[mips][microMIPS] MicroMIPS 16-bit unconditional branch instruction B

Implement microMIPS 16-bit unconditional branch instruction B.

Implemented 16-bit microMIPS unconditional instruction has real name B16, and
B is an alias which expands to either B16 or BEQ according to the rules:
b 256 --> b16 256 # R_MICROMIPS_PC10_S1
b 12256 --> beq $zero, $zero, 12256 # R_MICROMIPS_PC16_S1
b label --> beq $zero, $zero, label # R_MICROMIPS_PC16_S1

Differential Revision: http://reviews.llvm.org/D3514

llvm-svn: 226657

llvm/lib/Target/Mips/AsmParser/MipsAsmParser.cpp

@@ -171,6 +171,8 @@ class MipsAsmParser : public MCTargetAsmParser {
 
   bool expandLoadAddressReg(MCInst &Inst, SMLoc IDLoc,
                             SmallVectorImpl<MCInst> &Instructions);
+  bool expandUncondBranchMMPseudo(MCInst &Inst, SMLoc IDLoc,
+                                  SmallVectorImpl<MCInst> &Instructions);
 
   void expandLoadAddressSym(MCInst &Inst, SMLoc IDLoc,
                             SmallVectorImpl<MCInst> &Instructions);
@@ -1422,6 +1424,7 @@ bool MipsAsmParser::needsExpansion(MCInst &Inst) {
   case Mips::LoadAddr32Imm:
   case Mips::LoadAddr32Reg:
   case Mips::LoadImm64Reg:
+  case Mips::B_MM_Pseudo:
     return true;
   default:
     return false;
@@ -1444,6 +1447,8 @@ bool MipsAsmParser::expandInstruction(MCInst &Inst, SMLoc IDLoc,
     return expandLoadAddressImm(Inst, IDLoc, Instructions);
   case Mips::LoadAddr32Reg:
     return expandLoadAddressReg(Inst, IDLoc, Instructions);
+  case Mips::B_MM_Pseudo:
+    return expandUncondBranchMMPseudo(Inst, IDLoc, Instructions);
   }
 }
 
@@ -1729,6 +1734,51 @@ MipsAsmParser::expandLoadAddressSym(MCInst &Inst, SMLoc IDLoc,
   }
 }
 
+bool MipsAsmParser::
+expandUncondBranchMMPseudo(MCInst &Inst, SMLoc IDLoc,
+                           SmallVectorImpl<MCInst> &Instructions) {
+  const MCInstrDesc &MCID = getInstDesc(Inst.getOpcode());
+
+  assert(MCID.getNumOperands() == 1 && "unexpected number of operands");
+
+  MCOperand Offset = Inst.getOperand(0);
+  if (Offset.isExpr()) {
+    Inst.clear();
+    Inst.setOpcode(Mips::BEQ_MM);
+    Inst.addOperand(MCOperand::CreateReg(Mips::ZERO));
+    Inst.addOperand(MCOperand::CreateReg(Mips::ZERO));
+    Inst.addOperand(MCOperand::CreateExpr(Offset.getExpr()));
+  } else {
+    assert(Offset.isImm() && "expected immediate operand kind");
+    if (isIntN(11, Offset.getImm())) {
+      // If offset fits into 11 bits then this instruction becomes microMIPS
+      // 16-bit unconditional branch instruction.
+      Inst.setOpcode(Mips::B16_MM);
+    } else {
+      if (!isIntN(17, Offset.getImm()))
+        Error(IDLoc, "branch target out of range");
+      if (OffsetToAlignment(Offset.getImm(), 1LL << 1))
+        Error(IDLoc, "branch to misaligned address");
+      Inst.clear();
+      Inst.setOpcode(Mips::BEQ_MM);
+      Inst.addOperand(MCOperand::CreateReg(Mips::ZERO));
+      Inst.addOperand(MCOperand::CreateReg(Mips::ZERO));
+      Inst.addOperand(MCOperand::CreateImm(Offset.getImm()));
+    }
+  }
+  Instructions.push_back(Inst);
+
+  if (AssemblerOptions.back()->isReorder()) {
+    // If .set reorder is active, emit a NOP after the branch instruction.
+    MCInst NopInst;
+    NopInst.setOpcode(Mips::MOVE16_MM);
+    NopInst.addOperand(MCOperand::CreateReg(Mips::ZERO));
+    NopInst.addOperand(MCOperand::CreateReg(Mips::ZERO));
+    Instructions.push_back(NopInst);
+  }
+  return false;
+}
+
 void MipsAsmParser::expandMemInst(MCInst &Inst, SMLoc IDLoc,
                                   SmallVectorImpl<MCInst> &Instructions,
                                   bool isLoad, bool isImmOpnd) {

llvm/lib/Target/Mips/Disassembler/MipsDisassembler.cpp

@@ -235,6 +235,13 @@ static DecodeStatus DecodeBranchTarget7MM(MCInst &Inst,
                                           uint64_t Address,
                                           const void *Decoder);
 
+// DecodeBranchTarget10MM - Decode microMIPS branch offset, which is
+// shifted left by 1 bit.
+static DecodeStatus DecodeBranchTarget10MM(MCInst &Inst,
+                                           unsigned Offset,
+                                           uint64_t Address,
+                                           const void *Decoder);
+
 // DecodeBranchTargetMM - Decode microMIPS branch offset, which is
 // shifted left by 1 bit.
 static DecodeStatus DecodeBranchTargetMM(MCInst &Inst,
@@ -1580,6 +1587,15 @@ static DecodeStatus DecodeBranchTarget7MM(MCInst &Inst,
   return MCDisassembler::Success;
 }
 
+static DecodeStatus DecodeBranchTarget10MM(MCInst &Inst,
+                                           unsigned Offset,
+                                           uint64_t Address,
+                                           const void *Decoder) {
+  int32_t BranchOffset = SignExtend32<10>(Offset) << 1;
+  Inst.addOperand(MCOperand::CreateImm(BranchOffset));
+  return MCDisassembler::Success;
+}
+
 static DecodeStatus DecodeBranchTargetMM(MCInst &Inst,
                                          unsigned Offset,
                                          uint64_t Address,

llvm/lib/Target/Mips/InstPrinter/MipsInstPrinter.cpp

@@ -290,6 +290,7 @@ bool MipsInstPrinter::printAlias(const char *Str, const MCInst &MI,
 bool MipsInstPrinter::printAlias(const MCInst &MI, raw_ostream &OS) {
   switch (MI.getOpcode()) {
   case Mips::BEQ:
+  case Mips::BEQ_MM:
     // beq $zero, $zero, $L2 => b $L2
     // beq $r0, $zero, $L2 => beqz $r0, $L2
     return (isReg<Mips::ZERO>(MI, 0) && isReg<Mips::ZERO>(MI, 1) &&

llvm/lib/Target/Mips/MCTargetDesc/MipsAsmBackend.cpp

@@ -111,6 +111,14 @@ static unsigned adjustFixupValue(const MCFixup &Fixup, uint64_t Value,
     if (!isIntN(7, Value) && Ctx)
       Ctx->FatalError(Fixup.getLoc(), "out of range PC7 fixup");
     break;
+  case Mips::fixup_MICROMIPS_PC10_S1:
+    Value -= 2;
+    // Forcing a signed division because Value can be negative.
+    Value = (int64_t) Value / 2;
+    // We now check if Value can be encoded as a 10-bit signed immediate.
+    if (!isIntN(10, Value) && Ctx)
+      Ctx->FatalError(Fixup.getLoc(), "out of range PC10 fixup");
+    break;
   case Mips::fixup_MICROMIPS_PC16_S1:
     Value -= 4;
     // Forcing a signed division because Value can be negative.
@@ -157,7 +165,8 @@ MCObjectWriter *MipsAsmBackend::createObjectWriter(raw_ostream &OS) const {
 //   microMIPS:  x | x | a | b
 
 static bool needsMMLEByteOrder(unsigned Kind) {
-  return Kind >= Mips::fixup_MICROMIPS_26_S1 &&
+  return Kind != Mips::fixup_MICROMIPS_PC10_S1 &&
+         Kind >= Mips::fixup_MICROMIPS_26_S1 &&
          Kind < Mips::LastTargetFixupKind;
 }
 
@@ -190,6 +199,7 @@ void MipsAsmBackend::applyFixup(const MCFixup &Fixup, char *Data,
   switch ((unsigned)Kind) {
   case FK_Data_2:
   case Mips::fixup_Mips_16:
+  case Mips::fixup_MICROMIPS_PC10_S1:
     FullSize = 2;
     break;
   case FK_Data_8:
@@ -280,6 +290,7 @@ getFixupKindInfo(MCFixupKind Kind) const {
     { "fixup_MICROMIPS_LO16",    0,     16,   0 },
     { "fixup_MICROMIPS_GOT16",   0,     16,   0 },
     { "fixup_MICROMIPS_PC7_S1",  0,      7,   MCFixupKindInfo::FKF_IsPCRel },
+    { "fixup_MICROMIPS_PC10_S1", 0,     10,   MCFixupKindInfo::FKF_IsPCRel },
     { "fixup_MICROMIPS_PC16_S1", 0,     16,   MCFixupKindInfo::FKF_IsPCRel },
     { "fixup_MICROMIPS_CALL16",  0,     16,   0 },
     { "fixup_MICROMIPS_GOT_DISP",        0,     16,   0 },
@@ -344,6 +355,7 @@ getFixupKindInfo(MCFixupKind Kind) const {
     { "fixup_MICROMIPS_LO16",   16,     16,   0 },
     { "fixup_MICROMIPS_GOT16",  16,     16,   0 },
     { "fixup_MICROMIPS_PC7_S1",  9,      7,   MCFixupKindInfo::FKF_IsPCRel },
+    { "fixup_MICROMIPS_PC10_S1", 6,     10,   MCFixupKindInfo::FKF_IsPCRel },
     { "fixup_MICROMIPS_PC16_S1",16,     16,   MCFixupKindInfo::FKF_IsPCRel },
     { "fixup_MICROMIPS_CALL16", 16,     16,   0 },
     { "fixup_MICROMIPS_GOT_DISP",        16,     16,   0 },

llvm/lib/Target/Mips/MCTargetDesc/MipsELFObjectWriter.cpp

@@ -165,6 +165,9 @@ unsigned MipsELFObjectWriter::GetRelocType(const MCValue &Target,
   case Mips::fixup_MICROMIPS_PC7_S1:
     Type = ELF::R_MICROMIPS_PC7_S1;
     break;
+  case Mips::fixup_MICROMIPS_PC10_S1:
+    Type = ELF::R_MICROMIPS_PC10_S1;
+    break;
   case Mips::fixup_MICROMIPS_PC16_S1:
     Type = ELF::R_MICROMIPS_PC16_S1;
     break;

llvm/lib/Target/Mips/MCTargetDesc/MipsFixupKinds.h

@@ -161,6 +161,9 @@ namespace Mips {
     // resulting in - R_MICROMIPS_PC7_S1
     fixup_MICROMIPS_PC7_S1,
 
+    // resulting in - R_MICROMIPS_PC10_S1
+    fixup_MICROMIPS_PC10_S1,
+
     // resulting in - R_MICROMIPS_PC16_S1
     fixup_MICROMIPS_PC16_S1,
 

llvm/lib/Target/Mips/MCTargetDesc/MipsMCCodeEmitter.cpp

@@ -242,6 +242,28 @@ getBranchTarget7OpValueMM(const MCInst &MI, unsigned OpNo,
   return 0;
 }
 
+/// getBranchTargetOpValueMMPC10 - Return binary encoding of the microMIPS
+/// 10-bit branch target operand. If the machine operand requires relocation,
+/// record the relocation and return zero.
+unsigned MipsMCCodeEmitter::
+getBranchTargetOpValueMMPC10(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 2.
+  if (MO.isImm()) return MO.getImm() >> 1;
+
+  assert(MO.isExpr() &&
+         "getBranchTargetOpValuePC10 expects only expressions or immediates");
+
+  const MCExpr *Expr = MO.getExpr();
+  Fixups.push_back(MCFixup::Create(0, Expr,
+                   MCFixupKind(Mips::fixup_MICROMIPS_PC10_S1)));
+  return 0;
+}
+
 /// getBranchTargetOpValue - Return binary encoding of the microMIPS branch
 /// target operand. If the machine operand requires relocation,
 /// record the relocation and return zero.

llvm/lib/Target/Mips/MCTargetDesc/MipsMCCodeEmitter.h

@@ -108,6 +108,13 @@ class MipsMCCodeEmitter : public MCCodeEmitter {
                                      SmallVectorImpl<MCFixup> &Fixups,
                                      const MCSubtargetInfo &STI) const;
 
+  // getBranchTargetOpValueMMPC10 - Return binary encoding of the microMIPS
+  // 10-bit branch target operand. If the machine operand requires relocation,
+  // record the relocation and return zero.
+  unsigned getBranchTargetOpValueMMPC10(const MCInst &MI, unsigned OpNo,
+                                        SmallVectorImpl<MCFixup> &Fixups,
+                                        const MCSubtargetInfo &STI) const;
+
   // getBranchTargetOpValue - Return binary encoding of the microMIPS branch
   // target operand. If the machine operand requires relocation,
   // record the relocation and return zero.

llvm/lib/Target/Mips/MicroMipsInstrFormats.td

@@ -238,6 +238,15 @@ class BEQNEZ_FM_MM16<bits<6> op> {
   let Inst{6-0}   = offset;
 }
 
+class B16_FM {
+  bits<10> offset;
+
+  bits<16> Inst;
+
+  let Inst{15-10} = 0x33;
+  let Inst{9-0}   = offset;
+}
+
 //===----------------------------------------------------------------------===//
 // MicroMIPS 32-bit Instruction Formats
 //===----------------------------------------------------------------------===//

llvm/lib/Target/Mips/MicroMipsInstrInfo.td

@@ -135,10 +135,18 @@ def brtarget7_mm : Operand<OtherVT> {
   let ParserMatchClass = MipsJumpTargetAsmOperand;
 }
 
+def brtarget10_mm : Operand<OtherVT> {
+  let EncoderMethod = "getBranchTargetOpValueMMPC10";
+  let OperandType   = "OPERAND_PCREL";
+  let DecoderMethod = "DecodeBranchTarget10MM";
+  let ParserMatchClass = MipsJumpTargetAsmOperand;
+}
+
 def brtarget_mm : Operand<OtherVT> {
   let EncoderMethod = "getBranchTargetOpValueMM";
   let OperandType   = "OPERAND_PCREL";
   let DecoderMethod = "DecodeBranchTargetMM";
+  let ParserMatchClass = MipsJumpTargetAsmOperand;
 }
 
 def simm23_lsl2 : Operand<i32> {
@@ -490,6 +498,18 @@ class LoadMultMM16<string opstr,
   let mayLoad = 1;
 }
 
+class UncondBranchMM16<string opstr> :
+  MicroMipsInst16<(outs), (ins brtarget10_mm:$offset),
+                  !strconcat(opstr, "\t$offset"),
+                  [], IIBranch, FrmI> {
+  let isBranch = 1;
+  let isTerminator = 1;
+  let isBarrier = 1;
+  let hasDelaySlot = 1;
+  let Predicates = [RelocPIC, InMicroMips];
+  let Defs = [AT];
+}
+
 def ADDU16_MM : ArithRMM16<"addu16", GPRMM16Opnd, 1, II_ADDU, add>,
                 ARITH_FM_MM16<0>;
 def SUBU16_MM : ArithRMM16<"subu16", GPRMM16Opnd, 0, II_SUBU, sub>,
@@ -541,6 +561,7 @@ def BEQZ16_MM : CBranchZeroMM<"beqz16", brtarget7_mm, GPRMM16Opnd>,
                 BEQNEZ_FM_MM16<0x23>;
 def BNEZ16_MM : CBranchZeroMM<"bnez16", brtarget7_mm, GPRMM16Opnd>,
                 BEQNEZ_FM_MM16<0x2b>;
+def B16_MM : UncondBranchMM16<"b16">, B16_FM;
 def BREAK16_MM : BrkSdbbp16MM<"break16">, BRKSDBBP16_FM_MM<0x28>;
 def SDBBP16_MM : BrkSdbbp16MM<"sdbbp16">, BRKSDBBP16_FM_MM<0x2C>;
 
@@ -830,6 +851,12 @@ def : MipsPat<(srl GPR32:$src, immZExt5:$imm),
 // MicroMips instruction aliases
 //===----------------------------------------------------------------------===//
 
+class UncondBranchMMPseudo<string opstr> :
+  MipsAsmPseudoInst<(outs), (ins brtarget_mm:$offset),
+                    !strconcat(opstr, "\t$offset")>;
+
+  def B_MM_Pseudo : UncondBranchMMPseudo<"b">;
+
   def : MipsInstAlias<"wait", (WAIT_MM 0x0), 1>;
   def : MipsInstAlias<"nop", (SLL_MM ZERO, ZERO, 0), 1>;
   def : MipsInstAlias<"nop", (MOVE16_MM ZERO, ZERO), 1>;

llvm/lib/Target/Mips/MipsInstrInfo.td

@@ -1582,7 +1582,9 @@ def : MipsInstAlias<"mfc0 $rt, $rd", (MFC0 GPR32Opnd:$rt, GPR32Opnd:$rd, 0), 0>;
 def : MipsInstAlias<"mtc0 $rt, $rd", (MTC0 GPR32Opnd:$rt, GPR32Opnd:$rd, 0), 0>;
 def : MipsInstAlias<"mfc2 $rt, $rd", (MFC2 GPR32Opnd:$rt, GPR32Opnd:$rd, 0), 0>;
 def : MipsInstAlias<"mtc2 $rt, $rd", (MTC2 GPR32Opnd:$rt, GPR32Opnd:$rd, 0), 0>;
+let AdditionalPredicates = [NotInMicroMips] in {
 def : MipsInstAlias<"b $offset", (BEQ ZERO, ZERO, brtarget:$offset), 0>;
+}
 def : MipsInstAlias<"bnez $rs,$offset",
                     (BNE GPR32Opnd:$rs, ZERO, brtarget:$offset), 0>;
 def : MipsInstAlias<"beqz $rs,$offset",

llvm/test/MC/Disassembler/Mips/micromips.txt

@@ -483,3 +483,6 @@
 
 # CHECK: bnez16 $6, 20
 0xaf 0x0a
+
+# CHECK: b16 132
+0xcc 0x42

llvm/test/MC/Disassembler/Mips/micromips_le.txt

@@ -483,3 +483,6 @@
 
 # CHECK: bnez16 $6, 20
 0x0a 0xaf
+
+# CHECK: b16 132
+0x42 0xcc

llvm/test/MC/Mips/micromips-16-bit-instructions.s

@@ -53,6 +53,10 @@
 # CHECK-EL: nop                     # encoding: [0x00,0x00,0x00,0x00]
 # CHECK-EL: bnez16 $6, 20           # encoding: [0x0a,0xaf]
 # CHECK-EL: nop                     # encoding: [0x00,0x00,0x00,0x00]
+# CHECK-EL: b16 132                 # encoding: [0x42,0xcc]
+# CHECK-EL: nop
+# CHECK-EL: b16 132                 # encoding: [0x42,0xcc]
+# CHECK-EL: nop
 # CHECK-EL: break16 8               # encoding: [0x88,0x46]
 # CHECK-EL: sdbbp16 14              # encoding: [0xce,0x46]
 #------------------------------------------------------------------------------
@@ -102,6 +106,10 @@
 # CHECK-EB: nop                     # encoding: [0x00,0x00,0x00,0x00]
 # CHECK-EB: bnez16 $6, 20           # encoding: [0xaf,0x0a]
 # CHECK-EB: nop                     # encoding: [0x00,0x00,0x00,0x00]
+# CHECK-EB: b16 132                 # encoding: [0xcc,0x42]
+# CHECK-EB: nop
+# CHECK-EB: b16 132                 # encoding: [0xcc,0x42]
+# CHECK-EB: nop
 # CHECK-EB: break16 8               # encoding: [0x46,0x88]
 # CHECK-EB: sdbbp16 14              # encoding: [0x46,0xce]
 
@@ -145,5 +153,7 @@
     jr16    $9
     beqz16 $6, 20
     bnez16 $6, 20
+    b   132
+    b16 132
     break16 8
     sdbbp16 14