From cbfb7d182a4e90e4e263696d1fca35e47d3eabb4 Mon Sep 17 00:00:00 2001
From: ReinUsesLisp <reinuseslisp@airmail.cc>
Date: Sun, 14 Feb 2021 20:15:42 -0300
Subject: shader: Support SSA loops on IR
---
src/shader_recompiler/ir_opt/ssa_rewrite_pass.cpp | 62 ++++++++++++++++++-----
1 file changed, 49 insertions(+), 13 deletions(-)
(limited to 'src/shader_recompiler/ir_opt/ssa_rewrite_pass.cpp')
diff --git a/src/shader_recompiler/ir_opt/ssa_rewrite_pass.cpp b/src/shader_recompiler/ir_opt/ssa_rewrite_pass.cpp
index 7eaf719c4e..13f9c914a2 100644
--- a/src/shader_recompiler/ir_opt/ssa_rewrite_pass.cpp
+++ b/src/shader_recompiler/ir_opt/ssa_rewrite_pass.cpp
@@ -14,7 +14,13 @@
// https://link.springer.com/chapter/10.1007/978-3-642-37051-9_6
//
+#include <ranges>
+#include <span>
+#include <variant>
+#include <vector>
+
#include <boost/container/flat_map.hpp>
+#include <boost/container/flat_set.hpp>
#include "shader_recompiler/frontend/ir/basic_block.h"
#include "shader_recompiler/frontend/ir/function.h"
@@ -26,9 +32,9 @@
namespace Shader::Optimization {
namespace {
-using ValueMap = boost::container::flat_map<IR::Block*, IR::Value, std::less<IR::Block*>>;
-
-struct FlagTag {};
+struct FlagTag {
+ auto operator<=>(const FlagTag&) const noexcept = default;
+};
struct ZeroFlagTag : FlagTag {};
struct SignFlagTag : FlagTag {};
struct CarryFlagTag : FlagTag {};
@@ -38,9 +44,15 @@ struct GotoVariable : FlagTag {
GotoVariable() = default;
explicit GotoVariable(u32 index_) : index{index_} {}
+ auto operator<=>(const GotoVariable&) const noexcept = default;
+
u32 index;
};
+using Variant = std::variant<IR::Reg, IR::Pred, ZeroFlagTag, SignFlagTag, CarryFlagTag,
+ OverflowFlagTag, GotoVariable>;
+using ValueMap = boost::container::flat_map<IR::Block*, IR::Value, std::less<IR::Block*>>;
+
struct DefTable {
[[nodiscard]] ValueMap& operator[](IR::Reg variable) noexcept {
return regs[IR::RegIndex(variable)];
@@ -102,19 +114,35 @@ public:
}
IR::Value ReadVariable(auto variable, IR::Block* block) {
- auto& def{current_def[variable]};
+ const ValueMap& def{current_def[variable]};
if (const auto it{def.find(block)}; it != def.end()) {
return it->second;
}
return ReadVariableRecursive(variable, block);
}
+ void SealBlock(IR::Block* block) {
+ const auto it{incomplete_phis.find(block)};
+ if (it != incomplete_phis.end()) {
+ for (auto& [variant, phi] : it->second) {
+ std::visit([&](auto& variable) { AddPhiOperands(variable, *phi, block); }, variant);
+ }
+ }
+ sealed_blocks.insert(block);
+ }
+
private:
IR::Value ReadVariableRecursive(auto variable, IR::Block* block) {
IR::Value val;
- if (const std::span preds{block->ImmediatePredecessors()}; preds.size() == 1) {
+ if (!sealed_blocks.contains(block)) {
+ // Incomplete CFG
+ IR::Inst* phi{&*block->PrependNewInst(block->begin(), IR::Opcode::Phi)};
+ incomplete_phis[block].insert_or_assign(variable, phi);
+ val = IR::Value{&*phi};
+ } else if (const std::span imm_preds{block->ImmediatePredecessors()};
+ imm_preds.size() == 1) {
// Optimize the common case of one predecessor: no phi needed
- val = ReadVariable(variable, preds.front());
+ val = ReadVariable(variable, imm_preds.front());
} else {
// Break potential cycles with operandless phi
IR::Inst& phi_inst{*block->PrependNewInst(block->begin(), IR::Opcode::Phi)};
@@ -127,8 +155,8 @@ private:
}
IR::Value AddPhiOperands(auto variable, IR::Inst& phi, IR::Block* block) {
- for (IR::Block* const pred : block->ImmediatePredecessors()) {
- phi.AddPhiOperand(pred, ReadVariable(variable, pred));
+ for (IR::Block* const imm_pred : block->ImmediatePredecessors()) {
+ phi.AddPhiOperand(imm_pred, ReadVariable(variable, imm_pred));
}
return TryRemoveTrivialPhi(phi, block, UndefOpcode(variable));
}
@@ -159,6 +187,9 @@ private:
return same;
}
+ boost::container::flat_set<IR::Block*> sealed_blocks;
+ boost::container::flat_map<IR::Block*, boost::container::flat_map<Variant, IR::Inst*>>
+ incomplete_phis;
DefTable current_def;
};
@@ -218,14 +249,19 @@ void VisitInst(Pass& pass, IR::Block* block, IR::Inst& inst) {
break;
}
}
+
+void VisitBlock(Pass& pass, IR::Block* block) {
+ for (IR::Inst& inst : block->Instructions()) {
+ VisitInst(pass, block, inst);
+ }
+ pass.SealBlock(block);
+}
} // Anonymous namespace
-void SsaRewritePass(IR::Function& function) {
+void SsaRewritePass(std::span<IR::Block* const> post_order_blocks) {
Pass pass;
- for (IR::Block* const block : function.blocks) {
- for (IR::Inst& inst : block->Instructions()) {
- VisitInst(pass, block, inst);
- }
+ for (IR::Block* const block : post_order_blocks | std::views::reverse) {
+ VisitBlock(pass, block);
}
}
--
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