shader_recompiler/dead_code_elimination: Add DeadBranchElimination pass
This adds a pass to eliminate if(false) branches within the shader code
This commit is contained in:
parent
75046a3351
commit
f10d40a0a2
1 changed files with 62 additions and 9 deletions
|
@ -7,19 +7,72 @@
|
||||||
#include "shader_recompiler/ir_opt/passes.h"
|
#include "shader_recompiler/ir_opt/passes.h"
|
||||||
|
|
||||||
namespace Shader::Optimization {
|
namespace Shader::Optimization {
|
||||||
|
namespace {
|
||||||
void DeadCodeEliminationPass(IR::Program& program) {
|
template <bool TEST_USES>
|
||||||
|
void DeadInstElimination(IR::Block* const block) {
|
||||||
// We iterate over the instructions in reverse order.
|
// We iterate over the instructions in reverse order.
|
||||||
// This is because removing an instruction reduces the number of uses for earlier instructions.
|
// This is because removing an instruction reduces the number of uses for earlier instructions.
|
||||||
for (IR::Block* const block : program.post_order_blocks) {
|
auto it{block->end()};
|
||||||
auto it{block->end()};
|
while (it != block->begin()) {
|
||||||
while (it != block->begin()) {
|
--it;
|
||||||
--it;
|
if constexpr (TEST_USES) {
|
||||||
if (!it->HasUses() && !it->MayHaveSideEffects()) {
|
if (it->HasUses() || it->MayHaveSideEffects()) {
|
||||||
it->Invalidate();
|
continue;
|
||||||
it = block->Instructions().erase(it);
|
|
||||||
}
|
}
|
||||||
}
|
}
|
||||||
|
it->Invalidate();
|
||||||
|
it = block->Instructions().erase(it);
|
||||||
|
}
|
||||||
|
}
|
||||||
|
|
||||||
|
void DeadBranchElimination(IR::Program& program) {
|
||||||
|
const auto begin_it{program.syntax_list.begin()};
|
||||||
|
for (auto node_it = begin_it; node_it != program.syntax_list.end(); ++node_it) {
|
||||||
|
if (node_it->type != IR::AbstractSyntaxNode::Type::If) {
|
||||||
|
continue;
|
||||||
|
}
|
||||||
|
IR::Inst* const cond_ref{node_it->data.if_node.cond.Inst()};
|
||||||
|
const IR::U1 cond{cond_ref->Arg(0)};
|
||||||
|
if (!cond.IsImmediate()) {
|
||||||
|
continue;
|
||||||
|
}
|
||||||
|
if (cond.U1()) {
|
||||||
|
continue;
|
||||||
|
}
|
||||||
|
// False immediate condition. Remove condition ref, erase the entire branch.
|
||||||
|
cond_ref->Invalidate();
|
||||||
|
// Account for nested if-statements within the if(false) branch
|
||||||
|
u32 nested_ifs{1u};
|
||||||
|
while (node_it->type != IR::AbstractSyntaxNode::Type::EndIf || nested_ifs > 0) {
|
||||||
|
node_it = program.syntax_list.erase(node_it);
|
||||||
|
switch (node_it->type) {
|
||||||
|
case IR::AbstractSyntaxNode::Type::If:
|
||||||
|
++nested_ifs;
|
||||||
|
break;
|
||||||
|
case IR::AbstractSyntaxNode::Type::EndIf:
|
||||||
|
--nested_ifs;
|
||||||
|
break;
|
||||||
|
case IR::AbstractSyntaxNode::Type::Block: {
|
||||||
|
IR::Block* const block{node_it->data.block};
|
||||||
|
DeadInstElimination<false>(block);
|
||||||
|
break;
|
||||||
|
}
|
||||||
|
default:
|
||||||
|
break;
|
||||||
|
}
|
||||||
|
}
|
||||||
|
// Erase EndIf node of the if(false) branch
|
||||||
|
node_it = program.syntax_list.erase(node_it);
|
||||||
|
// Account for loop increment
|
||||||
|
--node_it;
|
||||||
|
}
|
||||||
|
}
|
||||||
|
} // namespace
|
||||||
|
|
||||||
|
void DeadCodeEliminationPass(IR::Program& program) {
|
||||||
|
DeadBranchElimination(program);
|
||||||
|
for (IR::Block* const block : program.post_order_blocks) {
|
||||||
|
DeadInstElimination<true>(block);
|
||||||
}
|
}
|
||||||
}
|
}
|
||||||
|
|
||||||
|
|
Loading…
Reference in a new issue