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/*
* MRustC - Rust Compiler
* - By John Hodge (Mutabah/thePowersGang)
*
* mir/optimise.cpp
* - MIR Optimisations
*
*/
#include "main_bindings.hpp"
#include "mir.hpp"
#include <hir/visitor.hpp>
#include <hir_typeck/static.hpp>
#include <mir/helpers.hpp>
#include <mir/operations.hpp>
namespace {
::MIR::BasicBlockId get_new_target(const ::MIR::TypeResolve& state, ::MIR::BasicBlockId bb)
{
const auto& target = state.get_block(bb);
if( target.statements.size() != 0 )
{
return bb;
}
else if( !target.terminator.is_Goto() )
{
return bb;
}
else
{
// Make sure we don't infinite loop
if( bb == target.terminator.as_Goto() )
return bb;
auto rv = get_new_target(state, target.terminator.as_Goto());
DEBUG(bb << " => " << rv);
return rv;
}
}
}
void MIR_Optimise(const StaticTraitResolve& resolve, const ::HIR::ItemPath& path, ::MIR::Function& fcn, const ::HIR::Function::args_t& args, const ::HIR::TypeRef& ret_type)
{
static Span sp;
TRACE_FUNCTION_F(path);
::MIR::TypeResolve state { sp, resolve, FMT_CB(ss, ss << path;), ret_type, args, fcn };
// 1. Replace targets that point to a block that is just a goto
for(auto& block : fcn.blocks)
{
TU_MATCHA( (block.terminator), (e),
(Incomplete,
),
(Return,
),
(Diverge,
),
(Goto,
e = get_new_target(state, e);
),
(Panic,
),
(If,
e.bb0 = get_new_target(state, e.bb0);
e.bb1 = get_new_target(state, e.bb1);
),
(Switch,
for(auto& target : e.targets)
target = get_new_target(state, target);
),
(Call,
e.ret_block = get_new_target(state, e.ret_block);
e.panic_block = get_new_target(state, e.panic_block);
)
)
}
#if 0
// GC pass on blocks and variables
// - Find unused blocks, then delete and rewrite all references.
{
::std::vector<bool> visited( fcn.blocks.size() );
::std::vector< ::MIR::BasicBlockId> to_visit;
to_visit.push_back( 0 );
while( to_visit.size() > 0 )
{
auto bb = to_visit.back(); to_visit.pop_back();
visited[bb] = true;
const auto& block = fcn.blocks[bb];
TU_MATCHA( (block.terminator), (e),
(Incomplete,
),
(Return,
),
(Diverge,
),
(Goto,
if( !visited[e] )
to_visit.push_back(e);
),
(Panic,
),
(If,
if( !visited[e.bb0] )
to_visit.push_back(e.bb0);
if( !visited[e.bb1] )
to_visit.push_back(e.bb1);
),
(Switch,
for(auto& target : e.targets)
if( !visited[target] )
to_visit.push_back(target);
),
(Call,
if( !visited[e.ret_block] )
to_visit.push_back(e.ret_block);
if( !visited[e.panic_block] )
to_visit.push_back(e.panic_block);
)
)
}
::std::vector<unsigned int> rewrite_table;
for(unsigned int i = 0, j = 0; i < fcn.blocks.size(); i ++)
{
if( visited[i] ) {
rewrite_table.push_back(j++);
}
else {
rewrite_table.push_back(~0u);
}
}
auto it = fcn.blocks.begin();
for(unsigned int i = 0; i < visited.size(); i ++)
{
if( !visited[i] )
{
// Delete
DEBUG("GC bb" << i);
it = fcn.blocks.erase(it);
}
else
{
// Rewrite and advance
TU_MATCHA( (it->terminator), (e),
(Incomplete,
),
(Return,
),
(Diverge,
),
(Goto,
e = rewrite_table[e];
),
(Panic,
),
(If,
e.bb0 = rewrite_table[e.bb0];
e.bb1 = rewrite_table[e.bb1];
),
(Switch,
for(auto& target : e.targets)
target = rewrite_table[target];
),
(Call,
e.ret_block = rewrite_table[e.ret_block];
e.panic_block = rewrite_table[e.panic_block];
)
)
++it;
}
}
}
#endif
}
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