[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, 22 insertions, 0 deletions

diff --git a/llvm/lib/Target/Mips/MCTargetDesc/MipsMCCodeEmitter.cpp b/llvm/lib/Target/Mips/MCTargetDesc/MipsMCCodeEmitter.cpp
index 1fe85ec79a5..f561ea8f221 100644
--- a/llvm/lib/Target/Mips/MCTargetDesc/MipsMCCodeEmitter.cpp
+++ b/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.