[mips] Implemented the .hword directive.

[s.egerton]

Summary

In order to pass the tests, this required marking R_MIPS_16 relocations
as needing to point to the symbol and not the section.

[dsanders]

LGTM with the missing zeros and a commit message correction.

... as needing to point to the symbol and not the section.

It's the other way around. needsRelocateWithSymbol() is returning false (it takes the fallthrough path) which means it doesn't need the symbol and can rewrite it in terms of the section base.

lib/Target/Mips/MCTargetDesc/MipsELFObjectWriter.cpp

419

Could you fix this typo while you're there?

test/MC/Mips/mips-data-directives.s

20

There should be more zeros here, it seems to be four bytes short.

lib/Target/Mips/AsmParser/MipsAsmParser.cpp

if (IDVal == ".gpdword") {
     return false;
   }
 
   if (IDVal == ".word") {
     parseDataDirective(4, DirectiveID.getLoc());
     return false;
   }
 
+  if (IDVal == ".hword") {
+    parseDataDirective(2, DirectiveID.getLoc());
+    return false;
+  }
+
   if (IDVal == ".option")
     return parseDirectiveOption();
 
   if (IDVal == ".abicalls") {
     getTargetStreamer().emitDirectiveAbiCalls();
     if (Parser.getTok().isNot(AsmToken::EndOfStatement)) {
       Error(Parser.getTok().getLoc(), 
             "unexpected token, expected end of statement");

lib/Target/Mips/MCTargetDesc/MipsELFObjectWriter.cpp

bool MipsELFObjectWriter::needsRelocateWithSymbol(const MCSymbol &Sym,
   case ELF::R_MIPS_HI16:
   case ELF::R_MIPS16_HI16:
   case ELF::R_MICROMIPS_HI16:
   case ELF::R_MIPS_LO16:
   case ELF::R_MIPS16_LO16:
   case ELF::R_MICROMIPS_LO16:
     return true;
 
+  case ELF::R_MIPS_16:
   case ELF::R_MIPS_32:
     if (cast<MCSymbolELF>(Sym).getOther() & ELF::STO_MIPS_MICROMIPS)
       return true;
     // falltrough
   case ELF::R_MIPS_26:
   case ELF::R_MIPS_64:
   case ELF::R_MIPS_GPREL16:
     return false;
   }
 }
 
 MCObjectWriter *llvm::createMipsELFObjectWriter(raw_pwrite_stream &OS,
                                                 uint8_t OSABI,
                                                 bool IsLittleEndian,
                                                 bool Is64Bit) {
   MCELFObjectTargetWriter *MOTW =
       new MipsELFObjectWriter(Is64Bit, OSABI, Is64Bit, IsLittleEndian);
   return createELFObjectWriter(MOTW, OS, IsLittleEndian);
 }

test/MC/Mips/mips-data-directives.s

 # RUN: llvm-mc %s -arch=mips -mcpu=mips32r2 | \
 # RUN:   FileCheck %s -check-prefix=CHECK-ASM
 #
 # RUN: llvm-mc %s -arch=mips -mcpu=mips32r2 -filetype=obj -o - | \
 # RUN:   llvm-readobj -sections -section-data -section-relocations - | \
 # RUN:     FileCheck %s -check-prefix=CHECK-OBJ
 
 # CHECK-ASM: .4byte 3735929054
 # CHECK-ASM: .8byte -2401050962867405073
+# CHECK-ASM: .2byte 49374
 # CHECK-ASM: .4byte label
 # CHECK-ASM: .8byte label
+# CHECK-ASM: .2byte label
 
 # Checking if the data and reloations were correctly emitted
 # CHECK-OBJ:  Section {
 # CHECK-OBJ:    Name: .data
 # CHECK-OBJ:    SectionData (
-# CHECK-OBJ:      0000: DEADC0DE DEADC0DE DEADBEEF 00000000
+# CHECK-OBJ:      0000: DEADC0DE DEADC0DE DEADBEEF C0DE0000
 # CHECK-OBJ:      0010: 00000000 00000000
 # CHECK-OBJ:    )
 # CHECK-OBJ:  }
 
 # CHECK-OBJ:  Section {
 # CHECK-OBJ:    Name: .rel.data
 # CHECK-OBJ:    Relocations [
-# CHECK-OBJ:      0xC R_MIPS_32 .data 0x0
-# CHECK-OBJ:      0x10 R_MIPS_64 .data 0x0
+# CHECK-OBJ:      0xE R_MIPS_32 .data 0x0
+# CHECK-OBJ:      0x12 R_MIPS_64 .data 0x0
+# CHECK-OBJ:      0x1A R_MIPS_16 .data 0x0
 # CHECK-OBJ:    ]
 # CHECK-OBJ:  }
 
 .data
 label:
         .word 0xdeadc0de
         .dword 0xdeadc0dedeadbeef
+        .hword 0xc0de
 
         .word label
         .dword label
+        .hword label