[snippy] do not insert EH frame sections

llvm/include/llvm/MC/MCObjectStreamer.h

@@ -89,6 +89,12 @@ class MCObjectStreamer : public MCStreamer {
   void emitFrames(MCAsmBackend *MAB);
   void emitCFISections(bool EH, bool Debug) override;
 
+  bool setEmitEHFrame(bool Val) { return std::exchange(EmitEHFrame, Val); }
+
+  bool setEmitDebugFrame(bool Val) {
+    return std::exchange(EmitDebugFrame, Val);
+  }
+
   MCFragment *getCurrentFragment() const;
 
   void insert(MCFragment *F) {

llvm/test/tools/llvm-snippy/linker-script-layout.yaml

@@ -26,11 +26,11 @@ histogram:
     - [ADDI, 1.0]
     - [SW, 5.0]
 
-# UNMANGLED: SNIPPY (rwx) : ORIGIN = 65536, LENGTH = 67072
+# UNMANGLED: SNIPPY (rwx) : ORIGIN = 65536, LENGTH = 1536
 # UNMANGLED: .snippy.1.rx 65536: {
 # UNMANGLED: .snippy.2.rw 66048 (NOLOAD) : {
 # UNMANGLED: .snippy.named.rw 66560 (NOLOAD) : {
-# MANGLED: SNIPPY_Test (rwx) : ORIGIN = 65536, LENGTH = 67072
+# MANGLED: SNIPPY_Test (rwx) : ORIGIN = 65536, LENGTH = 1536
 # MANGLED: .snippy.Test.1.rx 65536: {
 # MANGLED: .snippy.Test.2.rw 66048 (NOLOAD) : {
 # MANGLED: .snippy.Test.named.rw 66560 (NOLOAD) : {

llvm/test/tools/llvm-snippy/linker-script-phdrs.yaml

@@ -31,10 +31,10 @@ histogram:
     - [ADDI, 1.0]
     - [SW, 5.0]
 
-# NODEF: SNIPPY (rwx) : ORIGIN = 65536, LENGTH = 67072
+# NODEF: SNIPPY (rwx) : ORIGIN = 65536, LENGTH = 1536
 # NODEF-NOT: PHDRS
 # NODEF: SECTIONS
-# WITHDEF: SNIPPY (rwx) : ORIGIN = 65536, LENGTH = 67072
+# WITHDEF: SNIPPY (rwx) : ORIGIN = 65536, LENGTH = 1536
 # WITHDEF: PHDRS
 # WITHDEF: SECTIONS
 

llvm/test/tools/llvm-snippy/no-eh-frame.yaml

@@ -0,0 +1,23 @@
+# RUN: llvm-snippy %s -o %t -model-plugin=None
+# RUN: readelf -S %t.elf | not grep eh_frame
+
+options:
+  march: riscv64-unknown-elf
+  mcpu: generic-rv64
+  num-instrs: 100
+
+sections:
+    - no:        1
+      VMA:       0x500000
+      SIZE:      0x100000
+      LMA:       0x500000
+      ACCESS:    rx
+    - no:        2
+      VMA:       0x600000
+      SIZE:      0x100000
+      LMA:       0x600000
+      ACCESS:    rw
+
+histogram:
+    - [ADD, 1.0]
+

llvm/tools/llvm-snippy/include/snippy/Generator/LLVMState.h

@@ -142,6 +142,9 @@ class LLVMState {
     return GV;
   }
 
+  std::unique_ptr<MCStreamer> createObjStreamer(raw_pwrite_stream &OS,
+                                                MCContext &Ctx);
+
   AsmPrinter &getOrCreateAsmPrinter() const;
   MCCodeEmitter &getCodeEmitter() const;
   MCDisassembler &getDisassembler() const;

llvm/tools/llvm-snippy/include/snippy/Target/Target.h

@@ -499,6 +499,10 @@ class SnippyTarget {
   // Registers that should be valid while calling an external function
   virtual std::vector<MCRegister> getGlobalStateRegs() const = 0;
 
+  virtual std::unique_ptr<AsmPrinter>
+  createAsmPrinter(LLVMTargetMachine &TM,
+                   std::unique_ptr<MCStreamer> Streamer) const = 0;
+
 private:
   virtual bool matchesArch(Triple::ArchType Arch) const = 0;
 

llvm/tools/llvm-snippy/lib/FlowGenerator.cpp

@@ -33,6 +33,7 @@
 #include "snippy/Support/Utils.h"
 #include "snippy/Target/Target.h"
 
+#include "llvm/CodeGen/AsmPrinter.h"
 #include "llvm/CodeGen/MachineFunction.h"
 #include "llvm/CodeGen/MachineFunctionPass.h"
 #include "llvm/CodeGen/MachineInstrBuilder.h"
@@ -41,6 +42,7 @@
 #include "llvm/CodeGen/MachineOperand.h"
 #include "llvm/CodeGen/Passes.h"
 #include "llvm/InitializePasses.h"
+#include "llvm/MC/MCStreamer.h"
 #include "llvm/Support/Error.h"
 #include "llvm/Support/raw_ostream.h"
 #include "llvm/Target/TargetLoweringObjectFile.h"
@@ -376,6 +378,7 @@ static RegisterGenerator createRegGen(std::string PluginFileName,
 
 GeneratorResult FlowGenerator::generate(LLVMState &State) {
   auto &LLVMTM = State.getTargetMachine();
+  auto &Tgt = State.getSnippyTarget();
   auto &Ctx = State.getCtx();
   Module M("SnippyModule", Ctx);
 
@@ -462,7 +465,9 @@ GeneratorResult FlowGenerator::generate(LLVMState &State) {
 
   SmallString<32> Output;
   raw_svector_ostream OS(Output);
-  PM.addAsmPrinter(LLVMTM, OS, nullptr, CodeGenFileType::ObjectFile, Context);
+  auto ObjStreamer = State.createObjStreamer(OS, Context);
+  auto AsmPrinter = Tgt.createAsmPrinter(LLVMTM, std::move(ObjStreamer));
+  PM.add(AsmPrinter.release());
 
   PM.run(M);
 

llvm/tools/llvm-snippy/lib/Generator/LLVMState.cpp

@@ -17,6 +17,7 @@
 #include "llvm/MC/MCDisassembler/MCDisassembler.h"
 #include "llvm/MC/MCFixup.h"
 #include "llvm/MC/MCObjectFileInfo.h"
+#include "llvm/MC/MCObjectStreamer.h"
 #include "llvm/MC/MCStreamer.h"
 #include "llvm/MC/TargetRegistry.h"
 #include "llvm/Support/raw_ostream.h"
@@ -107,5 +108,23 @@ bool LLVMState::canAssemble(const MCInst &Inst) const {
   return Tmp.size() > 0;
 }
 
+std::unique_ptr<MCStreamer> LLVMState::createObjStreamer(raw_pwrite_stream &OS,
+                                                         MCContext &MCCtx) {
+  assert(TheTargetMachine);
+  auto MCStreamerOrErr = TheTargetMachine->createMCStreamer(
+      OS, nullptr, CodeGenFileType::ObjectFile, MCCtx);
+  if (auto Err = MCStreamerOrErr.takeError())
+    snippy::fatal(Ctx, "Internal Error creating MCStreamer",
+                  toString(std::move(Err)));
+
+  // We explicitly specified ObjectFile type 3 lines above so we can down-cast
+  // it safely
+  auto *ObjStreamer =
+      static_cast<MCObjectStreamer *>(MCStreamerOrErr->release());
+  ObjStreamer->setEmitEHFrame(false);
+  ObjStreamer->setEmitDebugFrame(false);
+  return std::unique_ptr<MCStreamer>(ObjStreamer);
+}
+
 } // namespace snippy
 } // namespace llvm

llvm/tools/llvm-snippy/lib/Generator/Linker.cpp

@@ -350,16 +350,12 @@ std::vector<std::string> Linker::collectPhdrInfo() const {
 std::string Linker::createLinkerScript(bool Export) const {
   std::string ScriptText;
   llvm::raw_string_ostream STS{ScriptText};
-  // It is needed to fit other object file sections like
-  // .eh_frame
-  constexpr size_t ExtraMemorySpace = 0x10000;
 
   std::string MemoryRegionName =
       MangleName.empty() ? "SNIPPY" : "SNIPPY_" + MangleName;
   STS << "MEMORY {\n"
       << "  " << MemoryRegionName << " (rwx) : ORIGIN = " << MemoryRegion.first
-      << ", LENGTH = "
-      << (MemoryRegion.second - MemoryRegion.first + ExtraMemorySpace) << "\n";
+      << ", LENGTH = " << (MemoryRegion.second - MemoryRegion.first) << "\n";
 
   STS << "}\n";
   auto Phdrs = collectPhdrInfo();
@@ -401,10 +397,6 @@ std::string Linker::createLinkerScript(bool Export) const {
     }
     STS << "\n";
   }
-  STS << "/DISCARD/ :\n"
-      << "{\n"
-      << "  *(.eh_frame)\n"
-      << "}\n";
 
   STS << "}";
   return ScriptText;

llvm/tools/llvm-snippy/lib/Target/RISCV/Target.cpp

@@ -2820,6 +2820,12 @@ class SnippyRISCVTarget final : public SnippyTarget {
   bool canProduceNaN(const MCInstrDesc &InstrDesc) const override {
     return snippy::canProduceNaN(InstrDesc);
   }
+
+  std::unique_ptr<AsmPrinter>
+  createAsmPrinter(LLVMTargetMachine &TM,
+                   std::unique_ptr<MCStreamer> Streamer) const override {
+    return std::make_unique<RISCVAsmPrinter>(TM, std::move(Streamer));
+  }
 };
 
 static unsigned getOpcodeForGPRToFPRInstr(unsigned DstReg, unsigned XLen,

llvm/tools/llvm-snippy/lib/Target/X86/Target.cpp

@@ -491,6 +491,12 @@ class SnippyX86Target : public SnippyTarget {
     reportUnimplementedError();
   }
 
+  std::unique_ptr<AsmPrinter>
+  createAsmPrinter(LLVMTargetMachine &TM,
+                   std::unique_ptr<MCStreamer> Streamer) const override {
+    reportUnimplementedError();
+  }
+
 }; // namespace
 
 bool SnippyX86Target::matchesArch(Triple::ArchType Arch) const {