Revert "[SFrames] Emit and relax FREs (llvm#158154)" (llvm#159436)

Sterling-Augustine · web-flow · commit 6c8fcd6089b9 · 2025-09-17T13:26:20.000-07:00
Breaks some buildbots This reverts commit c928516.
diff --git a/llvm/include/llvm/BinaryFormat/SFrame.h b/llvm/include/llvm/BinaryFormat/SFrame.h
@@ -117,7 +117,6 @@ template <endianness E> struct FDEInfo {
     Info = ((PAuthKey & 1) << 5) | ((static_cast<uint8_t>(FDE) & 1) << 4) |
            (static_cast<uint8_t>(FRE) & 0xf);
   }
-  uint8_t getFuncInfo() const { return Info; }
 };
 
 template <endianness E> struct FuncDescEntry {
@@ -156,7 +155,6 @@ template <endianness E> struct FREInfo {
     Info = ((RA & 1) << 7) | ((static_cast<uint8_t>(Sz) & 3) << 5) |
            ((N & 0xf) << 1) | (static_cast<uint8_t>(Reg) & 1);
   }
-  uint8_t getFREInfo() const { return Info; }
 };
 
 template <typename T, endianness E> struct FrameRowEntry {
diff --git a/llvm/include/llvm/MC/MCAsmBackend.h b/llvm/include/llvm/MC/MCAsmBackend.h
@@ -168,7 +168,6 @@ class LLVM_ABI MCAsmBackend {
   virtual bool relaxAlign(MCFragment &F, unsigned &Size) { return false; }
   virtual bool relaxDwarfLineAddr(MCFragment &) const { return false; }
   virtual bool relaxDwarfCFA(MCFragment &) const { return false; }
-  virtual bool relaxSFrameCFA(MCFragment &) const { return false; }
 
   // Defined by linker relaxation targets to possibly emit LEB128 relocations
   // and set Value at the relocated location.
diff --git a/llvm/include/llvm/MC/MCAssembler.h b/llvm/include/llvm/MC/MCAssembler.h
@@ -117,7 +117,6 @@ class MCAssembler {
   void relaxBoundaryAlign(MCBoundaryAlignFragment &BF);
   void relaxDwarfLineAddr(MCFragment &F);
   void relaxDwarfCallFrameFragment(MCFragment &F);
-  void relaxSFrameFragment(MCFragment &DF);
 
 public:
   /// Construct a new assembler instance.
diff --git a/llvm/include/llvm/MC/MCObjectStreamer.h b/llvm/include/llvm/MC/MCObjectStreamer.h
@@ -150,9 +150,6 @@ class MCObjectStreamer : public MCStreamer {
                              MCSymbol *EndLabel = nullptr) override;
   void emitDwarfAdvanceFrameAddr(const MCSymbol *LastLabel,
                                  const MCSymbol *Label, SMLoc Loc);
-  void emitSFrameCalculateFuncOffset(const MCSymbol *FunCabsel,
-                                     const MCSymbol *FREBegin,
-                                     MCFragment *FDEFrag, SMLoc Loc);
   void emitCVLocDirective(unsigned FunctionId, unsigned FileNo, unsigned Line,
                           unsigned Column, bool PrologueEnd, bool IsStmt,
                           StringRef FileName, SMLoc Loc) override;
diff --git a/llvm/include/llvm/MC/MCSFrame.h b/llvm/include/llvm/MC/MCSFrame.h
@@ -16,30 +16,16 @@
 #ifndef LLVM_MC_MCSFRAME_H
 #define LLVM_MC_MCSFRAME_H
 
-#include "llvm/ADT/SmallVector.h"
-#include <cstdint>
-
 namespace llvm {
 
-class MCContext;
 class MCObjectStreamer;
-class MCFragment;
 
 class MCSFrameEmitter {
 public:
   // Emit the sframe section.
   //
   // \param Streamer - Emit into this stream.
   static void emit(MCObjectStreamer &Streamer);
-
-  // Encode the FRE's function offset.
-  //
-  // \param C - Context.
-  // \param Offset - Offset to encode.
-  // \param Out - Destination of the encoding.
-  // \param FDEFrag - Frag that specifies the encoding format.
-  static void encodeFuncOffset(MCContext &C, uint64_t Offset,
-                               SmallVectorImpl<char> &Out, MCFragment *FDEFrag);
 };
 
 } // end namespace llvm
diff --git a/llvm/include/llvm/MC/MCSection.h b/llvm/include/llvm/MC/MCSection.h
@@ -59,7 +59,6 @@ class MCFragment {
     FT_Org,
     FT_Dwarf,
     FT_DwarfFrame,
-    FT_SFrame,
     FT_BoundaryAlign,
     FT_SymbolId,
     FT_CVInlineLines,
@@ -144,12 +143,6 @@ class MCFragment {
       // .loc dwarf directives.
       int64_t LineDelta;
     } dwarf;
-    struct {
-      // This FRE describes unwind info at AddrDelta from function start.
-      const MCExpr *AddrDelta;
-      // Fragment that records how many bytes of AddrDelta to emit.
-      MCFragment *FDEFragment;
-    } sframe;
   } u{};
 
 public:
@@ -303,24 +296,6 @@ class MCFragment {
     assert(Kind == FT_Dwarf);
     u.dwarf.LineDelta = LineDelta;
   }
-
-  //== FT_SFrame functions
-  const MCExpr &getSFrameAddrDelta() const {
-    assert(Kind == FT_SFrame);
-    return *u.sframe.AddrDelta;
-  }
-  void setSFrameAddrDelta(const MCExpr *E) {
-    assert(Kind == FT_SFrame);
-    u.sframe.AddrDelta = E;
-  }
-  MCFragment *getSFrameFDE() const {
-    assert(Kind == FT_SFrame);
-    return u.sframe.FDEFragment;
-  }
-  void setSFrameFDE(MCFragment *F) {
-    assert(Kind == FT_SFrame);
-    u.sframe.FDEFragment = F;
-  }
 };
 
 // MCFragment subclasses do not use the fixed-size part or variable-size tail of
diff --git a/llvm/lib/MC/MCAssembler.cpp b/llvm/lib/MC/MCAssembler.cpp
@@ -22,7 +22,6 @@
 #include "llvm/MC/MCFixup.h"
 #include "llvm/MC/MCInst.h"
 #include "llvm/MC/MCObjectWriter.h"
-#include "llvm/MC/MCSFrame.h"
 #include "llvm/MC/MCSection.h"
 #include "llvm/MC/MCSymbol.h"
 #include "llvm/MC/MCValue.h"
@@ -200,7 +199,6 @@ uint64_t MCAssembler::computeFragmentSize(const MCFragment &F) const {
   case MCFragment::FT_LEB:
   case MCFragment::FT_Dwarf:
   case MCFragment::FT_DwarfFrame:
-  case MCFragment::FT_SFrame:
   case MCFragment::FT_CVInlineLines:
   case MCFragment::FT_CVDefRange:
     return F.getSize();
@@ -401,7 +399,6 @@ static void writeFragment(raw_ostream &OS, const MCAssembler &Asm,
   case MCFragment::FT_LEB:
   case MCFragment::FT_Dwarf:
   case MCFragment::FT_DwarfFrame:
-  case MCFragment::FT_SFrame:
   case MCFragment::FT_CVInlineLines:
   case MCFragment::FT_CVDefRange: {
     if (F.getKind() == MCFragment::FT_Data)
@@ -917,24 +914,6 @@ void MCAssembler::relaxDwarfCallFrameFragment(MCFragment &F) {
   F.clearVarFixups();
 }
 
-void MCAssembler::relaxSFrameFragment(MCFragment &F) {
-  assert(F.getKind() == MCFragment::FT_SFrame);
-  MCContext &C = getContext();
-  int64_t Value;
-  bool Abs = F.getSFrameAddrDelta().evaluateAsAbsolute(Value, *this);
-  if (!Abs) {
-    C.reportError(F.getSFrameAddrDelta().getLoc(),
-                  "invalid CFI advance_loc expression in sframe");
-    F.setSFrameAddrDelta(MCConstantExpr::create(0, C));
-    return;
-  }
-
-  SmallVector<char, 4> Data;
-  MCSFrameEmitter::encodeFuncOffset(Context, Value, Data, F.getSFrameFDE());
-  F.setVarContents(Data);
-  F.clearVarFixups();
-}
-
 bool MCAssembler::relaxFragment(MCFragment &F) {
   auto Size = computeFragmentSize(F);
   switch (F.getKind()) {
@@ -953,9 +932,6 @@ bool MCAssembler::relaxFragment(MCFragment &F) {
   case MCFragment::FT_DwarfFrame:
     relaxDwarfCallFrameFragment(F);
     break;
-  case MCFragment::FT_SFrame:
-    relaxSFrameFragment(F);
-    break;
   case MCFragment::FT_BoundaryAlign:
     relaxBoundaryAlign(static_cast<MCBoundaryAlignFragment &>(F));
     break;
diff --git a/llvm/lib/MC/MCFragment.cpp b/llvm/lib/MC/MCFragment.cpp
@@ -53,7 +53,6 @@ LLVM_DUMP_METHOD void MCFragment::dump() const {
   case MCFragment::FT_Org:           OS << "Org"; break;
   case MCFragment::FT_Dwarf:         OS << "Dwarf"; break;
   case MCFragment::FT_DwarfFrame:    OS << "DwarfCallFrame"; break;
-  case MCFragment::FT_SFrame:        OS << "SFrame"; break;
   case MCFragment::FT_LEB:           OS << "LEB"; break;
   case MCFragment::FT_BoundaryAlign: OS<<"BoundaryAlign"; break;
   case MCFragment::FT_SymbolId:      OS << "SymbolId"; break;
@@ -80,8 +79,7 @@ LLVM_DUMP_METHOD void MCFragment::dump() const {
   case MCFragment::FT_Align:
   case MCFragment::FT_LEB:
   case MCFragment::FT_Dwarf:
-  case MCFragment::FT_DwarfFrame:
-  case MCFragment::FT_SFrame: {
+  case MCFragment::FT_DwarfFrame: {
     if (isLinkerRelaxable())
       OS << " LinkerRelaxable";
     auto Fixed = getContents();
@@ -131,7 +129,6 @@ LLVM_DUMP_METHOD void MCFragment::dump() const {
       OS << " LineDelta:" << getDwarfLineDelta();
       break;
     case MCFragment::FT_DwarfFrame:
-    case MCFragment::FT_SFrame:
       OS << " AddrDelta:";
       getDwarfAddrDelta().print(OS, nullptr);
       break;
diff --git a/llvm/lib/MC/MCObjectStreamer.cpp b/llvm/lib/MC/MCObjectStreamer.cpp
@@ -583,19 +583,6 @@ void MCObjectStreamer::emitDwarfAdvanceFrameAddr(const MCSymbol *LastLabel,
   newFragment();
 }
 
-void MCObjectStreamer::emitSFrameCalculateFuncOffset(const MCSymbol *FuncBase,
-                                                     const MCSymbol *FREBegin,
-                                                     MCFragment *FDEFrag,
-                                                     SMLoc Loc) {
-  assert(FuncBase && "No function base address");
-  assert(FREBegin && "FRE doesn't describe a location");
-  auto *F = getCurrentFragment();
-  F->Kind = MCFragment::FT_SFrame;
-  F->setSFrameAddrDelta(buildSymbolDiff(*this, FREBegin, FuncBase, Loc));
-  F->setSFrameFDE(FDEFrag);
-  newFragment();
-}
-
 void MCObjectStreamer::emitCVLocDirective(unsigned FunctionId, unsigned FileNo,
                                           unsigned Line, unsigned Column,
                                           bool PrologueEnd, bool IsStmt,
diff --git a/llvm/lib/MC/MCSFrame.cpp b/llvm/lib/MC/MCSFrame.cpp
diff --git a/llvm/test/MC/ELF/cfi-sframe-encoding.s b/llvm/test/MC/ELF/cfi-sframe-encoding.s
diff --git a/llvm/test/MC/ELF/cfi-sframe-fre-cases.s b/llvm/test/MC/ELF/cfi-sframe-fre-cases.s
diff --git a/llvm/test/MC/ELF/cfi-sframe.s b/llvm/test/MC/ELF/cfi-sframe.s

Original file line number	Diff line number	Diff line change
`@@ -117,7 +117,6 @@ template <endianness E> struct FDEInfo {`
`117`	`117`	`Info = ((PAuthKey & 1) << 5) \| ((static_cast<uint8_t>(FDE) & 1) << 4) \|`
`118`	`118`	`(static_cast<uint8_t>(FRE) & 0xf);`
`119`	`119`	`}`
`120`		`- uint8_t getFuncInfo() const { return Info; }`
`121`	`120`	`};`
`122`	`121`
`123`	`122`	`template <endianness E> struct FuncDescEntry {`
`@@ -156,7 +155,6 @@ template <endianness E> struct FREInfo {`
`156`	`155`	`Info = ((RA & 1) << 7) \| ((static_cast<uint8_t>(Sz) & 3) << 5) \|`
`157`	`156`	`((N & 0xf) << 1) \| (static_cast<uint8_t>(Reg) & 1);`
`158`	`157`	`}`
`159`		`- uint8_t getFREInfo() const { return Info; }`
`160`	`158`	`};`
`161`	`159`
`162`	`160`	`template <typename T, endianness E> struct FrameRowEntry {`