read-write function argument promotion pass

llvm/include/llvm/Transforms/IPO/MSSAArgPromotion.h

@@ -0,0 +1,26 @@
+//===- MSSAArgPromotionPass.cpp - Promote by-reference arguments -----===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+//
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Analysis/CGSCCPassManager.h"
+#include "llvm/Analysis/LazyCallGraph.h"
+#include "llvm/IR/PassManager.h"
+
+namespace llvm {
+
+class MSSAArgPromotionPass : public PassInfoMixin<MSSAArgPromotionPass> {
+public:
+  MSSAArgPromotionPass() {}
+
+  PreservedAnalyses run(LazyCallGraph::SCC &C, CGSCCAnalysisManager &AM,
+                        LazyCallGraph &CG, CGSCCUpdateResult &UR);
+};
+
+} // end namespace llvm

llvm/lib/Passes/PassBuilder.cpp

@@ -229,6 +229,7 @@
 #include "llvm/Transforms/IPO/LoopExtractor.h"
 #include "llvm/Transforms/IPO/LowerTypeTests.h"
 #include "llvm/Transforms/IPO/MemProfContextDisambiguation.h"
+#include "llvm/Transforms/IPO/MSSAArgPromotion.h"
 #include "llvm/Transforms/IPO/MergeFunctions.h"
 #include "llvm/Transforms/IPO/OpenMPOpt.h"
 #include "llvm/Transforms/IPO/PartialInlining.h"

llvm/lib/Passes/PassRegistry.def

@@ -322,6 +322,7 @@ CGSCC_ANALYSIS("pass-instrumentation", PassInstrumentationAnalysis(PIC))
 CGSCC_PASS("argpromotion", ArgumentPromotionPass())
 CGSCC_PASS("attributor-cgscc", AttributorCGSCCPass())
 CGSCC_PASS("attributor-light-cgscc", AttributorLightCGSCCPass())
+CGSCC_PASS("mssaargpromotion", MSSAArgPromotionPass())
 CGSCC_PASS("invalidate<all>", InvalidateAllAnalysesPass())
 CGSCC_PASS("no-op-cgscc", NoOpCGSCCPass())
 CGSCC_PASS("openmp-opt-cgscc", OpenMPOptCGSCCPass())

llvm/lib/Target/AMDGPU/AMDGPUTargetMachine.cpp

@@ -102,6 +102,7 @@
 #include "llvm/Transforms/IPO/ExpandVariadics.h"
 #include "llvm/Transforms/IPO/GlobalDCE.h"
 #include "llvm/Transforms/IPO/Internalize.h"
+#include "llvm/Transforms/IPO/MSSAArgPromotion.h"
 #include "llvm/Transforms/Scalar.h"
 #include "llvm/Transforms/Scalar/EarlyCSE.h"
 #include "llvm/Transforms/Scalar/FlattenCFG.h"
@@ -949,6 +950,10 @@ void AMDGPUTargetMachine::registerPassBuilderCallbacks(PassBuilder &PB) {
           FPM.addPass(AMDGPUPromoteAllocaToVectorPass(*this));
         }
 
+        // Add pass to promote arguments passed by reference
+        if (Level.getSpeedupLevel() >= OptimizationLevel::O3.getSpeedupLevel())
+          PM.addPass(MSSAArgPromotionPass());
+
         PM.addPass(createCGSCCToFunctionPassAdaptor(std::move(FPM)));
       });
 

llvm/lib/Transforms/IPO/CMakeLists.txt

@@ -33,6 +33,7 @@ add_llvm_component_library(LLVMipo
   MemProfContextDisambiguation.cpp
   MergeFunctions.cpp
   ModuleInliner.cpp
+  MSSAArgPromotion.cpp
   OpenMPOpt.cpp
   PartialInlining.cpp
   SampleContextTracker.cpp