[mips] Add support for '.option pic2'.

The directive '.option pic2' enables PIC from assembly source.
At the moment none of the macros/directives check the PIC bit
but that's going to be fixed relatively soon. For example, the
expansion of macros like 'la' depend on the relocation model.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@204803 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/Mips/AsmParser/MipsAsmParser.cpp

@@ -2596,6 +2596,17 @@ bool MipsAsmParser::parseDirectiveOption() {
     return false;
   }
 
+  if (Option == "pic2") {
+    getTargetStreamer().emitDirectiveOptionPic2();
+    Parser.Lex();
+    if (Parser.getTok().isNot(AsmToken::EndOfStatement)) {
+      Error(Parser.getTok().getLoc(),
+            "unexpected token in .option pic2 directive");
+      Parser.eatToEndOfStatement();
+    }
+    return false;
+  }
+
   // Unknown option.
   Warning(Parser.getTok().getLoc(), "unknown option in .option directive");
   Parser.eatToEndOfStatement();

lib/Target/Mips/MCTargetDesc/MipsTargetStreamer.cpp

@@ -89,6 +89,10 @@ void MipsTargetAsmStreamer::emitDirectiveOptionPic0() {
   OS << "\t.option\tpic0\n";
 }
 
+void MipsTargetAsmStreamer::emitDirectiveOptionPic2() {
+  OS << "\t.option\tpic2\n";
+}
+
 void MipsTargetAsmStreamer::emitFrame(unsigned StackReg, unsigned StackSize,
                                       unsigned ReturnReg) {
   OS << "\t.frame\t$"
@@ -132,6 +136,9 @@ MipsTargetELFStreamer::MipsTargetELFStreamer(MCStreamer &S,
   MCAssembler &MCA = getStreamer().getAssembler();
   uint64_t Features = STI.getFeatureBits();
   Triple T(STI.getTargetTriple());
+  Pic = (MCA.getContext().getObjectFileInfo()->getRelocM() ==  Reloc::PIC_)
+            ? true
+            : false;
 
   // Update e_header flags
   unsigned EFlags = 0;
@@ -311,10 +318,24 @@ void MipsTargetELFStreamer::emitDirectiveAbiCalls() {
 void MipsTargetELFStreamer::emitDirectiveOptionPic0() {
   MCAssembler &MCA = getStreamer().getAssembler();
   unsigned Flags = MCA.getELFHeaderEFlags();
+  // This option overrides other PIC options like -KPIC.
+  Pic = false;
   Flags &= ~ELF::EF_MIPS_PIC;
   MCA.setELFHeaderEFlags(Flags);
 }
 
+void MipsTargetELFStreamer::emitDirectiveOptionPic2() {
+  MCAssembler &MCA = getStreamer().getAssembler();
+  unsigned Flags = MCA.getELFHeaderEFlags();
+  Pic = true;
+  // NOTE: We are following the GAS behaviour here which means the directive
+  // 'pic2' also sets the CPIC bit in the ELF header. This is different from
+  // what is stated in the SYSV ABI which consider the bits EF_MIPS_PIC and
+  // EF_MIPS_CPIC to be mutually exclusive.
+  Flags |= ELF::EF_MIPS_PIC | ELF::EF_MIPS_CPIC;
+  MCA.setELFHeaderEFlags(Flags);
+}
+
 void MipsTargetELFStreamer::emitFrame(unsigned StackReg, unsigned StackSize,
                                       unsigned ReturnReg) {
   // FIXME: implement.

lib/Target/Mips/MipsTargetStreamer.h

@@ -35,6 +35,7 @@ public:
   virtual void emitDirectiveEnt(const MCSymbol &Symbol) = 0;
   virtual void emitDirectiveAbiCalls() = 0;
   virtual void emitDirectiveOptionPic0() = 0;
+  virtual void emitDirectiveOptionPic2() = 0;
   virtual void emitFrame(unsigned StackReg, unsigned StackSize,
                          unsigned ReturnReg) = 0;
   virtual void emitMask(unsigned CPUBitmask, int CPUTopSavedRegOff) = 0;
@@ -66,6 +67,7 @@ public:
   virtual void emitDirectiveEnt(const MCSymbol &Symbol);
   virtual void emitDirectiveAbiCalls();
   virtual void emitDirectiveOptionPic0();
+  virtual void emitDirectiveOptionPic2();
   virtual void emitFrame(unsigned StackReg, unsigned StackSize,
                          unsigned ReturnReg);
   virtual void emitMask(unsigned CPUBitmask, int CPUTopSavedRegOff);
@@ -79,6 +81,7 @@ public:
 class MipsTargetELFStreamer : public MipsTargetStreamer {
   bool MicroMipsEnabled;
   const MCSubtargetInfo &STI;
+  bool Pic;
 
 public:
   bool isMicroMipsEnabled() const { return MicroMipsEnabled; }
@@ -105,6 +108,7 @@ public:
   virtual void emitDirectiveEnt(const MCSymbol &Symbol);
   virtual void emitDirectiveAbiCalls();
   virtual void emitDirectiveOptionPic0();
+  virtual void emitDirectiveOptionPic2();
   virtual void emitFrame(unsigned StackReg, unsigned StackSize,
                          unsigned ReturnReg);
   virtual void emitMask(unsigned CPUBitmask, int CPUTopSavedRegOff);

test/MC/Mips/elf_eflags_pic2.s

@@ -0,0 +1,6 @@
+# RUN: llvm-mc -filetype=obj -triple mipsel-unknown-linux -mcpu=mips32 %s -o -| llvm-readobj -h | FileCheck %s
+
+# This *MUST* match the output of gas compiled with the same triple.
+# CHECK: Flags [ (0x50001006)
+
+.option pic2

test/MC/Mips/mips_directives_bad.s

@@ -46,4 +46,14 @@
     .option pic0 pic2
 # CHECK-NEXT:    :{{[0-9]+}}:{{[0-9]+}}: error: unexpected token in .option pic0 directive
 # CHECK-NEXT:    .option pic0 pic2
+# CHECK-NEXT:                 ^
+
+    .option pic2,
+# CHECK-NEXT:    :{{[0-9]+}}:{{[0-9]+}}: error: unexpected token in .option pic2 directive
+# CHECK-NEXT:    .option pic2,
+# CHECK-NEXT:                ^
+
+    .option pic2 pic3
+# CHECK-NEXT:    :{{[0-9]+}}:{{[0-9]+}}: error: unexpected token in .option pic2 directive
+# CHECK-NEXT:    .option pic2 pic3
 # CHECK-NEXT:                 ^