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authorameerj <52414509+ameerj@users.noreply.github.com>2022-03-22 23:34:31 +0100
committerameerj <52414509+ameerj@users.noreply.github.com>2022-03-23 22:57:22 +0100
commit67159e3be76cf468288ae492ea22fc43a77a9d1e (patch)
tree1430335870a66823463f56f86cd98de6f8d5c6d8 /src
parentshader_recompiler/dead_code_elimination: Add DeadBranchElimination pass (diff)
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Diffstat (limited to 'src')
-rw-r--r--src/shader_recompiler/frontend/ir/microinstruction.cpp5
-rw-r--r--src/shader_recompiler/frontend/ir/value.h4
-rw-r--r--src/shader_recompiler/ir_opt/dead_code_elimination_pass.cpp27
3 files changed, 36 insertions, 0 deletions
diff --git a/src/shader_recompiler/frontend/ir/microinstruction.cpp b/src/shader_recompiler/frontend/ir/microinstruction.cpp
index 631446cf7..4a2564f47 100644
--- a/src/shader_recompiler/frontend/ir/microinstruction.cpp
+++ b/src/shader_recompiler/frontend/ir/microinstruction.cpp
@@ -326,6 +326,11 @@ void Inst::AddPhiOperand(Block* predecessor, const Value& value) {
phi_args.emplace_back(predecessor, value);
}
+void Inst::ErasePhiOperand(size_t index) {
+ const auto operand_it{phi_args.begin() + static_cast<ptrdiff_t>(index)};
+ phi_args.erase(operand_it);
+}
+
void Inst::OrderPhiArgs() {
if (op != Opcode::Phi) {
throw LogicError("{} is not a Phi instruction", op);
diff --git a/src/shader_recompiler/frontend/ir/value.h b/src/shader_recompiler/frontend/ir/value.h
index 947579852..14f6e55bc 100644
--- a/src/shader_recompiler/frontend/ir/value.h
+++ b/src/shader_recompiler/frontend/ir/value.h
@@ -179,9 +179,13 @@ public:
/// Get a pointer to the block of a phi argument.
[[nodiscard]] Block* PhiBlock(size_t index) const;
+
/// Add phi operand to a phi instruction.
void AddPhiOperand(Block* predecessor, const Value& value);
+ // Erase the phi operand at the given index.
+ void ErasePhiOperand(size_t index);
+
/// Orders the Phi arguments from farthest away to nearest.
void OrderPhiArgs();
diff --git a/src/shader_recompiler/ir_opt/dead_code_elimination_pass.cpp b/src/shader_recompiler/ir_opt/dead_code_elimination_pass.cpp
index 6c7c7b32d..6697fde85 100644
--- a/src/shader_recompiler/ir_opt/dead_code_elimination_pass.cpp
+++ b/src/shader_recompiler/ir_opt/dead_code_elimination_pass.cpp
@@ -2,6 +2,10 @@
// Licensed under GPLv2 or any later version
// Refer to the license.txt file included.
+#include <algorithm>
+
+#include <boost/container/small_vector.hpp>
+
#include "shader_recompiler/frontend/ir/basic_block.h"
#include "shader_recompiler/frontend/ir/value.h"
#include "shader_recompiler/ir_opt/passes.h"
@@ -25,7 +29,26 @@ void DeadInstElimination(IR::Block* const block) {
}
}
+void DeletedPhiArgElimination(IR::Program& program, std::span<const IR::Block*> dead_blocks) {
+ for (IR::Block* const block : program.blocks) {
+ for (IR::Inst& phi : *block) {
+ if (!IR::IsPhi(phi)) {
+ continue;
+ }
+ for (size_t i = 0; i < phi.NumArgs(); ++i) {
+ if (std::ranges::find(dead_blocks, phi.PhiBlock(i)) == dead_blocks.end()) {
+ continue;
+ }
+ // Phi operand at this index is an unreachable block
+ phi.ErasePhiOperand(i);
+ --i;
+ }
+ }
+ }
+}
+
void DeadBranchElimination(IR::Program& program) {
+ boost::container::small_vector<const IR::Block*, 3> dead_blocks;
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) {
@@ -55,6 +78,7 @@ void DeadBranchElimination(IR::Program& program) {
case IR::AbstractSyntaxNode::Type::Block: {
IR::Block* const block{node_it->data.block};
DeadInstElimination<false>(block);
+ dead_blocks.push_back(block);
break;
}
default:
@@ -66,6 +90,9 @@ void DeadBranchElimination(IR::Program& program) {
// Account for loop increment
--node_it;
}
+ if (!dead_blocks.empty()) {
+ DeletedPhiArgElimination(program, std::span(dead_blocks.data(), dead_blocks.size()));
+ }
}
} // namespace