Run ObjCContractPass in Default Codegen Pipeline (#92331)

Prior to this patch, when using -fthinlto-index= the ObjCARCContractPass isn't run prior to CodeGen, and instruction selection fails on IR containing arc intrinsics. This patch is motivated by that usecase.

The pass was previously added in various places codegen is performed. This patch adds the pass to the default codegen pipepline, makes sure it bails immediately if no arc intrinsics are found, and removes the adhoc scheduling of the pass. 

Co-authored-by: Nuri Amari <[email protected]>

Author: NuriAmari

clang/lib/CodeGen/BackendUtil.cpp

@@ -587,12 +587,6 @@ bool EmitAssemblyHelper::AddEmitPasses(legacy::PassManager &CodeGenPasses,
   // this also adds codegenerator level optimization passes.
   CodeGenFileType CGFT = getCodeGenFileType(Action);
 
-  // Add ObjC ARC final-cleanup optimizations. This is done as part of the
-  // "codegen" passes so that it isn't run multiple times when there is
-  // inlining happening.
-  if (CodeGenOpts.OptimizationLevel > 0)
-    CodeGenPasses.add(createObjCARCContractPass());
-
   if (TM->addPassesToEmitFile(CodeGenPasses, OS, DwoOS, CGFT,
                               /*DisableVerify=*/!CodeGenOpts.VerifyModule)) {
     Diags.Report(diag::err_fe_unable_to_interface_with_target);

clang/test/CodeGen/thinlto-distributed-objc-contract-pass.ll

@@ -0,0 +1,19 @@
+; RUN: opt -thinlto-bc -o %t.o %s
+
+; RUN: llvm-lto2 run -thinlto-distributed-indexes %t.o \
+; RUN:   -o %t2.index \
+; RUN:   -r=%t.o,_use_arc,px
+
+; RUN: %clang_cc1 -triple x86_64-apple-darwin \
+; RUN:   -emit-obj -fthinlto-index=%t.o.thinlto.bc \
+; RUN:   -o %t.native.o -x ir %t.o
+
+target datalayout = "e-m:o-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-apple-darwin"
+
+define void @use_arc(ptr %a, ptr %b) {
+  call void (...) @llvm.objc.clang.arc.use(ptr %a, ptr %b) nounwind
+  ret void
+}
+
+declare void @llvm.objc.clang.arc.use(...) nounwind

lld/MachO/LTO.cpp

@@ -48,9 +48,6 @@ static lto::Config createConfig() {
   c.CPU = getCPUStr();
   c.MAttrs = getMAttrs();
   c.DiagHandler = diagnosticHandler;
-  c.PreCodeGenPassesHook = [](legacy::PassManager &pm) {
-    pm.add(createObjCARCContractPass());
-  };
 
   c.AlwaysEmitRegularLTOObj = !config->ltoObjPath.empty();
 

llvm/include/llvm/Analysis/ObjCARCAnalysisUtils.h

@@ -41,26 +41,26 @@ extern bool EnableARCOpts;
 /// Test if the given module looks interesting to run ARC optimization
 /// on.
 inline bool ModuleHasARC(const Module &M) {
-  return
-    M.getNamedValue("llvm.objc.retain") ||
-    M.getNamedValue("llvm.objc.release") ||
-    M.getNamedValue("llvm.objc.autorelease") ||
-    M.getNamedValue("llvm.objc.retainAutoreleasedReturnValue") ||
-    M.getNamedValue("llvm.objc.unsafeClaimAutoreleasedReturnValue") ||
-    M.getNamedValue("llvm.objc.retainBlock") ||
-    M.getNamedValue("llvm.objc.autoreleaseReturnValue") ||
-    M.getNamedValue("llvm.objc.autoreleasePoolPush") ||
-    M.getNamedValue("llvm.objc.loadWeakRetained") ||
-    M.getNamedValue("llvm.objc.loadWeak") ||
-    M.getNamedValue("llvm.objc.destroyWeak") ||
-    M.getNamedValue("llvm.objc.storeWeak") ||
-    M.getNamedValue("llvm.objc.initWeak") ||
-    M.getNamedValue("llvm.objc.moveWeak") ||
-    M.getNamedValue("llvm.objc.copyWeak") ||
-    M.getNamedValue("llvm.objc.retainedObject") ||
-    M.getNamedValue("llvm.objc.unretainedObject") ||
-    M.getNamedValue("llvm.objc.unretainedPointer") ||
-    M.getNamedValue("llvm.objc.clang.arc.use");
+  return M.getNamedValue("llvm.objc.retain") ||
+         M.getNamedValue("llvm.objc.release") ||
+         M.getNamedValue("llvm.objc.autorelease") ||
+         M.getNamedValue("llvm.objc.retainAutoreleasedReturnValue") ||
+         M.getNamedValue("llvm.objc.unsafeClaimAutoreleasedReturnValue") ||
+         M.getNamedValue("llvm.objc.retainBlock") ||
+         M.getNamedValue("llvm.objc.autoreleaseReturnValue") ||
+         M.getNamedValue("llvm.objc.autoreleasePoolPush") ||
+         M.getNamedValue("llvm.objc.loadWeakRetained") ||
+         M.getNamedValue("llvm.objc.loadWeak") ||
+         M.getNamedValue("llvm.objc.destroyWeak") ||
+         M.getNamedValue("llvm.objc.storeWeak") ||
+         M.getNamedValue("llvm.objc.initWeak") ||
+         M.getNamedValue("llvm.objc.moveWeak") ||
+         M.getNamedValue("llvm.objc.copyWeak") ||
+         M.getNamedValue("llvm.objc.retainedObject") ||
+         M.getNamedValue("llvm.objc.unretainedObject") ||
+         M.getNamedValue("llvm.objc.unretainedPointer") ||
+         M.getNamedValue("llvm.objc.clang.arc.noop.use") ||
+         M.getNamedValue("llvm.objc.clang.arc.use");
 }
 
 /// This is a wrapper around getUnderlyingObject which also knows how to

llvm/lib/CodeGen/TargetPassConfig.cpp

@@ -46,6 +46,7 @@
 #include "llvm/Support/WithColor.h"
 #include "llvm/Target/CGPassBuilderOption.h"
 #include "llvm/Target/TargetMachine.h"
+#include "llvm/Transforms/ObjCARC.h"
 #include "llvm/Transforms/Scalar.h"
 #include "llvm/Transforms/Utils.h"
 #include <cassert>
@@ -946,6 +947,8 @@ void TargetPassConfig::addCodeGenPrepare() {
 void TargetPassConfig::addISelPrepare() {
   addPreISel();
 
+  addPass(createObjCARCContractPass());
+
   // Force codegen to run according to the callgraph.
   if (requiresCodeGenSCCOrder())
     addPass(new DummyCGSCCPass);

llvm/lib/LTO/LTOCodeGenerator.cpp

@@ -137,10 +137,6 @@ LTOCodeGenerator::LTOCodeGenerator(LLVMContext &Context)
 
   Config.CodeModel = std::nullopt;
   Config.StatsFile = LTOStatsFile;
-  Config.PreCodeGenPassesHook = [](legacy::PassManager &PM) {
-    PM.add(createObjCARCContractPass());
-  };
-
   Config.RunCSIRInstr = LTORunCSIRInstr;
   Config.CSIRProfile = LTOCSIRProfile;
 }

llvm/lib/LTO/ThinLTOCodeGenerator.cpp

@@ -334,10 +334,6 @@ std::unique_ptr<MemoryBuffer> codegenModule(Module &TheModule,
     raw_svector_ostream OS(OutputBuffer);
     legacy::PassManager PM;
 
-    // If the bitcode files contain ARC code and were compiled with optimization,
-    // the ObjCARCContractPass must be run, so do it unconditionally here.
-    PM.add(createObjCARCContractPass());
-
     // Setup the codegen now.
     if (TM.addPassesToEmitFile(PM, OS, nullptr, CodeGenFileType::ObjectFile,
                                /* DisableVerify */ true))

llvm/lib/Transforms/ObjCARC/ObjCARCContract.cpp

@@ -71,6 +71,9 @@ class ObjCARCContract {
   ARCRuntimeEntryPoints EP;
   BundledRetainClaimRVs *BundledInsts = nullptr;
 
+  /// A flag indicating whether this optimization pass should run.
+  bool Run;
+
   /// The inline asm string to insert between calls and RetainRV calls to make
   /// the optimization work on targets which need it.
   const MDString *RVInstMarker;
@@ -527,6 +530,10 @@ bool ObjCARCContract::tryToPeepholeInstruction(
 //===----------------------------------------------------------------------===//
 
 bool ObjCARCContract::init(Module &M) {
+  Run = ModuleHasARC(M);
+  if (!Run)
+    return false;
+
   EP.init(&M);
 
   // Initialize RVInstMarker.
@@ -539,6 +546,9 @@ bool ObjCARCContract::run(Function &F, AAResults *A, DominatorTree *D) {
   if (!EnableARCOpts)
     return false;
 
+  if (!Run)
+    return false;
+
   Changed = CFGChanged = false;
   AA = A;
   DT = D;

llvm/test/CodeGen/AArch64/O0-pipeline.ll

@@ -31,6 +31,10 @@
 ; CHECK-NEXT:       AArch64 Stack Tagging
 ; CHECK-NEXT:       SME ABI Pass
 ; CHECK-NEXT:       Exception handling preparation
+; CHECK-NEXT:       Dominator Tree Construction
+; CHECK-NEXT:       Basic Alias Analysis (stateless AA impl)
+; CHECK-NEXT:       Function Alias Analysis Results
+; CHECK-NEXT:       ObjC ARC contraction
 ; CHECK-NEXT:       Prepare callbr
 ; CHECK-NEXT:       Safe Stack instrumentation pass
 ; CHECK-NEXT:       Insert stack protectors

llvm/test/CodeGen/AArch64/O3-pipeline.ll

@@ -103,6 +103,10 @@
 ; CHECK-NEXT:         Dominator Tree Construction
 ; CHECK-NEXT:     FunctionPass Manager
 ; CHECK-NEXT:       Merge internal globals
+; CHECK-NEXT:       Dominator Tree Construction
+; CHECK-NEXT:       Basic Alias Analysis (stateless AA impl)
+; CHECK-NEXT:       Function Alias Analysis Results
+; CHECK-NEXT:       ObjC ARC contraction
 ; CHECK-NEXT:       Prepare callbr
 ; CHECK-NEXT:       Safe Stack instrumentation pass
 ; CHECK-NEXT:       Insert stack protectors