diff options
| -rw-r--r-- | src/mir/optimise.cpp | 49 |
1 files changed, 35 insertions, 14 deletions
diff --git a/src/mir/optimise.cpp b/src/mir/optimise.cpp index 2987cf39..aacd0b6e 100644 --- a/src/mir/optimise.cpp +++ b/src/mir/optimise.cpp @@ -1429,12 +1429,6 @@ bool MIR_Optimise_Inlining(::MIR::TypeResolve& state, ::MIR::Function& fcn, bool return inline_happened; } -// TODO: New pass that removes useless borrows -// ``` -// _$1 = & _$0; -// (*_$1).1 = 0x0; -// ``` - namespace { struct StmtRef { unsigned bb_idx; @@ -1447,13 +1441,20 @@ namespace { } // Iterates the path between two positions, NOT visiting entry specified by `end` - bool iter_path( + enum class IterPathRes { + Abort, + EarlyTrue, + Complete, + }; + IterPathRes iter_path( const ::MIR::Function& fcn, const StmtRef& start, const StmtRef& end, ::std::function<bool(StmtRef, const ::MIR::Statement&)> cb_stmt, ::std::function<bool(StmtRef, const ::MIR::Terminator&)> cb_term ) { - assert(start.bb_idx == end.bb_idx); // TODO: Support chaining. + if( start.bb_idx != end.bb_idx ) { // TODO: Support following Goto/Call + return IterPathRes::Abort; + } assert(start.stmt_idx <= end.stmt_idx); size_t bb_idx = start.bb_idx; @@ -1464,19 +1465,19 @@ namespace { { if( cb_stmt(ref, bb.statements.at(ref.stmt_idx)) ) { - return true; + return IterPathRes::EarlyTrue; } } else { if( cb_term(ref, bb.terminator) ) { - return true; + return IterPathRes::EarlyTrue; } break; } } - return false; + return IterPathRes::Complete; } ::std::function<bool(const ::MIR::LValue& , ValUsage)> check_invalidates_lvalue_cb(const ::MIR::LValue& val) @@ -1530,7 +1531,6 @@ bool MIR_Optimise_DeTemporary_SingleSetAndUse(::MIR::TypeResolve& state, ::MIR:: bool changed = false; TRACE_FUNCTION_FR("", changed); - // TODO: New algorithm // Find all single-use/single-write locals // - IF the usage is a RValue::Use, AND the usage destination is not invalidated between set/use // - Replace initialisation destination with usage destination (delete usage statement) @@ -1623,7 +1623,7 @@ bool MIR_Optimise_DeTemporary_SingleSetAndUse(::MIR::TypeResolve& state, ::MIR:: // - Iterate the path(s) between the two statements to check if the destination would be invalidated // > The iterate function doesn't (yet) support following BB chains, so assume invalidated if over a jump. - bool invalidated = (slot.set_loc.bb_idx != slot.use_loc.bb_idx) || iter_path(fcn, slot.set_loc, slot.use_loc, + bool invalidated = IterPathRes::Complete != iter_path(fcn, slot.set_loc, slot.use_loc, [&](auto loc, const auto& stmt)->bool{ return check_invalidates_lvalue(stmt, dst); }, [&](auto loc, const auto& term)->bool{ return check_invalidates_lvalue(term, dst); } ); @@ -1639,6 +1639,7 @@ bool MIR_Optimise_DeTemporary_SingleSetAndUse(::MIR::TypeResolve& state, ::MIR:: DEBUG("Move destination " << dst << " from " << use_bb.statements[slot.use_loc.stmt_idx] << " to " << set_stmt); se.dst = dst.clone(); use_bb.statements[slot.use_loc.stmt_idx] = ::MIR::Statement(); + changed = true; } TU_ARMA(Asm, se) { // Initialised from an ASM statement, find the variable in the output parameters @@ -1670,7 +1671,8 @@ bool MIR_Optimise_DeTemporary_SingleSetAndUse(::MIR::TypeResolve& state, ::MIR:: const auto& src = set_stmt.as_Assign().src.as_Use(); // Check if the source of initial assignment is invalidated in the meantime. - bool invalidated = (slot.set_loc.bb_idx != slot.use_loc.bb_idx) || iter_path(fcn, slot.set_loc, slot.use_loc, + // - TODO: We don't want to check the set statement, just all others after it + bool invalidated = IterPathRes::Complete != iter_path(fcn, slot.set_loc, slot.use_loc, [&](auto loc, const auto& stmt)->bool{ return check_invalidates_lvalue(stmt, src); }, [&](auto loc, const auto& term)->bool{ return check_invalidates_lvalue(term, src); } ); @@ -1705,6 +1707,7 @@ bool MIR_Optimise_DeTemporary_SingleSetAndUse(::MIR::TypeResolve& state, ::MIR:: else { set_stmt = ::MIR::Statement(); + changed = true; } } else @@ -1719,6 +1722,7 @@ bool MIR_Optimise_DeTemporary_SingleSetAndUse(::MIR::TypeResolve& state, ::MIR:: else { set_stmt = ::MIR::Statement(); + changed = true; } } } @@ -1730,6 +1734,7 @@ bool MIR_Optimise_DeTemporary_SingleSetAndUse(::MIR::TypeResolve& state, ::MIR:: } // TODO: If the source is a Borrow and the use is a Deref, then propagate forwards + // - This would be a simpler version of a var more compliciated algorithm DEBUG("Can't replace:"); if( slot.set_loc.stmt_idx < set_bb.statements.size() ) @@ -1754,6 +1759,22 @@ bool MIR_Optimise_DeTemporary_SingleSetAndUse(::MIR::TypeResolve& state, ::MIR:: return changed; } +// TODO: New pass that removes useless borrows +// ``` +// _$1 = & _$0; +// (*_$1).1 = 0x0; +// ``` +//bool MIR_Optimise_DeTemporary_Borrows(::MIR::TypeResolve& state, ::MIR::Function& fcn) +//{ +// bool changed = false; +// TRACE_FUNCTION_FR("", changed); +// +// // Find all single-assign borrows that are only ever used via Deref +// // - Direct drop is ignored for this purpose +// +// return changed; +//} + // -------------------------------------------------------------------- // Replaces uses of stack slots with what they were assigned with (when // possible) |