[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

1 files changed, 16 insertions, 0 deletions

diff --git a/llvm/lib/Target/Mips/Disassembler/MipsDisassembler.cpp b/llvm/lib/Target/Mips/Disassembler/MipsDisassembler.cpp
index 501e066c910..600971986a3 100644
--- a/llvm/lib/Target/Mips/Disassembler/MipsDisassembler.cpp
+++ b/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,