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Fix pathological complexity explosion for certain shaders. #1594

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Jan 15, 2021
Merged

Fix pathological complexity explosion for certain shaders. #1594

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16 changes: 12 additions & 4 deletions spirv_cross.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -2829,7 +2829,8 @@ const SPIRConstant &Compiler::get_constant(ConstantID id) const
return get<SPIRConstant>(id);
}

static bool exists_unaccessed_path_to_return(const CFG &cfg, uint32_t block, const unordered_set<uint32_t> &blocks)
static bool exists_unaccessed_path_to_return(const CFG &cfg, uint32_t block, const unordered_set<uint32_t> &blocks,
unordered_set<uint32_t> &visit_cache)
{
// This block accesses the variable.
if (blocks.find(block) != end(blocks))
Expand All @@ -2841,8 +2842,14 @@ static bool exists_unaccessed_path_to_return(const CFG &cfg, uint32_t block, con

// If any of our successors have a path to the end, there exists a path from block.
for (auto &succ : cfg.get_succeeding_edges(block))
if (exists_unaccessed_path_to_return(cfg, succ, blocks))
return true;
{
if (visit_cache.count(succ) == 0)
{
if (exists_unaccessed_path_to_return(cfg, succ, blocks, visit_cache))
return true;
visit_cache.insert(succ);
}
}

return false;
}
Expand Down Expand Up @@ -2899,7 +2906,8 @@ void Compiler::analyze_parameter_preservation(
// void foo(int &var) { if (cond) var = 10; }
// Using read/write counts, we will think it's just an out variable, but it really needs to be inout,
// because if we don't write anything whatever we put into the function must return back to the caller.
if (exists_unaccessed_path_to_return(cfg, entry.entry_block, itr->second))
unordered_set<uint32_t> visit_cache;
if (exists_unaccessed_path_to_return(cfg, entry.entry_block, itr->second, visit_cache))
arg.read_count++;
}
}
Expand Down