Emit .cfi_sections before the first .cfi_startproc

[joerg]

Summary

GNU as rejects input where .cfi_sections is used after .cfi_startproc, if the new section differs from the old. Adjust our output to always emit .cfi_sections before the first .cfi_startproc to minimize necessary code.

[majnemer]

LGTM, I'd name it hasEmittedCFISections

Should/do we reject this in the parser?

lib/CodeGen/AsmPrinter/ARMException.cpp

 
 ARMException::~ARMException() {}
 
 ARMTargetStreamer &ARMException::getTargetStreamer() {
   MCTargetStreamer &TS = *Asm->OutStreamer->getTargetStreamer();
   return static_cast<ARMTargetStreamer &>(TS);
 }
 
-/// endModule - Emit all exception information that should come after the
-/// content.
-void ARMException::endModule() {
-  if (shouldEmitCFI)
-    Asm->OutStreamer->EmitCFISections(false, true);
-}
-
 void ARMException::beginFunction(const MachineFunction *MF) {
   if (Asm->MAI->getExceptionHandlingType() == ExceptionHandling::ARM)
     getTargetStreamer().emitFnStart();
   // See if we need call frame info.
   AsmPrinter::CFIMoveType MoveType = Asm->needsCFIMoves();
   assert(MoveType != AsmPrinter::CFI_M_EH &&
          "non-EH CFI not yet supported in prologue with EHABI lowering");
+
   if (MoveType == AsmPrinter::CFI_M_Debug) {
+    if (!hasEmittedCFI) {
+      Asm->OutStreamer->EmitCFISections(false, true);
+      hasEmittedCFI = true;
+    }
+
     shouldEmitCFI = true;
     Asm->OutStreamer->EmitCFIStartProc(false);
   }
 }
 
 /// endFunction - Gather and emit post-function exception information.
 ///
 void ARMException::endFunction(const MachineFunction *MF) {

lib/CodeGen/AsmPrinter/DwarfCFIException.cpp

 #include "llvm/Target/TargetFrameLowering.h"
 #include "llvm/Target/TargetLoweringObjectFile.h"
 #include "llvm/Target/TargetMachine.h"
 #include "llvm/Target/TargetOptions.h"
 #include "llvm/Target/TargetRegisterInfo.h"
 using namespace llvm;
 
 DwarfCFIExceptionBase::DwarfCFIExceptionBase(AsmPrinter *A)
-    : EHStreamer(A), shouldEmitCFI(false) {}
+    : EHStreamer(A), shouldEmitCFI(false), hasEmittedCFI(false) {}
 
 void DwarfCFIExceptionBase::markFunctionEnd() {
   endFragment();
 
   // Map all labels and get rid of any dead landing pads.
   if (!Asm->MF->getLandingPads().empty()) {
     MachineFunction *NonConstMF = const_cast<MachineFunction*>(Asm->MF);
     NonConstMF->tidyLandingPads();
   }
 }
 
 void DwarfCFIExceptionBase::endFragment() {
   if (shouldEmitCFI)
     Asm->OutStreamer->EmitCFIEndProc();
 }
 
 DwarfCFIException::DwarfCFIException(AsmPrinter *A)
     : DwarfCFIExceptionBase(A), shouldEmitPersonality(false),
       forceEmitPersonality(false), shouldEmitLSDA(false),
-      shouldEmitMoves(false), moveTypeModule(AsmPrinter::CFI_M_None) {}
+      shouldEmitMoves(false) {}
 
 DwarfCFIException::~DwarfCFIException() {}
 
 /// endModule - Emit all exception information that should come after the
 /// content.
 void DwarfCFIException::endModule() {
   // SjLj uses this pass and it doesn't need this info.
   if (!Asm->MAI->usesCFIForEH())
     return;
 
-  if (moveTypeModule == AsmPrinter::CFI_M_Debug)
-    Asm->OutStreamer->EmitCFISections(false, true);
-
   const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();
 
   unsigned PerEncoding = TLOF.getPersonalityEncoding();
 
   if ((PerEncoding & 0x80) != dwarf::DW_EH_PE_indirect)
     return;
 
   // Emit references to all used personality functions
void DwarfCFIException::beginFunction(const MachineFunction *MF) {
   shouldEmitMoves = shouldEmitPersonality = shouldEmitLSDA = false;
   const Function *F = MF->getFunction();
 
   // If any landing pads survive, we need an EH table.
   bool hasLandingPads = !MF->getLandingPads().empty();
 
   // See if we need frame move info.
   AsmPrinter::CFIMoveType MoveType = Asm->needsCFIMoves();
-  if (MoveType == AsmPrinter::CFI_M_EH ||
-      (MoveType == AsmPrinter::CFI_M_Debug &&
-       moveTypeModule == AsmPrinter::CFI_M_None))
-    moveTypeModule = MoveType;
 
   shouldEmitMoves = MoveType != AsmPrinter::CFI_M_None;
 
   const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();
   unsigned PerEncoding = TLOF.getPersonalityEncoding();
   const Function *Per = nullptr;
   if (F->hasPersonalityFn())
     Per = dyn_cast<Function>(F->getPersonalityFn()->stripPointerCasts());
void DwarfCFIException::beginFunction(const MachineFunction *MF) {
   beginFragment(&*MF->begin(), getExceptionSym);
 }
 
 void DwarfCFIException::beginFragment(const MachineBasicBlock *MBB,
                                       ExceptionSymbolProvider ESP) {
   if (!shouldEmitCFI)
     return;
 
+  if (!hasEmittedCFI) {
+    if (Asm->needsCFIMoves() == AsmPrinter::CFI_M_Debug)
+      Asm->OutStreamer->EmitCFISections(false, true);
+    hasEmittedCFI = true;
+  }
+
   Asm->OutStreamer->EmitCFIStartProc(/*IsSimple=*/false);
 
   // Indicate personality routine, if any.
   if (!shouldEmitPersonality)
     return;
 
   auto *F = MBB->getParent()->getFunction();
   auto *P = dyn_cast<Function>(F->getPersonalityFn()->stripPointerCasts());

lib/CodeGen/AsmPrinter/DwarfException.h

 class ARMTargetStreamer;
 
 class LLVM_LIBRARY_VISIBILITY DwarfCFIExceptionBase : public EHStreamer {
 protected:
   DwarfCFIExceptionBase(AsmPrinter *A);
 
   /// Per-function flag to indicate if frame CFI info should be emitted.
   bool shouldEmitCFI;
+  /// Per-module flag to indicate if .cfi_section has beeen emitted.
+  bool hasEmittedCFI;
 
   void markFunctionEnd() override;
   void endFragment() override;
 };
 
 class LLVM_LIBRARY_VISIBILITY DwarfCFIException : public DwarfCFIExceptionBase {
   /// Per-function flag to indicate if .cfi_personality should be emitted.
   bool shouldEmitPersonality;
 
   /// Per-function flag to indicate if .cfi_personality must be emitted.
   bool forceEmitPersonality;
 
   /// Per-function flag to indicate if .cfi_lsda should be emitted.
   bool shouldEmitLSDA;
 
   /// Per-function flag to indicate if frame moves info should be emitted.
   bool shouldEmitMoves;
 
-  AsmPrinter::CFIMoveType moveTypeModule;
-
 public:
   //===--------------------------------------------------------------------===//
   // Main entry points.
   //
   DwarfCFIException(AsmPrinter *A);
   ~DwarfCFIException() override;
 
   /// Emit all exception information that should come after the content.

 public:
   //===--------------------------------------------------------------------===//
   // Main entry points.
   //
   ARMException(AsmPrinter *A);
   ~ARMException() override;
 
   /// Emit all exception information that should come after the content.
-  void endModule() override;
+  void endModule() override {}
 
   /// Gather pre-function exception information.  Assumes being emitted
   /// immediately after the function entry point.
   void beginFunction(const MachineFunction *MF) override;
 
   /// Gather and emit post-function exception information.
   void endFunction(const MachineFunction *) override;
 };
 } // End of namespace llvm
 
 #endif

test/CodeGen/ARM/early-cfi-sections.ll

+; RUN: llc < %s | FileCheck %s
+; RUN: llc -mtriple=arm-netbsd-eabi < %s | FileCheck %s
+; CHECK-NOT: .cfi_startproc
+; CHECK:     .cfi_sections .debug_frame
+; CHECK:     .cfi_startproc
+
+target datalayout = "e-m:e-p:32:32-i64:64-v128:64:128-a:0:32-n32-S64"
+target triple = "armv4t--linux"
+
+; Function Attrs: nounwind
+define arm_aapcscc void @f() #0 !dbg !7 {
+entry:
+  ret void, !dbg !10
+}
+
+attributes #0 = { nounwind "correctly-rounded-divide-sqrt-fp-math"="false" "disable-tail-calls"="false" "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-jump-tables"="false" "no-nans-fp-math"="false" "no-signed-zeros-fp-math"="false" "no-trapping-math"="false" "stack-protector-buffer-size"="8" "target-cpu"="arm7tdmi" "target-features"="+soft-float,+strict-align,-crypto,-neon" "unsafe-fp-math"="false" "use-soft-float"="true" }
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!3, !4, !5, !6}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 4.0.0 (trunk 290216)", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !2)
+!1 = !DIFile(filename: "test.c", directory: "/tmp")
+!2 = !{}
+!3 = !{i32 2, !"Dwarf Version", i32 4}
+!4 = !{i32 2, !"Debug Info Version", i32 3}
+!5 = !{i32 1, !"wchar_size", i32 4}
+!6 = !{i32 1, !"min_enum_size", i32 4}
+!7 = distinct !DISubprogram(name: "f", scope: !1, file: !1, line: 1, type: !8, isLocal: false, isDefinition: true, scopeLine: 1, flags: DIFlagPrototyped, isOptimized: false, unit: !0, variables: !2)
+!8 = !DISubroutineType(types: !9)
+!9 = !{null}
+!10 = !DILocation(line: 1, column: 1, scope: !7)

test/CodeGen/ARM/no-cfi.ll

+; RUN: llc < %s | FileCheck %s
+; RUN: llc -mtriple=arm-netbsd-eabi < %s | FileCheck %s
+; CHECK-NOT: .cfi_startproc
+; CHECK-NOT: .cfi_sections
+
+target datalayout = "e-m:e-p:32:32-i64:64-v128:64:128-a:0:32-n32-S64"
+target triple = "armv4t--linux"
+
+@f = common global i32 0, align 4, !dbg !0
+
+!llvm.dbg.cu = !{!2}
+!llvm.module.flags = !{!7, !8, !9, !10}
+
+!0 = !DIGlobalVariableExpression(var: !1)
+!1 = distinct !DIGlobalVariable(name: "f", scope: !2, file: !3, line: 1, type: !6, isLocal: false, isDefinition: true)
+!2 = distinct !DICompileUnit(language: DW_LANG_C99, file: !3, producer: "clang version 4.0.0 (trunk 290216)", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !4, globals: !5)
+!3 = !DIFile(filename: "test2.c", directory: "/tmp")
+!4 = !{}
+!5 = !{!0}
+!6 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!7 = !{i32 2, !"Dwarf Version", i32 4}
+!8 = !{i32 2, !"Debug Info Version", i32 3}
+!9 = !{i32 1, !"wchar_size", i32 4}
+!10 = !{i32 1, !"min_enum_size", i32 4}

test/CodeGen/X86/early-cfi-sections.ll

+; RUN: llc < %s | FileCheck %s
+; CHECK-NOT: .cfi_startproc
+; CHECK:     .cfi_sections .debug_frame
+; CHECK:     .cfi_startproc
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+; Function Attrs: nounwind
+define void @f() #0 !dbg !5 {
+entry:
+  ret void, !dbg !8
+}
+
+attributes #0 = { nounwind "correctly-rounded-divide-sqrt-fp-math"="false" "disable-tail-calls"="false" "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-jump-tables"="false" "no-nans-fp-math"="false" "no-signed-zeros-fp-math"="false" "no-trapping-math"="false" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+fxsr,+mmx,+sse,+sse2,+x87" "unsafe-fp-math"="false" "use-soft-float"="false" }
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!3, !4}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 4.0.0 (trunk 290216)", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !2)
+!1 = !DIFile(filename: "test.c", directory: "/tmp")
+!2 = !{}
+!3 = !{i32 2, !"Dwarf Version", i32 4}
+!4 = !{i32 2, !"Debug Info Version", i32 3}
+!5 = distinct !DISubprogram(name: "f", scope: !1, file: !1, line: 1, type: !6, isLocal: false, isDefinition: true, scopeLine: 1, flags: DIFlagPrototyped, isOptimized: false, unit: !0, variables: !2)
+!6 = !DISubroutineType(types: !7)
+!7 = !{null}
+!8 = !DILocation(line: 1, column: 1, scope: !5)