Remove -lower-global-dtors-via-cxa-atexit flag

Remove the `-lower-global-dtors-via-cxa-atexit` escape hatch introduced
in D121736 [1], which switched the default lowering of global
destructors on MachO to use `__cxa_atexit()` to avoid emitting
deprecated `__mod_term_func` sections.

I added this flag as an escape hatch in case the switch causes any
problems.  We didn't discover any problems so now we can remove it.

[1] https://reviews.llvm.org/D121736

rdar://90277838

Differential Revision: https://reviews.llvm.org/D145715

diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 4a5d3f8..06e4cd2 100644 (file)
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -132,6 +132,9 @@ Removed Compiler Flags
   or higher to use standard C++ modules instead.
 - The deprecated flag `-fcoroutines-ts` is removed. Please use ``-std=c++20``
   or higher to use standard C++ coroutines instead.
+- The CodeGen flag `-lower-global-dtors-via-cxa-atexit` which affects how global
+  destructors are lowered for MachO is removed without replacement. The default
+  of `-lower-global-dtors-via-cxa-atexit=true` is now the only supported way.
 
 Attribute Changes in Clang
 --------------------------

diff --git a/clang/lib/CodeGen/BackendUtil.cpp b/clang/lib/CodeGen/BackendUtil.cpp
index b03d326..fffaeb8 100644 (file)
--- a/clang/lib/CodeGen/BackendUtil.cpp
+++ b/clang/lib/CodeGen/BackendUtil.cpp
@@ -367,8 +367,6 @@ static bool initTargetOptions(DiagnosticsEngine &Diags,
   Options.BinutilsVersion =
       llvm::TargetMachine::parseBinutilsVersion(CodeGenOpts.BinutilsVersion);
   Options.UseInitArray = CodeGenOpts.UseInitArray;
-  Options.LowerGlobalDtorsViaCxaAtExit =
-      CodeGenOpts.RegisterGlobalDtorsWithAtExit;
   Options.DisableIntegratedAS = CodeGenOpts.DisableIntegratedAS;
   Options.CompressDebugSections = CodeGenOpts.getCompressDebugSections();
   Options.RelaxELFRelocations = CodeGenOpts.RelaxELFRelocations;

diff --git a/llvm/include/llvm/CodeGen/CommandFlags.h b/llvm/include/llvm/CodeGen/CommandFlags.h
index 7b1ef60..475d87b 100644 (file)
--- a/llvm/include/llvm/CodeGen/CommandFlags.h
+++ b/llvm/include/llvm/CodeGen/CommandFlags.h
@@ -94,8 +94,6 @@ std::string getTrapFuncName();
 
 bool getUseCtors();
 
-bool getLowerGlobalDtorsViaCxaAtExit();
-
 bool getRelaxELFRelocations();
 
 bool getDataSections();

diff --git a/llvm/include/llvm/Target/TargetOptions.h b/llvm/include/llvm/Target/TargetOptions.h
index d8a4159..22e8116 100644 (file)
--- a/llvm/include/llvm/Target/TargetOptions.h
+++ b/llvm/include/llvm/Target/TargetOptions.h
@@ -130,7 +130,7 @@ namespace llvm {
           HonorSignDependentRoundingFPMathOption(false), NoZerosInBSS(false),
           GuaranteedTailCallOpt(false), StackSymbolOrdering(true),
           EnableFastISel(false), EnableGlobalISel(false), UseInitArray(false),
-          LowerGlobalDtorsViaCxaAtExit(false), DisableIntegratedAS(false),
+          DisableIntegratedAS(false),
           RelaxELFRelocations(true), FunctionSections(false),
           DataSections(false), IgnoreXCOFFVisibility(false),
           XCOFFTracebackTable(true), UniqueSectionNames(true),
@@ -247,10 +247,6 @@ namespace llvm {
     /// constructors.
     unsigned UseInitArray : 1;
 
-    /// Use __cxa_atexit to register global destructors; determines how
-    /// llvm.global_dtors is lowered.
-    unsigned LowerGlobalDtorsViaCxaAtExit : 1;
-
     /// Disable the integrated assembler.
     unsigned DisableIntegratedAS : 1;
 

diff --git a/llvm/lib/CodeGen/CommandFlags.cpp b/llvm/lib/CodeGen/CommandFlags.cpp
index 73521ac..51d259c 100644 (file)
--- a/llvm/lib/CodeGen/CommandFlags.cpp
+++ b/llvm/lib/CodeGen/CommandFlags.cpp
@@ -81,7 +81,6 @@ CGOPT(bool, StackSymbolOrdering)
 CGOPT(bool, StackRealign)
 CGOPT(std::string, TrapFuncName)
 CGOPT(bool, UseCtors)
-CGOPT(bool, LowerGlobalDtorsViaCxaAtExit)
 CGOPT(bool, RelaxELFRelocations)
 CGOPT_EXP(bool, DataSections)
 CGOPT_EXP(bool, FunctionSections)
@@ -349,12 +348,6 @@ codegen::RegisterCodeGenFlags::RegisterCodeGenFlags() {
                                 cl::init(false));
   CGBINDOPT(UseCtors);
 
-  static cl::opt<bool> LowerGlobalDtorsViaCxaAtExit(
-      "lower-global-dtors-via-cxa-atexit",
-      cl::desc("Lower llvm.global_dtors (global destructors) via __cxa_atexit"),
-      cl::init(true));
-  CGBINDOPT(LowerGlobalDtorsViaCxaAtExit);
-
   static cl::opt<bool> RelaxELFRelocations(
       "relax-elf-relocations",
       cl::desc(
@@ -538,7 +531,6 @@ codegen::InitTargetOptionsFromCodeGenFlags(const Triple &TheTriple) {
   Options.GuaranteedTailCallOpt = getEnableGuaranteedTailCallOpt();
   Options.StackSymbolOrdering = getStackSymbolOrdering();
   Options.UseInitArray = !getUseCtors();
-  Options.LowerGlobalDtorsViaCxaAtExit = getLowerGlobalDtorsViaCxaAtExit();
   Options.RelaxELFRelocations = getRelaxELFRelocations();
   Options.DataSections =
       getExplicitDataSections().value_or(TheTriple.hasDefaultDataSections());

diff --git a/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp b/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
index 5f9e9ea..e2fbe02 100644 (file)
--- a/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
+++ b/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
@@ -1202,11 +1202,7 @@ void TargetLoweringObjectFileMachO::Initialize(MCContext &Ctx,
 
 MCSection *TargetLoweringObjectFileMachO::getStaticDtorSection(
     unsigned Priority, const MCSymbol *KeySym) const {
-  // TODO(yln): Remove -lower-global-dtors-via-cxa-atexit fallback flag
-  // (LowerGlobalDtorsViaCxaAtExit) and always issue a fatal error here.
-  if (TM->Options.LowerGlobalDtorsViaCxaAtExit)
-    report_fatal_error("@llvm.global_dtors should have been lowered already");
-  return StaticDtorSection;
+  report_fatal_error("@llvm.global_dtors should have been lowered already");
 }
 
 void TargetLoweringObjectFileMachO::emitModuleMetadata(MCStreamer &Streamer,

diff --git a/llvm/lib/CodeGen/TargetPassConfig.cpp b/llvm/lib/CodeGen/TargetPassConfig.cpp
index c48b520..32fa6cc 100644 (file)
--- a/llvm/lib/CodeGen/TargetPassConfig.cpp
+++ b/llvm/lib/CodeGen/TargetPassConfig.cpp
@@ -878,8 +878,7 @@ void TargetPassConfig::addIRPasses() {
 
   // For MachO, lower @llvm.global_dtors into @llvm.global_ctors with
   // __cxa_atexit() calls to avoid emitting the deprecated __mod_term_func.
-  if (TM->getTargetTriple().isOSBinFormatMachO() &&
-      TM->Options.LowerGlobalDtorsViaCxaAtExit)
+  if (TM->getTargetTriple().isOSBinFormatMachO())
     addPass(createLowerGlobalDtorsLegacyPass());
 
   // Make sure that no unreachable blocks are instruction selected.

diff --git a/llvm/test/CodeGen/ARM/ctors_dtors.ll b/llvm/test/CodeGen/ARM/ctors_dtors.ll
index b85d5c9..066c250 100644 (file)
--- a/llvm/test/CodeGen/ARM/ctors_dtors.ll
+++ b/llvm/test/CodeGen/ARM/ctors_dtors.ll
@@ -1,5 +1,4 @@
 ; RUN: llc < %s -mtriple=arm-apple-darwin  | FileCheck %s -check-prefix=DARWIN
-; RUN: llc < %s -mtriple=arm-apple-darwin -lower-global-dtors-via-cxa-atexit=false  | FileCheck %s -check-prefix=DARWIN-OLD
 ; RUN: llc < %s -mtriple=arm-linux-gnu -target-abi=apcs  | FileCheck %s -check-prefix=ELF
 ; RUN: llc < %s -mtriple=arm-linux-gnueabi | FileCheck %s -check-prefix=GNUEABI
 
@@ -8,9 +7,6 @@
 ; DARWIN: .section     __DATA,__mod_init_func,mod_init_funcs
 ; DARWIN-NOT: __mod_term_func
 
-; DARWIN-OLD: .section __DATA,__mod_init_func,mod_init_funcs
-; DARWIN-OLD: .section __DATA,__mod_term_func,mod_term_funcs
-
 ; ELF: .section .ctors,"aw",%progbits
 ; ELF: .section .dtors,"aw",%progbits