Reapply "Support SFrame command-line and .cfi_section syntax (llvm#150316) (llvm#150509)

Sterling-Augustine · mahesh-attarde · commit 72d5f5afccb6 · 2025-07-28T04:21:46.000-07:00
This reverts commit ad36e42, fixing a single uninitialized bit (which cannot be detected with Address Sanitizer). This PR adds support for the llvm-mc command-line flag "--gsframe" and adds ".sframe" to the legal values passed ".cfi_section". It plumbs the option through the cfi handling code a fair amount. Code to support actual section generation follows in a future PR. These options match the gnu-assembler's support syntax for sframes, on both the command line and in assembly files. First in a series of changes that will allow llvm-mc to produce sframe .cfi sections. For more information about sframes, see https://sourceware.org/binutils/docs-2.44/sframe-spec.html and the llvm-RFC here: https://discourse.llvm.org/t/rfc-adding-sframe-support-to-llvm/86900
diff --git a/llvm/include/llvm/MC/MCObjectStreamer.h b/llvm/include/llvm/MC/MCObjectStreamer.h
@@ -40,6 +40,7 @@ class MCObjectStreamer : public MCStreamer {
   std::unique_ptr<MCAssembler> Assembler;
   bool EmitEHFrame;
   bool EmitDebugFrame;
+  bool EmitSFrame;
 
   struct PendingAssignment {
     MCSymbol *Symbol;
@@ -70,7 +71,7 @@ class MCObjectStreamer : public MCStreamer {
 
   void emitFrames(MCAsmBackend *MAB);
   MCSymbol *emitCFILabel() override;
-  void emitCFISections(bool EH, bool Debug) override;
+  void emitCFISections(bool EH, bool Debug, bool SFrame) override;
 
 public:
   void visitUsedSymbol(const MCSymbol &Sym) override;
diff --git a/llvm/include/llvm/MC/MCStreamer.h b/llvm/include/llvm/MC/MCStreamer.h
@@ -986,7 +986,7 @@ class LLVM_ABI MCStreamer {
                                                const MCSymbol *Lo);
 
   virtual MCSymbol *getDwarfLineTableSymbol(unsigned CUID);
-  virtual void emitCFISections(bool EH, bool Debug);
+  virtual void emitCFISections(bool EH, bool Debug, bool SFrame);
   void emitCFIStartProc(bool IsSimple, SMLoc Loc = SMLoc());
   void emitCFIEndProc();
   virtual void emitCFIDefCfa(int64_t Register, int64_t Offset, SMLoc Loc = {});
diff --git a/llvm/include/llvm/MC/MCTargetOptions.h b/llvm/include/llvm/MC/MCTargetOptions.h
@@ -102,6 +102,9 @@ class MCTargetOptions {
   // functions on Darwins.
   bool EmitCompactUnwindNonCanonical : 1;
 
+  // Whether to emit SFrame unwind sections.
+  bool EmitSFrameUnwind : 1;
+
   // Whether or not to use full register names on PowerPC.
   bool PPCUseFullRegisterNames : 1;
 
diff --git a/llvm/include/llvm/MC/MCTargetOptionsCommandFlags.h b/llvm/include/llvm/MC/MCTargetOptionsCommandFlags.h
@@ -40,6 +40,8 @@ LLVM_ABI EmitDwarfUnwindType getEmitDwarfUnwind();
 
 LLVM_ABI bool getEmitCompactUnwindNonCanonical();
 
+LLVM_ABI bool getEmitSFrameUnwind();
+
 LLVM_ABI bool getShowMCInst();
 
 LLVM_ABI bool getFatalWarnings();
diff --git a/llvm/lib/CodeGen/AsmPrinter/ARMException.cpp b/llvm/lib/CodeGen/AsmPrinter/ARMException.cpp
@@ -39,7 +39,7 @@ void ARMException::beginFunction(const MachineFunction *MF) {
   if (CFISecType == AsmPrinter::CFISection::Debug) {
     if (!hasEmittedCFISections) {
       if (Asm->getModuleCFISectionType() == AsmPrinter::CFISection::Debug)
-        Asm->OutStreamer->emitCFISections(false, true);
+        Asm->OutStreamer->emitCFISections(false, true, false);
       hasEmittedCFISections = true;
     }
 
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfCFIException.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfCFIException.cpp
@@ -109,9 +109,11 @@ void DwarfCFIException::beginBasicBlockSection(const MachineBasicBlock &MBB) {
     // chose not to be verbose in that case. And with `ForceDwarfFrameSection`,
     // we should always emit .debug_frame.
     if (CFISecType == AsmPrinter::CFISection::Debug ||
-        Asm->TM.Options.ForceDwarfFrameSection)
+        Asm->TM.Options.ForceDwarfFrameSection ||
+        Asm->TM.Options.MCOptions.EmitSFrameUnwind)
       Asm->OutStreamer->emitCFISections(
-          CFISecType == AsmPrinter::CFISection::EH, true);
+          CFISecType == AsmPrinter::CFISection::EH, true,
+          Asm->TM.Options.MCOptions.EmitSFrameUnwind);
     hasEmittedCFISections = true;
   }
 
diff --git a/llvm/lib/MC/MCAsmStreamer.cpp b/llvm/lib/MC/MCAsmStreamer.cpp
@@ -345,7 +345,7 @@ class MCAsmStreamer final : public MCStreamer {
   void emitIdent(StringRef IdentString) override;
   void emitCFIBKeyFrame() override;
   void emitCFIMTETaggedFrame() override;
-  void emitCFISections(bool EH, bool Debug) override;
+  void emitCFISections(bool EH, bool Debug, bool SFrame) override;
   void emitCFIDefCfa(int64_t Register, int64_t Offset, SMLoc Loc) override;
   void emitCFIDefCfaOffset(int64_t Offset, SMLoc Loc) override;
   void emitCFIDefCfaRegister(int64_t Register, SMLoc Loc) override;
@@ -1906,15 +1906,24 @@ void MCAsmStreamer::emitIdent(StringRef IdentString) {
   EmitEOL();
 }
 
-void MCAsmStreamer::emitCFISections(bool EH, bool Debug) {
-  MCStreamer::emitCFISections(EH, Debug);
+void MCAsmStreamer::emitCFISections(bool EH, bool Debug, bool SFrame) {
+  MCStreamer::emitCFISections(EH, Debug, SFrame);
   OS << "\t.cfi_sections ";
+  bool C = false;
   if (EH) {
     OS << ".eh_frame";
-    if (Debug)
-      OS << ", .debug_frame";
-  } else if (Debug) {
+    C = true;
+  }
+  if (Debug) {
+    if (C)
+      OS << ", ";
     OS << ".debug_frame";
+    C = true;
+  }
+  if (SFrame) {
+    if (C)
+      OS << ", ";
+    OS << ".sframe";
   }
 
   EmitEOL();
diff --git a/llvm/lib/MC/MCObjectStreamer.cpp b/llvm/lib/MC/MCObjectStreamer.cpp
@@ -129,10 +129,11 @@ void MCObjectStreamer::visitUsedSymbol(const MCSymbol &Sym) {
   Assembler->registerSymbol(Sym);
 }
 
-void MCObjectStreamer::emitCFISections(bool EH, bool Debug) {
-  MCStreamer::emitCFISections(EH, Debug);
+void MCObjectStreamer::emitCFISections(bool EH, bool Debug, bool SFrame) {
+  MCStreamer::emitCFISections(EH, Debug, SFrame);
   EmitEHFrame = EH;
   EmitDebugFrame = Debug;
+  EmitSFrame = SFrame;
 }
 
 void MCObjectStreamer::emitValueImpl(const MCExpr *Value, unsigned Size,
diff --git a/llvm/lib/MC/MCParser/AsmParser.cpp b/llvm/lib/MC/MCParser/AsmParser.cpp
@@ -4093,27 +4093,30 @@ bool AsmParser::parseDirectiveCVFPOData() {
 }
 
 /// parseDirectiveCFISections
-/// ::= .cfi_sections section [, section]
+/// ::= .cfi_sections section [, section][, section]
 bool AsmParser::parseDirectiveCFISections() {
   StringRef Name;
   bool EH = false;
   bool Debug = false;
+  bool SFrame = false;
 
   if (!parseOptionalToken(AsmToken::EndOfStatement)) {
     for (;;) {
       if (parseIdentifier(Name))
-        return TokError("expected .eh_frame or .debug_frame");
+        return TokError("expected .eh_frame, .debug_frame, or .sframe");
       if (Name == ".eh_frame")
         EH = true;
       else if (Name == ".debug_frame")
         Debug = true;
+      else if (Name == ".sframe")
+        SFrame = true;
       if (parseOptionalToken(AsmToken::EndOfStatement))
         break;
       if (parseComma())
         return true;
     }
   }
-  getStreamer().emitCFISections(EH, Debug);
+  getStreamer().emitCFISections(EH, Debug, SFrame);
   return false;
 }
 
diff --git a/llvm/lib/MC/MCStreamer.cpp b/llvm/lib/MC/MCStreamer.cpp
@@ -415,7 +415,7 @@ void MCStreamer::emitLabel(MCSymbol *Symbol, SMLoc Loc) {
 void MCStreamer::emitConditionalAssignment(MCSymbol *Symbol,
                                            const MCExpr *Value) {}
 
-void MCStreamer::emitCFISections(bool EH, bool Debug) {}
+void MCStreamer::emitCFISections(bool EH, bool Debug, bool SFrame) {}
 
 void MCStreamer::emitCFIStartProc(bool IsSimple, SMLoc Loc) {
   if (!FrameInfoStack.empty() &&
diff --git a/llvm/lib/MC/MCTargetOptions.cpp b/llvm/lib/MC/MCTargetOptions.cpp
@@ -19,7 +19,8 @@ MCTargetOptions::MCTargetOptions()
       PreserveAsmComments(true), Dwarf64(false),
       EmitDwarfUnwind(EmitDwarfUnwindType::Default),
       MCUseDwarfDirectory(DefaultDwarfDirectory),
-      EmitCompactUnwindNonCanonical(false), PPCUseFullRegisterNames(false) {}
+      EmitCompactUnwindNonCanonical(false), EmitSFrameUnwind(false),
+      PPCUseFullRegisterNames(false) {}
 
 StringRef MCTargetOptions::getABIName() const {
   return ABIName;
diff --git a/llvm/lib/MC/MCTargetOptionsCommandFlags.cpp b/llvm/lib/MC/MCTargetOptionsCommandFlags.cpp
@@ -41,6 +41,7 @@ MCOPT(int, DwarfVersion)
 MCOPT(bool, Dwarf64)
 MCOPT(EmitDwarfUnwindType, EmitDwarfUnwind)
 MCOPT(bool, EmitCompactUnwindNonCanonical)
+MCOPT(bool, EmitSFrameUnwind)
 MCOPT(bool, ShowMCInst)
 MCOPT(bool, FatalWarnings)
 MCOPT(bool, NoWarn)
@@ -105,6 +106,11 @@ llvm::mc::RegisterMCTargetOptionsFlags::RegisterMCTargetOptionsFlags() {
           false)); // By default, use DWARF for non-canonical personalities.
   MCBINDOPT(EmitCompactUnwindNonCanonical);
 
+  static cl::opt<bool> EmitSFrameUnwind(
+      "gsframe", cl::desc("Whether to emit .sframe unwind sections."),
+      cl::init(false));
+  MCBINDOPT(EmitSFrameUnwind);
+
   static cl::opt<bool> ShowMCInst(
       "asm-show-inst",
       cl::desc("Emit internal instruction representation to assembly file"));
@@ -188,6 +194,7 @@ MCTargetOptions llvm::mc::InitMCTargetOptionsFromFlags() {
   Options.X86Sse2Avx = getX86Sse2Avx();
   Options.EmitDwarfUnwind = getEmitDwarfUnwind();
   Options.EmitCompactUnwindNonCanonical = getEmitCompactUnwindNonCanonical();
+  Options.EmitSFrameUnwind = getEmitSFrameUnwind();
   Options.AsSecureLogFile = getAsSecureLogFile();
 
   return Options;
diff --git a/llvm/test/MC/ELF/AArch64/cfi.s b/llvm/test/MC/ELF/AArch64/cfi.s
@@ -557,12 +557,14 @@ f37:
 // CHECK-NEXT:  }
 
 .ifdef ERR
-// ERR: [[#@LINE+1]]:15: error: expected .eh_frame or .debug_frame
+// ERR: [[#@LINE+1]]:15: error: expected .eh_frame, .debug_frame, or .sframe
 .cfi_sections $
 // ERR: [[#@LINE+1]]:28: error: expected comma
 .cfi_sections .debug_frame $
 // ERR: [[#@LINE+1]]:39: error: expected comma
 .cfi_sections .debug_frame, .eh_frame $
+// ERR: [[#@LINE+1]]:48: error: expected comma
+.cfi_sections .debug_frame, .eh_frame, .sframe $
 
 // ERR: [[#@LINE+1]]:16: error: unexpected token
 .cfi_startproc $
diff --git a/llvm/test/MC/ELF/cfi.s b/llvm/test/MC/ELF/cfi.s
@@ -445,12 +445,14 @@ f37:
 // CHECK:        }
 
 .ifdef ERR
-// ERR: [[#@LINE+1]]:15: error: expected .eh_frame or .debug_frame
+// ERR: [[#@LINE+1]]:15: error: expected .eh_frame, .debug_frame, or .sframe
 .cfi_sections $
 // ERR: [[#@LINE+1]]:28: error: expected comma
 .cfi_sections .debug_frame $
 // ERR: [[#@LINE+1]]:39: error: expected comma
 .cfi_sections .debug_frame, .eh_frame $
+// ERR: [[#@LINE+1]]:48: error: expected comma
+.cfi_sections .debug_frame, .eh_frame, .sframe $
 
 // ERR: [[#@LINE+1]]:16: error: unexpected token
 .cfi_startproc $

Original file line number	Diff line number	Diff line change
`@@ -39,7 +39,7 @@ void ARMException::beginFunction(const MachineFunction *MF) {`
`39`	`39`	`if (CFISecType == AsmPrinter::CFISection::Debug) {`
`40`	`40`	`if (!hasEmittedCFISections) {`
`41`	`41`	`if (Asm->getModuleCFISectionType() == AsmPrinter::CFISection::Debug)`
`42`		`- Asm->OutStreamer->emitCFISections(false, true);`
	`42`	`+ Asm->OutStreamer->emitCFISections(false, true, false);`
`43`	`43`	`hasEmittedCFISections = true;`
`44`	`44`	`}`
`45`	`45`
Original file line number	Diff line number	Diff line change
`@@ -129,10 +129,11 @@ void MCObjectStreamer::visitUsedSymbol(const MCSymbol &Sym) {`
`129`	`129`	`Assembler->registerSymbol(Sym);`
`130`	`130`	`}`
`131`	`131`
`132`		`-void MCObjectStreamer::emitCFISections(bool EH, bool Debug) {`
`133`		`- MCStreamer::emitCFISections(EH, Debug);`
	`132`	`+void MCObjectStreamer::emitCFISections(bool EH, bool Debug, bool SFrame) {`
	`133`	`+ MCStreamer::emitCFISections(EH, Debug, SFrame);`
`134`	`134`	`EmitEHFrame = EH;`
`135`	`135`	`EmitDebugFrame = Debug;`
	`136`	`+ EmitSFrame = SFrame;`
`136`	`137`	`}`
`137`	`138`
`138`	`139`	`void MCObjectStreamer::emitValueImpl(const MCExpr *Value, unsigned Size,`