[mips][ias] Fix R_MICROMIPS_GOT16 evaluation and eliminate symbol for R_MICROMIPS_(GOT|HI|LO)16

[dsanders]

Summary

The failure r269410 worked around turned out to be caused by an incorrect
evaluation of R_MICROMIPS_GOT16 which then caused the GOT entries to be
incorrect.

This patch fixes the evaluation and reverts r269410.

Depends on D20214 for a fix to '.set micromips'.

[• rafael]

Thanks for tracking it down.

lib/Target/Mips/AsmParser/MipsAsmParser.cpp

bool MipsAsmParser::parseSetFeature(uint64_t Feature) {
   switch (Feature) {
   default:
     llvm_unreachable("Unimplemented feature");
   case Mips::FeatureDSP:
     setFeatureBits(Mips::FeatureDSP, "dsp");
     getTargetStreamer().emitDirectiveSetDsp();
     break;
   case Mips::FeatureMicroMips:
+    setFeatureBits(Mips::FeatureMicroMips, "micromips");
     getTargetStreamer().emitDirectiveSetMicroMips();
     break;
   case Mips::FeatureMips1:
     selectArch("mips1");
     getTargetStreamer().emitDirectiveSetMips1();
     break;
   case Mips::FeatureMips2:
     selectArch("mips2");

lib/Target/Mips/MCTargetDesc/MipsAsmBackend.cpp

static unsigned adjustFixupValue(const MCFixup &Fixup, uint64_t Value,
   case Mips::fixup_Mips_26:
     // So far we are only using this type for jumps.
     // The displacement is then divided by 4 to give us an 28 bit
     // address range.
     Value >>= 2;
     break;
   case Mips::fixup_Mips_HI16:
   case Mips::fixup_Mips_GOT:
+  case Mips::fixup_MICROMIPS_GOT16:
   case Mips::fixup_Mips_GOT_HI16:
   case Mips::fixup_Mips_CALL_HI16:
   case Mips::fixup_MICROMIPS_HI16:
   case Mips::fixup_MIPS_PCHI16:
     // Get the 2nd 16-bits. Also add 1 if bit 15 is 1.
     Value = ((Value + 0x8000) >> 16) & 0xffff;
     break;
   case Mips::fixup_Mips_HIGHER:

lib/Target/Mips/MCTargetDesc/MipsELFObjectWriter.cpp

bool MipsELFObjectWriter::needsRelocateWithSymbol(const MCSymbol &Sym,
   // by the static linker by matching the symbol and offset.
   // We only see one relocation at a time but it's still safe to relocate with
   // the section so long as both relocations make the same decision.
   //
   // Some older linkers may require the symbol for particular cases. Such cases
   // are not supported yet but can be added as required.
   case ELF::R_MIPS_GOT16:
   case ELF::R_MIPS16_GOT16:
+  case ELF::R_MICROMIPS_GOT16:
   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:
     // FIXME: It should be safe to return false for the STO_MIPS_MICROMIPS but
     //        we neglect to handle the adjustment to the LSB of the addend that
     //        it causes in applyFixup() and similar.
     if (cast<MCSymbolELF>(Sym).getOther() & ELF::STO_MIPS_MICROMIPS)
       return true;
     return false;
 
-  // FIXME: These three belong in the previous group but applyFixup() and
-  //        similar do not get the addend correct at the moment.
-  case ELF::R_MICROMIPS_GOT16:
-  case ELF::R_MICROMIPS_HI16:
-  case ELF::R_MICROMIPS_LO16:
-    return true;
-
   case ELF::R_MIPS_16:
   case ELF::R_MIPS_32:
   case ELF::R_MIPS_GPREL32:
     if (cast<MCSymbolELF>(Sym).getOther() & ELF::STO_MIPS_MICROMIPS)
       return true;
     // fallthrough
   case ELF::R_MIPS_26:
   case ELF::R_MIPS_64:

test/MC/Mips/relocation.s

 // RELOC - Check the relocation in the object.
 // FIXUP - Check the fixup on the instruction.
 // ENCBE - Check the big-endian encoding on the instruction.
 // ENCLE - Check the little-endian encoding on the instruction.
 // ????? - Placeholder. Relocation is defined but the way of generating it is
 //         unknown.
 // FIXME - Placeholder. Generation method is known but doesn't work.
 
+// RELOC-LABEL: .rel.text {
 // DATA-LABEL: Name: .text
 // DATA:       SectionData (
 
 // DATA-NEXT:  0000: 00000004 00000000 00000004 0C000000
         .short foo                         // RELOC: R_MIPS_16 foo
 
         .short bar                         // RELOC: R_MIPS_16 .data
 
//      .tpreldword foo                    // FIXME: R_MIPS_TLS_TPREL64 foo
                                            // FIXME: R_MICROMIPS_*
         .long foo-.                        // RELOC: R_MIPS_PC32 foo
 //      .ehword foo                        // FIXME: R_MIPS_EH foo
 
   .data
   .word 0
 bar:
   .word 1
-// DATA-LABEL: Section {
+
+        .section .text_mm, "ax", @progbits
+        .set micromips
+mm:
+// RELOC-LABEL: .rel.text_mm {
+// ENCBE-LABEL: mm:
+// ENCLE-LABEL: mm:
+// DATA-LABEL: Name: .text_mm
+// DATA:       SectionData (
+
+// DATA-NEXT:  0000: 30430000 30420000 30430000 30420004
+        addiu $2, $3, %got(foo_mm)         // RELOC: R_MICROMIPS_GOT16 foo_mm
+                                           // ENCBE: addiu $2, $3, %got(foo_mm) # encoding: [0x30,0x43,A,A]
+                                           // The placement of the 'A' annotations is incorrect. They use 32-bit little endian instead of 2x 16-bit little endian.
+                                           // ENCLE: addiu $2, $3, %got(foo_mm) # encoding: [0x43'A',0x30'A',0x00,0x00]
+                                           // FIXUP: # fixup A - offset: 0, value: %got(foo_mm), kind: fixup_MICROMIPS_GOT16
+        // %got requires a %lo pair
+        addiu $2, $2, %lo(foo_mm)          // RELOC: R_MICROMIPS_LO16 foo_mm
+                                           // ENCBE: addiu $2, $2, %lo(foo_mm) # encoding: [0x30,0x42,A,A]
+                                           // ENCLE: addiu $2, $2, %lo(foo_mm) # encoding: [0x42'A',0x30'A',0x00,0x00]
+                                           // FIXUP: # fixup A - offset: 0, value: %lo(foo_mm), kind: fixup_MICROMIPS_LO16
+
+foo_mm:
+        addiu $2, $3, %got(bar)            // RELOC: R_MICROMIPS_GOT16 .data
+                                           // ENCBE: addiu $2, $3, %got(bar) # encoding: [0x30,0x43,A,A]
+                                           // ENCLE: addiu $2, $3, %got(bar) # encoding: [0x43'A',0x30'A',0x00,0x00]
+                                           // FIXUP: # fixup A - offset: 0, value: %got(bar), kind: fixup_MICROMIPS_GOT16
+        // %got requires a %lo pair
+        addiu $2, $2, %lo(bar)             // RELOC: R_MICROMIPS_LO16 .data
+                                           // ENCBE: addiu $2, $2, %lo(bar) # encoding: [0x30,0x42,A,A]
+                                           // ENCLE: addiu $2, $2, %lo(bar) # encoding: [0x42'A',0x30'A',0x00,0x00]
+                                           // FIXUP: # fixup A - offset: 0, value: %lo(bar), kind: fixup_MICROMIPS_LO16
+
+// DATA-NEXT:  0010: 30430000 30420004 30430001 30420030
+        addiu $2, $3, %got(baz)            // RELOC: R_MICROMIPS_GOT16 .text
+                                           // ENCBE: addiu $2, $3, %got(baz) # encoding: [0x30,0x43,A,A]
+                                           // The placement of the 'A' annotations is incorrect. They use 32-bit little endian instead of 2x 16-bit little endian.
+                                           // ENCLE: addiu $2, $3, %got(baz) # encoding: [0x43'A',0x30'A',0x00,0x00]
+                                           // FIXUP: # fixup A - offset: 0, value: %got(baz), kind: fixup_MICROMIPS_GOT16
+        // %got requires a %lo pair
+        addiu $2, $2, %lo(baz)             // RELOC: R_MICROMIPS_LO16 .text
+                                           // ENCBE: addiu $2, $2, %lo(baz) # encoding: [0x30,0x42,A,A]
+                                           // ENCLE: addiu $2, $2, %lo(baz) # encoding: [0x42'A',0x30'A',0x00,0x00]
+                                           // FIXUP: # fixup A - offset: 0, value: %lo(baz), kind: fixup_MICROMIPS_LO16
+
+        addiu $2, $3, %got(long_mm)        // RELOC: R_MICROMIPS_GOT16 .text
+                                           // ENCBE: addiu $2, $3, %got(long_mm) # encoding: [0x30,0x43,A,A]
+                                           // The placement of the 'A' annotations is incorrect. They use 32-bit little endian instead of 2x 16-bit little endian.
+                                           // ENCLE: addiu $2, $3, %got(long_mm) # encoding: [0x43'A',0x30'A',0x00,0x00]
+                                           // FIXUP: # fixup A - offset: 0, value: %got(long_mm), kind: fixup_MICROMIPS_GOT16
+        // %got requires a %lo pair
+        addiu $2, $2, %lo(long_mm)         // RELOC: R_MICROMIPS_LO16 .text
+                                           // ENCBE: addiu $2, $2, %lo(long_mm) # encoding: [0x30,0x42,A,A]
+                                           // ENCLE: addiu $2, $2, %lo(long_mm) # encoding: [0x42'A',0x30'A',0x00,0x00]
+                                           // FIXUP: # fixup A - offset: 0, value: %lo(long_mm), kind: fixup_MICROMIPS_LO16
+
+// DATA-NEXT:  0020: 30430000 30420000 30430000 30420004
+        addiu $2, $3, %hi(foo_mm)          // RELOC: R_MICROMIPS_HI16 foo_mm
+                                           // ENCBE: addiu $2, $3, %hi(foo_mm) # encoding: [0x30,0x43,A,A]
+                                           // ENCLE: addiu $2, $3, %hi(foo_mm) # encoding: [0x43'A',0x30'A',0x00,0x00]
+                                           // FIXUP: # fixup A - offset: 0, value: %hi(foo_mm), kind: fixup_MICROMIPS_HI16
+
+        addiu $2, $2, %lo(foo_mm)          // RELOC: R_MICROMIPS_LO16 foo_mm
+                                           // ENCBE: addiu $2, $2, %lo(foo_mm) # encoding: [0x30,0x42,A,A]
+                                           // ENCLE: addiu $2, $2, %lo(foo_mm) # encoding: [0x42'A',0x30'A',0x00,0x00]
+                                           // FIXUP: # fixup A - offset: 0, value: %lo(foo_mm), kind: fixup_MICROMIPS_LO16
+
+        addiu $2, $3, %hi(bar)             // RELOC: R_MICROMIPS_HI16 .data
+                                           // ENCBE: addiu $2, $3, %hi(bar) # encoding: [0x30,0x43,A,A]
+                                           // ENCLE: addiu $2, $3, %hi(bar) # encoding: [0x43'A',0x30'A',0x00,0x00]
+                                           // FIXUP: # fixup A - offset: 0, value: %hi(bar), kind: fixup_MICROMIPS_HI16
+
+        addiu $2, $2, %lo(bar)             // RELOC: R_MICROMIPS_LO16 .data
+                                           // ENCBE: addiu $2, $2, %lo(bar) # encoding: [0x30,0x42,A,A]
+                                           // ENCLE: addiu $2, $2, %lo(bar) # encoding: [0x42'A',0x30'A',0x00,0x00]
+                                           // FIXUP: # fixup A - offset: 0, value: %lo(bar), kind: fixup_MICROMIPS_LO16
+
+        .space 65536, 0
+long_mm: