From 6be564960c1721d7951b1eca0e133dab6140e054 Mon Sep 17 00:00:00 2001
From: Mark Peerdeman <mark.peerdeman@leaningtech.com>
Date: Tue, 12 Dec 2023 15:14:15 +0100
Subject: [PATCH] Introduce temporary CheerpLowerAtomic pass

This pass is meant to remove atomics by invoking the existing LowerAtomicPass only on genericjs functions.
---
 clang/lib/CodeGen/BackendUtil.cpp            |  6 ++---
 llvm/include/llvm/Cheerp/CheerpLowerAtomic.h | 18 ++++++++++++++
 llvm/lib/CheerpUtils/CMakeLists.txt          |  1 +
 llvm/lib/CheerpUtils/CheerpLowerAtomic.cpp   | 26 ++++++++++++++++++++
 4 files changed, 48 insertions(+), 3 deletions(-)
 create mode 100644 llvm/include/llvm/Cheerp/CheerpLowerAtomic.h
 create mode 100644 llvm/lib/CheerpUtils/CheerpLowerAtomic.cpp

diff --git a/clang/lib/CodeGen/BackendUtil.cpp b/clang/lib/CodeGen/BackendUtil.cpp
index b6d114ffc677..b4b2ab17898c 100644
--- a/clang/lib/CodeGen/BackendUtil.cpp
+++ b/clang/lib/CodeGen/BackendUtil.cpp
@@ -28,6 +28,7 @@
 #include "llvm/Bitcode/BitcodeWriterPass.h"
 #include "llvm/Cheerp/NativeRewriter.h"
 #include "llvm/Cheerp/CFGPasses.h"
+#include "llvm/Cheerp/CheerpLowerAtomic.h"
 #include "llvm/Cheerp/ByValLowering.h"
 #include "llvm/Cheerp/PassUtility.h"
 #include "llvm/CodeGen/RegAllocRegistry.h"
@@ -87,7 +88,6 @@
 #include "llvm/Transforms/Scalar/EarlyCSE.h"
 #include "llvm/Transforms/Scalar/GVN.h"
 #include "llvm/Transforms/Scalar/JumpThreading.h"
-#include "llvm/Transforms/Scalar/LowerAtomicPass.h"
 #include "llvm/Transforms/Scalar/LowerMatrixIntrinsics.h"
 #include "llvm/Transforms/Utils.h"
 #include "llvm/Transforms/Utils/CanonicalizeAliases.h"
@@ -947,8 +947,8 @@ void EmitAssemblyHelper::RunOptimizationPipeline(
             //We need this to track this in custom constructors for DOM types, such as String::String(const char*)
             MPM.addPass(createModuleToFunctionPassAdaptor(cheerp::RequiredPassWrapper<PromotePass>()));
             MPM.addPass(createModuleToFunctionPassAdaptor(cheerp::CheerpNativeRewriterPass()));
-            //Cheerp is single threaded, convert atomic instructions to regular ones
-            MPM.addPass(createModuleToFunctionPassAdaptor(LowerAtomicPass()));
+            // This temporary pass will remove atomics from genericjs functions
+            MPM.addPass(cheerp::CheerpLowerAtomicPass());
           });
       PB.registerOptimizerLastEPCallback(
           [](ModulePassManager &MPM, OptimizationLevel Level) {
diff --git a/llvm/include/llvm/Cheerp/CheerpLowerAtomic.h b/llvm/include/llvm/Cheerp/CheerpLowerAtomic.h
new file mode 100644
index 000000000000..a4b1c98a5ad6
--- /dev/null
+++ b/llvm/include/llvm/Cheerp/CheerpLowerAtomic.h
@@ -0,0 +1,18 @@
+#ifndef CHEERP_LOWER_ATOMIC_H
+#define CHEERP_LOWER_ATOMIC_H
+
+#include "llvm/IR/PassManager.h"
+
+namespace cheerp
+{
+
+class CheerpLowerAtomicPass : public llvm::PassInfoMixin<CheerpLowerAtomicPass>
+{
+public:
+	llvm::PreservedAnalyses run(llvm::Module& M, llvm::ModuleAnalysisManager& MAM);
+	static bool isRequired() { return true; }
+};
+
+}
+
+#endif
diff --git a/llvm/lib/CheerpUtils/CMakeLists.txt b/llvm/lib/CheerpUtils/CMakeLists.txt
index c7987f9b4da4..74ceb1015ed8 100644
--- a/llvm/lib/CheerpUtils/CMakeLists.txt
+++ b/llvm/lib/CheerpUtils/CMakeLists.txt
@@ -33,6 +33,7 @@ add_llvm_component_library(LLVMCheerpUtils
   BitCastLowering.cpp
   JSStringLiteralLowering.cpp
   MemoryInit.cpp
+  CheerpLowerAtomic.cpp
   )
 
 add_dependencies(LLVMCheerpUtils intrinsics_gen)
diff --git a/llvm/lib/CheerpUtils/CheerpLowerAtomic.cpp b/llvm/lib/CheerpUtils/CheerpLowerAtomic.cpp
new file mode 100644
index 000000000000..e7d4c5aa330b
--- /dev/null
+++ b/llvm/lib/CheerpUtils/CheerpLowerAtomic.cpp
@@ -0,0 +1,26 @@
+#include "llvm/Cheerp/CheerpLowerAtomic.h"
+#include "llvm/Transforms/Scalar/LowerAtomicPass.h"
+
+using namespace llvm;
+using namespace cheerp;
+// Module pass that invokes the LLVM LowerAtomicPass on genericjs functions.
+PreservedAnalyses CheerpLowerAtomicPass::run(Module& M, ModuleAnalysisManager& MAM)
+{
+	FunctionAnalysisManager& FAM = MAM.getResult<FunctionAnalysisManagerModuleProxy>(M).getManager();
+	FunctionPassManager FPM;
+	FPM.addPass(LowerAtomicPass());
+
+	// Loop over the functions, and only pass genericjs ones to LowerAtomicPass
+	for (Function& F : M)
+	{
+		if (F.isDeclaration())
+			continue;
+
+		if (F.getSection() == "asmjs")
+			continue;
+
+		FPM.run(F, FAM);
+	}
+
+	return PreservedAnalyses::none();
+}