[MC][AsmParser] Hook for post assembly file processing

This patch handles LLVM standalone assembler (llvm-mc) ELF flag setting based on input file
directive processing.

Mips assembly requires processing inline directives that directly and
indirectly affect the output ELF header flags. This patch handles one
".abicalls".

To process these directives we are following the model the code generator
uses by storing state in a container as we go through processing and when
we detect the end of input file processing, AsmParser is notified and we
update the ELF header flags through a MipsELFStreamer method with a call from
MCTargetAsmParser::emitEndOfAsmFile(MCStreamer &OutStreamer).

This patch will allow other targets the same functionality.

Jack


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@191982 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/MC/MCTargetAsmParser.h

@@ -176,6 +176,11 @@ public:
   virtual void convertToMapAndConstraints(unsigned Kind,
                       const SmallVectorImpl<MCParsedAsmOperand*> &Operands) = 0;
 
+  /// End of assembly processing.
+  /// This gets called when all assembly has been read and gives the local
+  /// Target AsmParsers an opportunity for any final data processing, etc..
+  virtual void emitEndOfAsmFile(MCStreamer &Out) {}
+
   virtual const MCExpr *applyModifierToExpr(const MCExpr *E,
                                             MCSymbolRefExpr::VariantKind,
                                             MCContext &Ctx) {

lib/MC/MCParser/AsmParser.cpp

@@ -673,8 +673,10 @@ bool AsmParser::Run(bool NoInitialTextSection, bool NoFinalize) {
 
   // Finalize the output stream if there are no errors and if the client wants
   // us to.
-  if (!HadError && !NoFinalize)
+  if (!HadError && !NoFinalize) {
+    getTargetParser().emitEndOfAsmFile(Out);
     Out.Finish();
+  }
 
   return HadError;
 }
@@ -779,7 +781,8 @@ bool AsmParser::parsePrimaryExpr(const MCExpr *&Res, SMLoc &EndLoc) {
           // temporary label to the streamer and refer to it.
           MCSymbol *Sym = Ctx.CreateTempSymbol();
           Out.EmitLabel(Sym);
-          Res = MCSymbolRefExpr::Create(Sym, MCSymbolRefExpr::VK_None, getContext());
+          Res = MCSymbolRefExpr::Create(Sym, MCSymbolRefExpr::VK_None,
+                                        getContext());
           EndLoc = FirstTokenLoc;
           return false;
         } else

lib/Target/Mips/AsmParser/MipsAsmFlags.h

@@ -0,0 +1,53 @@
+//=== MipsMCAsmFlags.h - MipsMCAsmFlags --------------------------------===//
+//
+//                    The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENCE.TXT for details.
+//
+//===-------------------------------------------------------------------===//
+#ifndef MIPSMCASMFLAGS_H_
+#define MIPSMCASMFLAGS_H_
+
+namespace llvm {
+class MipsMCAsmFlags;
+
+// We have the flags apart from the ELF defines because state will determine
+// the final values put into the ELF flag bits.
+//
+// Currently we have only Relocation Model, but will soon follow with ABI,
+// Architecture, and ASE.
+class MipsMCAsmFlags {
+public:
+  // These act as bit flags because more that one can be
+  // active at the same time, sometimes ;-)
+  enum MAFRelocationModelTy {
+    MAF_RM_DEFAULT = 0,
+    MAF_RM_STATIC = 1,
+    MAF_RM_CPIC = 2,
+    MAF_RM_PIC = 4
+  } MAFRelocationModel;
+
+public:
+  MipsMCAsmFlags() : Model(MAF_RM_DEFAULT) {}
+
+  ~MipsMCAsmFlags() {}
+
+  // Setting a bit we can later translate to the ELF header flags.
+  void setRelocationModel(unsigned RM) { (Model |= RM); }
+
+  bool isModelCpic() const { return (Model & MAF_RM_CPIC) == MAF_RM_CPIC; }
+  bool isModelPic() const { return (Model & MAF_RM_PIC) == MAF_RM_PIC; }
+  bool isModelStatic() const {
+    return (Model & MAF_RM_STATIC) == MAF_RM_STATIC;
+  }
+  bool isModelDefault() const {
+    return (Model & MAF_RM_DEFAULT) == MAF_RM_DEFAULT;
+  }
+
+private:
+  unsigned Model; // pic, cpic, etc.
+};
+}
+
+#endif /* MIPSMCASMFLAGS_H_ */

lib/Target/Mips/AsmParser/MipsAsmParser.cpp

@@ -7,6 +7,8 @@
 //
 //===----------------------------------------------------------------------===//
 
+#include "AsmParser/MipsAsmFlags.h"
+#include "MCTargetDesc/MipsELFStreamer.h"
 #include "MCTargetDesc/MipsMCTargetDesc.h"
 #include "MipsRegisterInfo.h"
 #include "llvm/ADT/StringSwitch.h"
@@ -59,6 +61,7 @@ class MipsAsmParser : public MCTargetAsmParser {
   MCSubtargetInfo &STI;
   MCAsmParser &Parser;
   MipsAssemblerOptions Options;
+  MipsMCAsmFlags Flags;
   bool hasConsumedDollar;
 
 #define GET_ASSEMBLER_HEADER
@@ -228,6 +231,8 @@ class MipsAsmParser : public MCTargetAsmParser {
 
   bool processInstruction(MCInst &Inst, SMLoc IDLoc,
                         SmallVectorImpl<MCInst> &Instructions);
+  void emitEndOfAsmFile(MCStreamer &Out);
+
 public:
   MipsAsmParser(MCSubtargetInfo &sti, MCAsmParser &parser,
                 const MCInstrInfo &MII)
@@ -2172,9 +2177,23 @@ bool MipsAsmParser::ParseDirective(AsmToken DirectiveID) {
     return false;
   }
 
+  if (IDVal == ".abicalls") {
+    Flags.setRelocationModel(MipsMCAsmFlags::MAF_RM_CPIC);
+    if (Parser.getTok().isNot(AsmToken::EndOfStatement))
+      return Error(Parser.getTok().getLoc(), "unexpected token in directive");
+    return false;
+  }
+
   return true;
 }
 
+/// End of assembly processing such as updating ELF header flags.
+void MipsAsmParser::emitEndOfAsmFile(MCStreamer &OutStreamer) {
+  if (MipsELFStreamer *MES = dyn_cast<MipsELFStreamer>(&OutStreamer))
+    MES->emitELFHeaderFlagsAsm(Flags);
+  MCTargetAsmParser::emitEndOfAsmFile(OutStreamer);
+}
+
 extern "C" void LLVMInitializeMipsAsmParser() {
   RegisterMCAsmParser<MipsAsmParser> X(TheMipsTarget);
   RegisterMCAsmParser<MipsAsmParser> Y(TheMipselTarget);

lib/Target/Mips/MCTargetDesc/MipsELFStreamer.cpp

@@ -7,6 +7,7 @@
 //
 //===-------------------------------------------------------------------===//
 #include "MCTargetDesc/MipsELFStreamer.h"
+#include "AsmParser/MipsAsmFlags.h"
 #include "MipsSubtarget.h"
 #include "llvm/MC/MCAssembler.h"
 #include "llvm/MC/MCELF.h"
@@ -66,10 +67,26 @@ namespace llvm {
     Reloc::Model RM = Subtarget.getRelocationModel();
     if (RM == Reloc::PIC_ || RM == Reloc::Default)
       EFlags |= ELF::EF_MIPS_PIC;
-    else if (RM == Reloc::Static)
+
+    MCA.setELFHeaderEFlags(EFlags);
+  }
+
+  // For llvm-mc. Set a group of ELF header flags
+  void MipsELFStreamer::emitELFHeaderFlagsAsm(const MipsMCAsmFlags &Flags) {
+
+    // Update e_header flags
+    MCAssembler &MCA = getAssembler();
+    unsigned EFlags = MCA.getELFHeaderEFlags();
+
+    // Relocation Model
+    if (Flags.isModelCpic() || Flags.isModelDefault())
+      EFlags |= ELF::EF_MIPS_CPIC;
+    if (Flags.isModelStatic())
       ; // Do nothing for Reloc::Static
+    else if (Flags.isModelPic() || Flags.isModelDefault())
+      EFlags |= ELF::EF_MIPS_PIC;
     else
-      llvm_unreachable("Unsupported relocation model for e_flags");
+      assert(0 && "Unsupported relocation model for e_flags");
 
     MCA.setELFHeaderEFlags(EFlags);
   }

lib/Target/Mips/MCTargetDesc/MipsELFStreamer.h

@@ -13,6 +13,7 @@
 
 namespace llvm {
 class MipsAsmPrinter;
+class MipsMCAsmFlags;
 class MipsSubtarget;
 class MCSymbol;
 
@@ -26,6 +27,7 @@ public:
 
   ~MipsELFStreamer() {}
   void emitELFHeaderFlagsCG(const MipsSubtarget &Subtarget);
+  void emitELFHeaderFlagsAsm(const MipsMCAsmFlags &MAFlags);
   void emitMipsSTOCG(const MipsSubtarget &Subtarget,
                      MCSymbol *Sym,
                      unsigned Val);

lib/Target/Mips/MipsAsmPrinter.cpp

@@ -594,8 +594,8 @@ void MipsAsmPrinter::EmitEndOfAsmFile(Module &M) {
   // Emit Mips ELF register info
   Subtarget->getMReginfo().emitMipsReginfoSectionCG(
              OutStreamer, getObjFileLowering(), *Subtarget);
-  if (MipsELFStreamer *MES = dyn_cast<MipsELFStreamer>(&OutStreamer))
-    MES->emitELFHeaderFlagsCG(*Subtarget);
+  MipsELFStreamer *MES = cast<MipsELFStreamer>(&OutStreamer);
+  MES->emitELFHeaderFlagsCG(*Subtarget);
 }
 
 void MipsAsmPrinter::PrintDebugValueComment(const MachineInstr *MI,

test/MC/Mips/mips_directives.s

@@ -1,9 +1,12 @@
 # RUN: llvm-mc -show-encoding -triple mips-unknown-unknown %s | FileCheck %s
+# RUN: llvm-mc -filetype=obj -triple mips-unknown-unknown %s | \
+# RUN: llvm-readobj -h | FileCheck -check-prefix=CHECK-ELF %s
 #
 # CHECK:  .text
 # CHECK:  $BB0_2:
 $BB0_2:
-  .ent directives_test
+    .ent directives_test
+    .abicalls
     .frame    $sp,0,$ra
     .mask     0x00000000,0
     .fmask    0x00000000,0
@@ -43,3 +46,5 @@ $JTI0_0:
 # CHECK:    and     $3, $15, $15       # encoding: [0x01,0xef,0x18,0x24]
     abs.s  f6,FPU_MASK
     and    r3,$t7,STORE_MASK
+
+# CHECK-ELF: Flags [ (0x6)