From 76fa2becebef585658bf1a910ea50d78056ce33f Mon Sep 17 00:00:00 2001
From: Celegans12 <53881228+Celegans12@users.noreply.github.com>
Date: Sun, 11 Oct 2026 16:06:57 +0200
Subject: [PATCH] perf(recompiler): reuse sorted sets for iteration selection
 merges

Seed each iteration-selection update from its first eligible successor
instead of rebuilding and intersecting the universe of block IDs.
Reuse the existing in-place intersection and sorted-insertion helpers
while preserving the original empty-successor and fixed-point behavior.
Keep a cache-neutral switch for same-binary output and timing comparisons.
Run the existing structurizer and control-flow fixtures in a separate
process with this optimization disabled as well as in their default mode.
---
 core/libs/prx/libSceAgcDriver/CMakeLists.txt  |  6 ++++-
 .../ControlFlow/src/Structurizer.cpp          | 25 +++++++++++++++----
 core/shader/recompiler/ShaderDiskCache.cpp    |  1 +
 3 files changed, 26 insertions(+), 6 deletions(-)

diff --git a/core/libs/prx/libSceAgcDriver/CMakeLists.txt b/core/libs/prx/libSceAgcDriver/CMakeLists.txt
index bef499a10..6956e6e5a 100644
--- a/core/libs/prx/libSceAgcDriver/CMakeLists.txt
+++ b/core/libs/prx/libSceAgcDriver/CMakeLists.txt
@@ -1021,8 +1021,12 @@ if(BUILD_TESTING)
     endif()
     add_test(NAME agc_structurizer_intersection_off COMMAND agc_structurizer_tests)
     set_tests_properties(agc_structurizer_intersection_off PROPERTIES ENVIRONMENT "ANYPS5_NO_SHADER_CACHE=1;APS5_NO_PERF_DOM_INTERSECTION=1" WORKING_DIRECTORY "${CMAKE_SOURCE_DIR}")
+    add_test(NAME agc_structurizer_iteration_selection_off COMMAND agc_structurizer_tests)
+    set_tests_properties(agc_structurizer_iteration_selection_off PROPERTIES ENVIRONMENT "ANYPS5_NO_SHADER_CACHE=1;APS5_NO_PERF_ITERATION_SELECTION=1" WORKING_DIRECTORY "${CMAKE_SOURCE_DIR}")
+    add_test(NAME agc_shader_control_flow_iteration_selection_off COMMAND agc_shader_control_flow_tests)
+    set_tests_properties(agc_shader_control_flow_iteration_selection_off PROPERTIES ENVIRONMENT "ANYPS5_NO_SHADER_CACHE=1;APS5_NO_PERF_ITERATION_SELECTION=1" WORKING_DIRECTORY "${CMAKE_SOURCE_DIR}")
     if(WIN32)
-        set_tests_properties(agc_structurizer_intersection_off PROPERTIES ENVIRONMENT_MODIFICATION "PATH=path_list_prepend:$<TARGET_FILE_DIR:libc>")
+        set_tests_properties(agc_structurizer_intersection_off agc_structurizer_iteration_selection_off agc_shader_control_flow_iteration_selection_off PROPERTIES ENVIRONMENT_MODIFICATION "PATH=path_list_prepend:$<TARGET_FILE_DIR:libc>")
     endif()
     add_test(NAME agc_driver_gated_dispatch_capture_short_timeout COMMAND agc_driver_gated_dispatch_capture_tests)
     set_tests_properties(agc_driver_gated_dispatch_capture_short_timeout PROPERTIES
diff --git a/core/shader/recompiler/ControlFlow/src/Structurizer.cpp b/core/shader/recompiler/ControlFlow/src/Structurizer.cpp
index e4cb6e53b..70193cd42 100644
--- a/core/shader/recompiler/ControlFlow/src/Structurizer.cpp
+++ b/core/shader/recompiler/ControlFlow/src/Structurizer.cpp
@@ -428,6 +428,7 @@ std::uint32_t mergeBesideReturns(const ControlFlowGraph& graph, const BasicBlock
 
 std::uint32_t iterationSelectionMerge(const ControlFlowGraph& graph, const NaturalLoop& loop, const BasicBlock& header, std::uint32_t join) {
     const auto count = static_cast<std::uint32_t>(graph.blocks.size());
+    static const bool reuse = std::getenv("APS5_NO_PERF_ITERATION_SELECTION") == nullptr;
     const auto escapes = [&](std::uint32_t blockId) { return blockId == loop.continueBlock || blockId == loop.mergeBlock; };
     std::vector<bool> joins(count, false);
     std::vector<std::uint32_t> pending = {join};
@@ -455,16 +456,30 @@ std::uint32_t iterationSelectionMerge(const ControlFlowGraph& graph, const Natur
             if (!joins[block.id] || block.id == join) {
                 continue;
             }
-            auto next = allBlockIds(count);
+            bool seeded = !reuse;
+            auto next = seeded ? allBlockIds(count) : std::vector<std::uint32_t>{};
             for (const auto successor : block.successors) {
                 if (joins[successor]) {
-                    next = intersectSorted(next, postDominators[successor]);
+                    if (!seeded) {
+                        next = postDominators[successor];
+                        seeded = true;
+                    } else if (reuse) {
+                        intersectAnalysisSet(next, postDominators[successor]);
+                    } else {
+                        next = intersectSorted(next, postDominators[successor]);
+                    }
                 }
             }
-            addUnique(next, block.id);
-            sortUnique(next);
+            if (!seeded) next = allBlockIds(count);
+            if (reuse) {
+                addSortedUnique(next, block.id);
+            } else {
+                addUnique(next, block.id);
+                sortUnique(next);
+            }
             if (next != postDominators[block.id]) {
-                postDominators[block.id] = std::move(next);
+                if (reuse) replaceAnalysisSet(postDominators[block.id], std::move(next));
+                else postDominators[block.id] = std::move(next);
                 changed = true;
             }
         }
diff --git a/core/shader/recompiler/ShaderDiskCache.cpp b/core/shader/recompiler/ShaderDiskCache.cpp
index bd05440bc..203770688 100644
--- a/core/shader/recompiler/ShaderDiskCache.cpp
+++ b/core/shader/recompiler/ShaderDiskCache.cpp
@@ -671,6 +671,7 @@ constexpr std::string_view NeutralSwitches[] = {
     "APS5_NO_FAILURE_MEMO",
     "APS5_NO_PERF_FRONTEND_PAIR",
     "APS5_NO_PERF_DOM_INTERSECTION",
+    "APS5_NO_PERF_ITERATION_SELECTION",
     "APS5_NO_RESULT_MEMO",
 };