[PowerPC] ELFv2 MC support for .abiversion directive

ELFv2 binaries are marked by a bit in the ELF header e_flags field.
A new assembler directive .abiversion can be used to set that flag.
This patch implements support in the PowerPC MC streamers to emit the
.abiversion directive (both into assembler and ELF binary output),
as well as support in the assembler parser to parse the .abiversion
directive.

Reviewed by Hal Finkel.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@213484 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Support/ELF.h

@@ -496,6 +496,15 @@ enum {
   R_PPC_REL16_HA              = 252
 };
 
+// Specific e_flags for PPC64
+enum {
+  // e_flags bits specifying ABI:
+  // 1 for original ABI using function descriptors,
+  // 2 for revised ABI without function descriptors,
+  // 0 for unspecified or not using any features affected by the differences.
+  EF_PPC64_ABI = 3
+};
+
 // ELF Relocation types for PPC64
 enum {
   R_PPC64_NONE                = 0,

lib/Target/PowerPC/AsmParser/PPCAsmParser.cpp

@@ -244,6 +244,7 @@ class PPCAsmParser : public MCTargetAsmParser {
   bool ParseDirectiveTC(unsigned Size, SMLoc L);
   bool ParseDirectiveMachine(SMLoc L);
   bool ParseDarwinDirectiveMachine(SMLoc L);
+  bool ParseDirectiveAbiVersion(SMLoc L);
 
   bool MatchAndEmitInstruction(SMLoc IDLoc, unsigned &Opcode,
                                OperandVector &Operands, MCStreamer &Out,
@@ -1412,6 +1413,8 @@ bool PPCAsmParser::ParseDirective(AsmToken DirectiveID) {
       return ParseDirectiveTC(isPPC64()? 8 : 4, DirectiveID.getLoc());
     if (IDVal == ".machine")
       return ParseDirectiveMachine(DirectiveID.getLoc());
+    if (IDVal == ".abiversion")
+      return ParseDirectiveAbiVersion(DirectiveID.getLoc());
   } else {
     if (IDVal == ".machine")
       return ParseDarwinDirectiveMachine(DirectiveID.getLoc());
@@ -1534,6 +1537,27 @@ bool PPCAsmParser::ParseDarwinDirectiveMachine(SMLoc L) {
   return false;
 }
 
+/// ParseDirectiveAbiVersion
+///  ::= .abiversion constant-expression
+bool PPCAsmParser::ParseDirectiveAbiVersion(SMLoc L) {
+  int64_t AbiVersion;
+  if (getParser().parseAbsoluteExpression(AbiVersion)){
+    Error(L, "expected constant expression");
+    return false;
+  }
+  if (getLexer().isNot(AsmToken::EndOfStatement)) {
+    Error(L, "unexpected token in directive");
+    return false;
+  }
+
+  PPCTargetStreamer &TStreamer =
+      *static_cast<PPCTargetStreamer *>(
+           getParser().getStreamer().getTargetStreamer());
+  TStreamer.emitAbiVersion(AbiVersion);
+
+  return false;
+}
+
 /// Force static initialization.
 extern "C" void LLVMInitializePowerPCAsmParser() {
   RegisterMCAsmParser<PPCAsmParser> A(ThePPC32Target);

lib/Target/PowerPC/MCTargetDesc/PPCMCTargetDesc.cpp

@@ -16,12 +16,14 @@
 #include "PPCMCAsmInfo.h"
 #include "PPCTargetStreamer.h"
 #include "llvm/MC/MCCodeGenInfo.h"
+#include "llvm/MC/MCELFStreamer.h"
 #include "llvm/MC/MCInstrInfo.h"
 #include "llvm/MC/MCRegisterInfo.h"
 #include "llvm/MC/MCStreamer.h"
 #include "llvm/MC/MCSubtargetInfo.h"
 #include "llvm/MC/MCSymbol.h"
 #include "llvm/MC/MachineLocation.h"
+#include "llvm/Support/ELF.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/FormattedStream.h"
 #include "llvm/Support/TargetRegistry.h"
@@ -125,12 +127,18 @@ public:
   void emitMachine(StringRef CPU) override {
     OS << "\t.machine " << CPU << '\n';
   }
+  virtual void emitAbiVersion(int AbiVersion) override {
+    OS << "\t.abiversion " << AbiVersion << '\n';
+  }
 };
 
 class PPCTargetELFStreamer : public PPCTargetStreamer {
 public:
   PPCTargetELFStreamer(MCStreamer &S) : PPCTargetStreamer(S) {}
-  void emitTCEntry(const MCSymbol &S) override {
+  MCELFStreamer &getStreamer() {
+    return static_cast<MCELFStreamer &>(Streamer);
+  }
+  virtual void emitTCEntry(const MCSymbol &S) override {
     // Creates a R_PPC64_TOC relocation
     Streamer.EmitSymbolValue(&S, 8);
   }
@@ -138,6 +146,13 @@ public:
     // FIXME: Is there anything to do in here or does this directive only
     // limit the parser?
   }
+  virtual void emitAbiVersion(int AbiVersion) override {
+    MCAssembler &MCA = getStreamer().getAssembler();
+    unsigned Flags = MCA.getELFHeaderEFlags();
+    Flags &= ~ELF::EF_PPC64_ABI;
+    Flags |= (AbiVersion & ELF::EF_PPC64_ABI);
+    MCA.setELFHeaderEFlags(Flags);
+  }
 };
 
 class PPCTargetMachOStreamer : public PPCTargetStreamer {
@@ -150,6 +165,9 @@ public:
     // FIXME: We should update the CPUType, CPUSubType in the Object file if
     // the new values are different from the defaults.
   }
+  virtual void emitAbiVersion(int AbiVersion) override {
+    llvm_unreachable("Unknown pseudo-op: .abiversion");
+  }
 };
 }
 

lib/Target/PowerPC/PPCTargetStreamer.h

@@ -19,6 +19,7 @@ public:
   virtual ~PPCTargetStreamer();
   virtual void emitTCEntry(const MCSymbol &S) = 0;
   virtual void emitMachine(StringRef CPU) = 0;
+  virtual void emitAbiVersion(int AbiVersion) = 0;
 };
 }
 

test/MC/PowerPC/ppc64-abiversion.s

@@ -0,0 +1,9 @@
+
+# RUN: llvm-mc -triple powerpc64-unknown-unknown -filetype=obj %s | \
+# RUN: llvm-readobj -h | FileCheck %s
+# RUN: llvm-mc -triple powerpc64le-unknown-unknown -filetype=obj %s | \
+# RUN: llvm-readobj -h | FileCheck %s
+
+	.abiversion 2
+# CHECK: Flags [ (0x2)
+