the source assignment and the usage. // > This includes mutation, borrowing, or moving. { - ::std::map< unsigned int, ::MIR::LValue> replacements; + // 1. Function returns (reverse propagate) for(auto& block : fcn.blocks) { if( block.terminator.tag() == ::MIR::Terminator::TAGDEAD ) continue ; + + // If the terminator is a call that writes to a 1:1 value, replace the destination value with the eventual destination (if that value isn't used in the meantime) + if( block.terminator.is_Call() ) + { + // TODO: What if the destination located here is a 1:1 and its usage is listed to be replaced by the return value. + auto& e = block.terminator.as_Call(); + // TODO: Support variables too? + if( !e.ret_val.is_Temporary() ) + continue ; + const auto& vu = val_uses.tmp_uses[e.ret_val.as_Temporary().idx]; + if( !( vu.read == 1 && vu.write == 1 ) ) + continue ; + + // Iterate the target block, looking for where this value is used. + const ::MIR::LValue* new_dst = nullptr; + auto& blk2 = fcn.blocks.at(e.ret_block); + for(const auto& stmt : blk2.statements) + { + if( stmt.is_Assign() && stmt.as_Assign().src.is_Use() && stmt.as_Assign().src.as_Use() == e.ret_val ) { + new_dst = &stmt.as_Assign().dst; + break; + } + } + + // Ensure that the new destination value isn't used before assignment + if( new_dst ) + { + auto lvalue_impacts_dst = [&](const ::MIR::LValue& lv) { + return visit_mir_lvalue(*new_dst, true, [&](const auto& slv, bool ) { return lv == slv; }); + }; + for(auto it = blk2.statements.begin(); it != blk2.statements.end(); ++ it) + { + const auto& stmt = *it; + if( stmt.is_Assign() && stmt.as_Assign().src.is_Use() && stmt.as_Assign().src.as_Use() == e.ret_val ) + { + DEBUG("- Replace function return " << e.ret_val << " with " << *new_dst); + e.ret_val = new_dst->clone(); + it = blk2.statements.erase(it); + break; + } + if( visit_mir_lvalues(stmt, [&](const auto& lv, bool is_write){ return lv == *new_dst || (is_write && lvalue_impacts_dst(lv)); }) ) + { + break; + } + } + } + } + } + // 2. Assignments (forward propagate) + ::std::map< unsigned int, ::MIR::LValue> replacements; + for(const auto& block : fcn.blocks) + { + if( block.terminator.tag() == ::MIR::Terminator::TAGDEAD ) + continue ; //FOREACH_IDX(stmt_idx, block.statements) for(unsigned int stmt_idx = 0; stmt_idx < block.statements.size(); stmt_idx ++) { @@ -488,52 +542,6 @@ void MIR_Optimise(const StaticTraitResolve& resolve, const ::HIR::ItemPath& path DEBUG("- Single-write/read " << e.dst << " not replaced - couldn't find usage"); } } // for(stmt : block.statements) - - // If the terminator is a call that writes to a 1:1 value, replace the destination value with the eventual destination (if that value isn't used in the meantime) - if( block.terminator.is_Call() ) - { - auto& e = block.terminator.as_Call(); - // TODO: Support variables too? - if( !e.ret_val.is_Temporary() ) - continue ; - const auto& vu = val_uses.tmp_uses[e.ret_val.as_Temporary().idx]; - if( !( vu.read == 1 && vu.write == 1 ) ) - continue ; - - // Iterate the target block, looking for where this value is used. - const ::MIR::LValue* new_dst = nullptr; - auto& blk2 = fcn.blocks.at(e.ret_block); - for(const auto& stmt : blk2.statements) - { - if( stmt.is_Assign() && stmt.as_Assign().src.is_Use() && stmt.as_Assign().src.as_Use() == e.ret_val ) { - new_dst = &stmt.as_Assign().dst; - break; - } - } - - // Ensure that the new destination value isn't used before assignment - if( new_dst ) - { - auto lvalue_impacts_dst = [&](const ::MIR::LValue& lv) { - return visit_mir_lvalue(*new_dst, true, [&](const auto& slv, bool ) { return lv == slv; }); - }; - for(auto it = blk2.statements.begin(); it != blk2.statements.end(); ++ it) - { - const auto& stmt = *it; - if( stmt.is_Assign() && stmt.as_Assign().src.is_Use() && stmt.as_Assign().src.as_Use() == e.ret_val ) - { - DEBUG("- Replace function return " << e.ret_val << " with " << *new_dst); - e.ret_val = new_dst->clone(); - it = blk2.statements.erase(it); - break; - } - if( visit_mir_lvalues(stmt, [&](const auto& lv, bool is_write){ return lv == *new_dst || (is_write && lvalue_impacts_dst(lv)); }) ) - { - break; - } - } - } - } } for(;;) |