MIPS64r6 Relocations R_MIPS_PC21_S2, R_MIPS_PC26_S2

[jkolek]

Summary

Implemented relocations:

• R_MIPS_PC21_S2,
• R_MIPS_PC26_S2.

R_MIPS_PC16 is tested with the new instructions beqc and bnec.

[dsanders]

LGTM with a few nits, particularly the '/ 2' one.

The comment about the A's being in the wrong place seems to be a general problem in our target. I don't think it should block this patch

lib/Target/Mips/MCTargetDesc/MipsAsmBackend.cpp

108

This should either be '>> 2' or '/ 4'

116

Same

lib/Target/Mips/MCTargetDesc/MipsMCCodeEmitter.cpp

263–264

This line break looks strange and isn't necessary.

285–286

Same

test/MC/Mips/mips32r6/reloc-pc16.s

9

It's worth mentioning that the A's are in the wrong place. It's correct for little endian so it looks like they aren't accounting for endianness. I'll take a quick look to see if I can spot the bug

19–20

We should check the address and the value too:

0x0 R_MIPS_PC21_S2 bar 0x0
0x4 R_MIPS_PC21_S2 bar 0x0

test/MC/Mips/mips32r6/reloc-pc21.s

19–20

Same

test/MC/Mips/mips32r6/reloc-pc26.s

19–20

Same

[dsanders]

LGTM

test/MC/Mips/mips32r6/reloc-pc16.s

9

I've found the bug. It affects all targets but I'll have a MIPS specific workaround shortly. Essentially MCFixupKindInfo's bit offset doesn't account for endianness. Big endian targets are using the offset of the top bit of the field, while little endian targets are using the offset of the bottom bit of the field.

[dsanders]

test/MC/Mips/mips32r6/reloc-pc16.s

9

D3889 fixes the bug in llvm-mc. The order we commit in doesn't matter since I'll update the tests in this patch if this is committed first.

[jkolek]

Closed by commit rL209655 (authored by zjovanovic).

include/llvm/Support/ELF.h

enum {
   R_MIPS_TLS_DTPREL_HI16   = 44,
   R_MIPS_TLS_DTPREL_LO16   = 45,
   R_MIPS_TLS_GOTTPREL      = 46,
   R_MIPS_TLS_TPREL32       = 47,
   R_MIPS_TLS_TPREL64       = 48,
   R_MIPS_TLS_TPREL_HI16    = 49,
   R_MIPS_TLS_TPREL_LO16    = 50,
   R_MIPS_GLOB_DAT          = 51,
+  R_MIPS_PC21_S2           = 60,
+  R_MIPS_PC26_S2           = 61,
   R_MIPS16_GOT16           = 102,
   R_MIPS16_HI16            = 104,
   R_MIPS16_LO16            = 105,
   R_MIPS_COPY              = 126,
   R_MIPS_JUMP_SLOT         = 127,
   R_MICROMIPS_26_S1        = 133,
   R_MICROMIPS_HI16         = 134,
   R_MICROMIPS_LO16         = 135,

lib/Object/ELF.cpp

switch (Type) {
       LLVM_ELF_SWITCH_RELOC_TYPE_NAME(R_MIPS_TLS_DTPREL_HI16);
       LLVM_ELF_SWITCH_RELOC_TYPE_NAME(R_MIPS_TLS_DTPREL_LO16);
       LLVM_ELF_SWITCH_RELOC_TYPE_NAME(R_MIPS_TLS_GOTTPREL);
       LLVM_ELF_SWITCH_RELOC_TYPE_NAME(R_MIPS_TLS_TPREL32);
       LLVM_ELF_SWITCH_RELOC_TYPE_NAME(R_MIPS_TLS_TPREL64);
       LLVM_ELF_SWITCH_RELOC_TYPE_NAME(R_MIPS_TLS_TPREL_HI16);
       LLVM_ELF_SWITCH_RELOC_TYPE_NAME(R_MIPS_TLS_TPREL_LO16);
       LLVM_ELF_SWITCH_RELOC_TYPE_NAME(R_MIPS_GLOB_DAT);
+      LLVM_ELF_SWITCH_RELOC_TYPE_NAME(R_MIPS_PC21_S2);
+      LLVM_ELF_SWITCH_RELOC_TYPE_NAME(R_MIPS_PC26_S2);
       LLVM_ELF_SWITCH_RELOC_TYPE_NAME(R_MIPS_COPY);
       LLVM_ELF_SWITCH_RELOC_TYPE_NAME(R_MIPS_JUMP_SLOT);
       LLVM_ELF_SWITCH_RELOC_TYPE_NAME(R_MICROMIPS_26_S1);
       LLVM_ELF_SWITCH_RELOC_TYPE_NAME(R_MICROMIPS_HI16);
       LLVM_ELF_SWITCH_RELOC_TYPE_NAME(R_MICROMIPS_LO16);
       LLVM_ELF_SWITCH_RELOC_TYPE_NAME(R_MICROMIPS_GOT16);
       LLVM_ELF_SWITCH_RELOC_TYPE_NAME(R_MICROMIPS_PC16_S1);
       LLVM_ELF_SWITCH_RELOC_TYPE_NAME(R_MICROMIPS_CALL16);

lib/Target/Mips/MCTargetDesc/MipsAsmBackend.cpp

static unsigned adjustFixupValue(const MCFixup &Fixup, uint64_t Value,
   case Mips::fixup_MICROMIPS_PC16_S1:
     Value -= 4;
     // Forcing a signed division because Value can be negative.
     Value = (int64_t)Value / 2;
     // We now check if Value can be encoded as a 16-bit signed immediate.
     if (!isIntN(16, Value) && Ctx)
       Ctx->FatalError(Fixup.getLoc(), "out of range PC16 fixup");
     break;
+  case Mips::fixup_MIPS_PC21_S2:
+    Value -= 4;
+    // Forcing a signed division because Value can be negative.
+    Value = (int64_t) Value / 4;
+    // We now check if Value can be encoded as a 21-bit signed immediate.
+    if (!isIntN(21, Value) && Ctx)
+      Ctx->FatalError(Fixup.getLoc(), "out of range PC21 fixup");
+    break;
+  case Mips::fixup_MIPS_PC26_S2:
+    Value -= 4;
+    // Forcing a signed division because Value can be negative.
+    Value = (int64_t) Value / 4;
+    // We now check if Value can be encoded as a 26-bit signed immediate.
+    if (!isIntN(26, Value) && Ctx)
+      Ctx->FatalError(Fixup.getLoc(), "out of range PC26 fixup");
+    break;
   }
 
   return Value;
 }
 
 MCObjectWriter *MipsAsmBackend::createObjectWriter(raw_ostream &OS) const {
   return createMipsELFObjectWriter(OS,
     MCELFObjectTargetWriter::getOSABI(OSType), IsLittle, Is64Bit);
const static MCFixupKindInfo Infos[Mips::NumTargetFixupKinds] = {
     { "fixup_Mips_GOT_OFST",     0,     16,   0 },
     { "fixup_Mips_GOT_DISP",     0,     16,   0 },
     { "fixup_Mips_HIGHER",       0,     16,   0 },
     { "fixup_Mips_HIGHEST",      0,     16,   0 },
     { "fixup_Mips_GOT_HI16",     0,     16,   0 },
     { "fixup_Mips_GOT_LO16",     0,     16,   0 },
     { "fixup_Mips_CALL_HI16",    0,     16,   0 },
     { "fixup_Mips_CALL_LO16",    0,     16,   0 },
+    { "fixup_MIPS_PC21_S2",      0,     21,  MCFixupKindInfo::FKF_IsPCRel },
+    { "fixup_MIPS_PC26_S2",      0,     26,  MCFixupKindInfo::FKF_IsPCRel },
     { "fixup_MICROMIPS_26_S1",   0,     26,   0 },
     { "fixup_MICROMIPS_HI16",    0,     16,   0 },
     { "fixup_MICROMIPS_LO16",    0,     16,   0 },
     { "fixup_MICROMIPS_GOT16",   0,     16,   0 },
     { "fixup_MICROMIPS_PC16_S1", 0,     16,   MCFixupKindInfo::FKF_IsPCRel },
     { "fixup_MICROMIPS_CALL16",  0,     16,   0 },
     { "fixup_MICROMIPS_GOT_DISP",        0,     16,   0 },
     { "fixup_MICROMIPS_GOT_PAGE",        0,     16,   0 },

lib/Target/Mips/MCTargetDesc/MipsELFObjectWriter.cpp

case Mips::fixup_MICROMIPS_TLS_DTPREL_LO16:
     Type = ELF::R_MICROMIPS_TLS_DTPREL_LO16;
     break;
   case Mips::fixup_MICROMIPS_TLS_TPREL_HI16:
     Type = ELF::R_MICROMIPS_TLS_TPREL_HI16;
     break;
   case Mips::fixup_MICROMIPS_TLS_TPREL_LO16:
     Type = ELF::R_MICROMIPS_TLS_TPREL_LO16;
     break;
+  case Mips::fixup_MIPS_PC21_S2:
+    Type = ELF::R_MIPS_PC21_S2;
+    break;
+  case Mips::fixup_MIPS_PC26_S2:
+    Type = ELF::R_MIPS_PC26_S2;
+    break;
   }
   return Type;
 }
 
 bool
 MipsELFObjectWriter::needsRelocateWithSymbol(unsigned Type) const {
   // FIXME: This is extremelly conservative. This really needs to use a
   // whitelist with a clear explanation for why each realocation needs to

lib/Target/Mips/MCTargetDesc/MipsFixupKinds.h

enum Fixups {
     fixup_Mips_GOT_LO16,
 
     // resulting in - R_MIPS_CALL_HI16
     fixup_Mips_CALL_HI16,
 
     // resulting in - R_MIPS_CALL_LO16
     fixup_Mips_CALL_LO16,
 
+    // resulting in - R_MIPS_PC21_S2
+    fixup_MIPS_PC21_S2,
+
+    // resulting in - R_MIPS_PC26_S2
+    fixup_MIPS_PC26_S2,
+
     // resulting in - R_MICROMIPS_26_S1
     fixup_MICROMIPS_26_S1,
 
     // resulting in - R_MICROMIPS_HI16
     fixup_MICROMIPS_HI16,
 
     // resulting in - R_MICROMIPS_LO16
     fixup_MICROMIPS_LO16,

lib/Target/Mips/MCTargetDesc/MipsMCCodeEmitter.cpp

getBranchTarget21OpValue(const MCInst &MI, unsigned OpNo,
   const MCOperand &MO = MI.getOperand(OpNo);
 
   // If the destination is an immediate, divide by 4.
   if (MO.isImm()) return MO.getImm() >> 2;
 
   assert(MO.isExpr() &&
          "getBranchTarget21OpValue expects only expressions or immediates");
 
-  // TODO: Push 21 PC fixup.
+  const MCExpr *Expr = MO.getExpr();
+  Fixups.push_back(MCFixup::Create(0, Expr,
+                                   MCFixupKind(Mips::fixup_MIPS_PC21_S2)));
   return 0;
 }
 
 /// getBranchTarget26OpValue - Return binary encoding of the branch
 /// target operand. If the machine operand requires relocation,
 /// record the relocation and return zero.
 unsigned MipsMCCodeEmitter::
 getBranchTarget26OpValue(const MCInst &MI, unsigned OpNo,
                          SmallVectorImpl<MCFixup> &Fixups,
                          const MCSubtargetInfo &STI) const {
 
   const MCOperand &MO = MI.getOperand(OpNo);
 
   // If the destination is an immediate, divide by 4.
   if (MO.isImm()) return MO.getImm() >> 2;
 
   assert(MO.isExpr() &&
          "getBranchTarget26OpValue expects only expressions or immediates");
 
-  // TODO: Push 26 PC fixup.
+  const MCExpr *Expr = MO.getExpr();
+  Fixups.push_back(MCFixup::Create(0, Expr,
+                                   MCFixupKind(Mips::fixup_MIPS_PC26_S2)));
   return 0;
 }
 
 /// getJumpOffset16OpValue - Return binary encoding of the jump
 /// target operand. If the machine operand requires relocation,
 /// record the relocation and return zero.
 unsigned MipsMCCodeEmitter::
 getJumpOffset16OpValue(const MCInst &MI, unsigned OpNo,
                        SmallVectorImpl<MCFixup> &Fixups,

test/MC/Mips/mips32r6/reloc-pc16.s

+# RUN: llvm-mc %s -triple=mips-unknown-linux -show-encoding -mcpu=mips32r6 \
+# RUN:   | FileCheck %s -check-prefix=CHECK-FIXUP
+# RUN: llvm-mc %s -filetype=obj -triple=mips-unknown-linux -mcpu=mips32r6 \
+# RUN:   | llvm-readobj -r | FileCheck %s -check-prefix=CHECK-ELF
+#------------------------------------------------------------------------------
+# Check that the assembler can handle the documented syntax for fixups.
+#------------------------------------------------------------------------------
+# CHECK-FIXUP:   beqc $5, $6, bar # encoding: [0x20'A',0xa6'A',0x00,0x00]
+# CHECK-FIXUP:                    #   fixup A - offset: 0,
+# CHECK-FIXUP:                        value: bar, kind: fixup_Mips_PC16
+# CHECK-FIXUP:   bnec $5, $6, bar # encoding: [0x60'A',0xa6'A',0x00,0x00]
+# CHECK-FIXUP:                    #   fixup A - offset: 0,
+# CHECK-FIXUP:                        value: bar, kind: fixup_Mips_PC16
+#------------------------------------------------------------------------------
+# Check that the appropriate relocations were created.
+#------------------------------------------------------------------------------
+# CHECK-ELF: Relocations [
+# CHECK-ELF:     0x0 R_MIPS_PC16 bar 0x0
+# CHECK-ELF:     0x4 R_MIPS_PC16 bar 0x0
+# CHECK-ELF: ]
+
+  beqc $5, $6, bar
+  bnec $5, $6, bar

test/MC/Mips/mips32r6/reloc-pc21.s

+# RUN: llvm-mc %s -triple=mips-unknown-linux -show-encoding -mcpu=mips32r6 \
+# RUN:   | FileCheck %s -check-prefix=CHECK-FIXUP
+# RUN: llvm-mc %s -filetype=obj -triple=mips-unknown-linux -mcpu=mips32r6 \
+# RUN:   | llvm-readobj -r | FileCheck %s -check-prefix=CHECK-ELF
+#------------------------------------------------------------------------------
+# Check that the assembler can handle the documented syntax for fixups.
+#------------------------------------------------------------------------------
+# CHECK-FIXUP:   beqzc $9, bar # encoding: [0xd9'A',0x20'A',0bAAAAA000,0x00]
+# CHECK-FIXUP:                 #   fixup A - offset: 0,
+# CHECK-FIXUP:                     value: bar, kind: fixup_MIPS_PC21_S2
+# CHECK-FIXUP:   bnezc $9, bar # encoding: [0xf9'A',0x20'A',0bAAAAA000,0x00]
+# CHECK-FIXUP:                 #   fixup A - offset: 0,
+# CHECK-FIXUP:                     value: bar, kind: fixup_MIPS_PC21_S2
+#------------------------------------------------------------------------------
+# Check that the appropriate relocations were created.
+#------------------------------------------------------------------------------
+# CHECK-ELF: Relocations [
+# CHECK-ELF:     0x0 R_MIPS_PC21_S2 bar 0x0
+# CHECK-ELF:     0x4 R_MIPS_PC21_S2 bar 0x0
+# CHECK-ELF: ]
+
+  beqzc $9, bar
+  bnezc $9, bar

test/MC/Mips/mips32r6/reloc-pc26.s

+# RUN: llvm-mc %s -triple=mips-unknown-linux -show-encoding -mcpu=mips32r6 \
+# RUN:   | FileCheck %s -check-prefix=CHECK-FIXUP
+# RUN: llvm-mc %s -filetype=obj -triple=mips-unknown-linux -mcpu=mips32r6 \
+# RUN:   | llvm-readobj -r | FileCheck %s -check-prefix=CHECK-ELF
+#------------------------------------------------------------------------------
+# Check that the assembler can handle the documented syntax for fixups.
+#------------------------------------------------------------------------------
+# CHECK-FIXUP:   balc  bar # encoding: [0xe8'A',A,A,0bAA000000]
+# CHECK-FIXUP:             #   fixup A - offset: 0,
+# CHECK-FIXUP:                 value: bar, kind: fixup_MIPS_PC26_S2
+# CHECK-FIXUP:   bc    bar # encoding: [0xc8'A',A,A,0bAA000000]
+# CHECK-FIXUP:             #   fixup A - offset: 0,
+# CHECK-FIXUP:                 value: bar, kind: fixup_MIPS_PC26_S2
+#------------------------------------------------------------------------------
+# Check that the appropriate relocations were created.
+#------------------------------------------------------------------------------
+# CHECK-ELF: Relocations [
+# CHECK-ELF:     0x0 R_MIPS_PC26_S2 bar 0x0
+# CHECK-ELF:     0x4 R_MIPS_PC26_S2 bar 0x0
+# CHECK-ELF: ]
+
+  balc  bar
+  bc    bar

test/MC/Mips/mips64r6/reloc-pc16.s

+# RUN: llvm-mc %s -triple=mips-unknown-linux -show-encoding -mcpu=mips64r6 \
+# RUN:   | FileCheck %s -check-prefix=CHECK-FIXUP
+# RUN: llvm-mc %s -filetype=obj -triple=mips-unknown-linux -mcpu=mips64r6 \
+# RUN:   | llvm-readobj -r | FileCheck %s -check-prefix=CHECK-ELF
+#------------------------------------------------------------------------------
+# Check that the assembler can handle the documented syntax for fixups.
+#------------------------------------------------------------------------------
+# CHECK-FIXUP:   beqc $5, $6, bar # encoding: [0x20'A',0xa6'A',0x00,0x00]
+# CHECK-FIXUP:                    #   fixup A - offset: 0,
+# CHECK-FIXUP:                        value: bar, kind: fixup_Mips_PC16
+# CHECK-FIXUP:   bnec $5, $6, bar # encoding: [0x60'A',0xa6'A',0x00,0x00]
+# CHECK-FIXUP:                    #   fixup A - offset: 0,
+# CHECK-FIXUP:                        value: bar, kind: fixup_Mips_PC16
+#------------------------------------------------------------------------------
+# Check that the appropriate relocations were created.
+#------------------------------------------------------------------------------
+# CHECK-ELF: Relocations [
+# CHECK-ELF:     0x0 R_MIPS_PC16 bar 0x0
+# CHECK-ELF:     0x4 R_MIPS_PC16 bar 0x0
+# CHECK-ELF: ]
+
+  beqc $5, $6, bar
+  bnec $5, $6, bar

test/MC/Mips/mips64r6/reloc-pc21.s

+# RUN: llvm-mc %s -triple=mips-unknown-linux -show-encoding -mcpu=mips64r6 \
+# RUN:   | FileCheck %s -check-prefix=CHECK-FIXUP
+# RUN: llvm-mc %s -filetype=obj -triple=mips-unknown-linux -mcpu=mips64r6 \
+# RUN:   | llvm-readobj -r | FileCheck %s -check-prefix=CHECK-ELF
+#------------------------------------------------------------------------------
+# Check that the assembler can handle the documented syntax for fixups.
+#------------------------------------------------------------------------------
+# CHECK-FIXUP:   beqzc $9, bar # encoding: [0xd9'A',0x20'A',0bAAAAA000,0x00]
+# CHECK-FIXUP:                 #   fixup A - offset: 0,
+# CHECK-FIXUP:                     value: bar, kind: fixup_MIPS_PC21_S2
+# CHECK-FIXUP:   bnezc $9, bar # encoding: [0xf9'A',0x20'A',0bAAAAA000,0x00]
+# CHECK-FIXUP:                 #   fixup A - offset: 0,
+# CHECK-FIXUP:                     value: bar, kind: fixup_MIPS_PC21_S2
+#------------------------------------------------------------------------------
+# Check that the appropriate relocations were created.
+#------------------------------------------------------------------------------
+# CHECK-ELF: Relocations [
+# CHECK-ELF:     0x0 R_MIPS_PC21_S2 bar 0x0
+# CHECK-ELF:     0x4 R_MIPS_PC21_S2 bar 0x0
+# CHECK-ELF: ]
+
+  beqzc $9, bar
+  bnezc $9, bar

test/MC/Mips/mips64r6/reloc-pc26.s

+# RUN: llvm-mc %s -triple=mips-unknown-linux -show-encoding -mcpu=mips64r6 \
+# RUN:   | FileCheck %s -check-prefix=CHECK-FIXUP
+# RUN: llvm-mc %s -filetype=obj -triple=mips-unknown-linux -mcpu=mips64r6 \
+# RUN:   | llvm-readobj -r | FileCheck %s -check-prefix=CHECK-ELF
+#------------------------------------------------------------------------------
+# Check that the assembler can handle the documented syntax for fixups.
+#------------------------------------------------------------------------------
+# CHECK-FIXUP:   balc  bar # encoding: [0xe8'A',A,A,0bAA000000]
+# CHECK-FIXUP:             #   fixup A - offset: 0,
+# CHECK-FIXUP:                 value: bar, kind: fixup_MIPS_PC26_S2
+# CHECK-FIXUP:   bc    bar # encoding: [0xc8'A',A,A,0bAA000000]
+# CHECK-FIXUP:             #   fixup A - offset: 0,
+# CHECK-FIXUP:                 value: bar, kind: fixup_MIPS_PC26_S2
+#------------------------------------------------------------------------------
+# Check that the appropriate relocations were created.
+#------------------------------------------------------------------------------
+# CHECK-ELF: Relocations [
+# CHECK-ELF:     0x0 R_MIPS_PC26_S2 bar 0x0
+# CHECK-ELF:     0x4 R_MIPS_PC26_S2 bar 0x0
+# CHECK-ELF: ]
+
+  balc  bar
+  bc    bar