From 7ccb8cc9eabfa3a39030312ba558cf7bc0856d4e Mon Sep 17 00:00:00 2001
From: Matt Arsenault <Matthew.Arsenault@amd.com>
Date: Fri, 28 Mar 2025 23:38:42 +0700
Subject: [PATCH] llvm-reduce: Add pass to reduce uselistorders

---
 llvm/tools/llvm-reduce/CMakeLists.txt         |  1 +
 llvm/tools/llvm-reduce/DeltaManager.cpp       |  1 +
 llvm/tools/llvm-reduce/DeltaPasses.def        |  1 +
 .../llvm-reduce/deltas/ReduceUseListOrder.cpp | 53 +++++++++++++++++++
 .../llvm-reduce/deltas/ReduceUseListOrder.h   | 23 ++++++++
 5 files changed, 79 insertions(+)
 create mode 100644 llvm/tools/llvm-reduce/deltas/ReduceUseListOrder.cpp
 create mode 100644 llvm/tools/llvm-reduce/deltas/ReduceUseListOrder.h

diff --git a/llvm/tools/llvm-reduce/CMakeLists.txt b/llvm/tools/llvm-reduce/CMakeLists.txt
index d1423e4c0895..1252f405acef 100644
--- a/llvm/tools/llvm-reduce/CMakeLists.txt
+++ b/llvm/tools/llvm-reduce/CMakeLists.txt
@@ -54,6 +54,7 @@ add_llvm_tool(llvm-reduce
   deltas/ReduceInstructionsMIR.cpp
   deltas/ReduceInstructionFlagsMIR.cpp
   deltas/ReduceIRReferences.cpp
+  deltas/ReduceUseListOrder.cpp
   deltas/ReduceVirtualRegisters.cpp
   deltas/ReduceRegisterMasks.cpp
   deltas/ReduceRegisterDefs.cpp
diff --git a/llvm/tools/llvm-reduce/DeltaManager.cpp b/llvm/tools/llvm-reduce/DeltaManager.cpp
index 74c1f1bfa5ea..8c4807e07830 100644
--- a/llvm/tools/llvm-reduce/DeltaManager.cpp
+++ b/llvm/tools/llvm-reduce/DeltaManager.cpp
@@ -46,6 +46,7 @@
 #include "deltas/ReduceRegisterUses.h"
 #include "deltas/ReduceSpecialGlobals.h"
 #include "deltas/ReduceTargetFeaturesAttr.h"
+#include "deltas/ReduceUseListOrder.h"
 #include "deltas/ReduceUsingSimplifyCFG.h"
 #include "deltas/ReduceVirtualRegisters.h"
 #include "deltas/RunIRPasses.h"
diff --git a/llvm/tools/llvm-reduce/DeltaPasses.def b/llvm/tools/llvm-reduce/DeltaPasses.def
index 84d01ab6646b..6993a384fc8e 100644
--- a/llvm/tools/llvm-reduce/DeltaPasses.def
+++ b/llvm/tools/llvm-reduce/DeltaPasses.def
@@ -53,6 +53,7 @@ DELTA_PASS_IR("volatile", reduceVolatileInstructionsDeltaPass, "Reducing Volatil
 DELTA_PASS_IR("atomic-ordering", reduceAtomicOrderingDeltaPass, "Reducing Atomic Ordering")
 DELTA_PASS_IR("syncscopes", reduceAtomicSyncScopesDeltaPass, "Reducing Atomic Sync Scopes")
 DELTA_PASS_IR("instruction-flags", reduceInstructionFlagsDeltaPass, "Reducing Instruction Flags")
+DELTA_PASS_IR("uselistorder", reduceUseListOrderDeltaPass, "Reducing uselistorder")
 
 
 #ifndef DELTA_PASS_MIR
diff --git a/llvm/tools/llvm-reduce/deltas/ReduceUseListOrder.cpp b/llvm/tools/llvm-reduce/deltas/ReduceUseListOrder.cpp
new file mode 100644
index 000000000000..97d88d5c7986
--- /dev/null
+++ b/llvm/tools/llvm-reduce/deltas/ReduceUseListOrder.cpp
@@ -0,0 +1,53 @@
+//===- ReduceUseListOrder.cpp - Specialized Delta Pass --------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements a function which calls the Generic Delta pass to reduce
+// global value attributes/specifiers.
+//
+//===----------------------------------------------------------------------===//
+
+#include "ReduceUseListOrder.h"
+
+using namespace llvm;
+
+static void reduceUseListOrder(Oracle &O, Value &V) {
+  if (!V.hasNUsesOrMore(2))
+    return;
+
+  // TODO: Extract predictUseListOrder out of AsmWriter
+
+  // TODO: Skip if use list already sorted
+  if (O.shouldKeep())
+    return;
+  ArrayRef<unsigned> Indexes;
+  unsigned NumUses = 0;
+  SmallDenseMap<const Use *, unsigned, 16> Order;
+  for (const Use &U : V.uses())
+    Order[&U] = Indexes[NumUses - 1];
+
+  V.sortUseList([&](const Use &L, const Use &R) {
+    return Order.lookup(&L) < Order.lookup(&R);
+  });
+}
+
+void llvm::reduceUseListOrderDeltaPass(Oracle &O, ReducerWorkItem &Program) {
+  Module &M = Program.getModule();
+
+  for (Function &F : M) {
+    reduceUseListOrder(O, F);
+
+    for (BasicBlock &BB : F) {
+      reduceUseListOrder(O, BB);
+      for (Instruction &I : BB)
+        reduceUseListOrder(O, I);
+    }
+  }
+
+  for (GlobalValue &GV : M.global_values())
+    reduceUseListOrder(O, GV);
+}
diff --git a/llvm/tools/llvm-reduce/deltas/ReduceUseListOrder.h b/llvm/tools/llvm-reduce/deltas/ReduceUseListOrder.h
new file mode 100644
index 000000000000..5638fe0a8380
--- /dev/null
+++ b/llvm/tools/llvm-reduce/deltas/ReduceUseListOrder.h
@@ -0,0 +1,23 @@
+//===- ReduceUseListOrder.h - Specialized Delta Pass ------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements a function which calls the Generic Delta pass to sort
+// uselistorder
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_TOOLS_LLVM_REDUCE_DELTAS_REDUCEUSELISTORDER_H
+#define LLVM_TOOLS_LLVM_REDUCE_DELTAS_REDUCEUSELISTORDER_H
+
+#include "Delta.h"
+
+namespace llvm {
+void reduceUseListOrderDeltaPass(Oracle &O, ReducerWorkItem &Program);
+} // namespace llvm
+
+#endif
-- 
2.49.0