[mips][microMIPS] Fix issue with offset operand of BALC and BC instructions

Value of offset operand for microMIPS BALC and BC instructions is currently shifted 2 bits, but it should be 1 bit.
Differential Revision: http://reviews.llvm.org/D14770

llvm-svn: 254296

lib/Target/Mips/Disassembler/MipsDisassembler.cpp

@@ -229,6 +229,13 @@ static DecodeStatus DecodeBranchTargetMM(MCInst &Inst,
                                          uint64_t Address,
                                          const void *Decoder);
 
+// DecodeBranchTarget26MM - Decode microMIPS branch offset, which is
+// shifted left by 1 bit.
+static DecodeStatus DecodeBranchTarget26MM(MCInst &Inst,
+                                           unsigned Offset,
+                                           uint64_t Address,
+                                           const void *Decoder);
+
 // DecodeJumpTargetMM - Decode microMIPS jump target, which is
 // shifted left by 1 bit.
 static DecodeStatus DecodeJumpTargetMM(MCInst &Inst,
@@ -1863,6 +1870,16 @@ static DecodeStatus DecodeBranchTargetMM(MCInst &Inst,
   return MCDisassembler::Success;
 }
 
+static DecodeStatus DecodeBranchTarget26MM(MCInst &Inst,
+  unsigned Offset,
+  uint64_t Address,
+  const void *Decoder) {
+  int32_t BranchOffset = SignExtend32<26>(Offset) << 1;
+
+  Inst.addOperand(MCOperand::createImm(BranchOffset));
+  return MCDisassembler::Success;
+}
+
 static DecodeStatus DecodeJumpTargetMM(MCInst &Inst,
                                        unsigned Insn,
                                        uint64_t Address,

lib/Target/Mips/MCTargetDesc/MipsMCCodeEmitter.cpp

@@ -350,6 +350,23 @@ getBranchTarget26OpValue(const MCInst &MI, unsigned OpNo,
   return 0;
 }
 
+/// getBranchTarget26OpValueMM - Return binary encoding of the branch
+/// target operand. If the machine operand requires relocation,
+/// record the relocation and return zero.
+unsigned MipsMCCodeEmitter::getBranchTarget26OpValueMM(
+    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;
+
+  // TODO: Push 26 PC fixup.
+  return 0;
+}
+
 /// getJumpOffset16OpValue - Return binary encoding of the jump
 /// target operand. If the machine operand requires relocation,
 /// record the relocation and return zero.

lib/Target/Mips/MCTargetDesc/MipsMCCodeEmitter.h

@@ -137,6 +137,13 @@ public:
                                     SmallVectorImpl<MCFixup> &Fixups,
                                     const MCSubtargetInfo &STI) const;
 
+  // getBranchTarget26OpValueMM - Return binary encoding of the branch
+  // offset operand. If the machine operand requires relocation,
+  // record the relocation and return zero.
+  unsigned getBranchTarget26OpValueMM(const MCInst &MI, unsigned OpNo,
+                                      SmallVectorImpl<MCFixup> &Fixups,
+                                      const MCSubtargetInfo &STI) const;
+
   // getJumpOffset16OpValue - Return binary encoding of the jump
   // offset operand. If the machine operand requires relocation,
   // record the relocation and return zero.

lib/Target/Mips/MicroMips32r6InstrInfo.td

@@ -11,6 +11,13 @@
 //
 //===----------------------------------------------------------------------===//
 
+def brtarget26_mm : Operand<OtherVT> {
+  let EncoderMethod = "getBranchTarget26OpValueMM";
+  let OperandType = "OPERAND_PCREL";
+  let DecoderMethod = "DecodeBranchTarget26MM";
+  let ParserMatchClass = MipsJumpTargetAsmOperand;
+}
+
 //===----------------------------------------------------------------------===//
 //
 // Instruction Encodings
@@ -238,11 +245,11 @@ class BC_MMR6_DESC_BASE<string instr_asm, DAGOperand opnd>
   bit isBarrier = 1;
 }
 
-class BALC_MMR6_DESC : BC_MMR6_DESC_BASE<"balc", brtarget26> {
+class BALC_MMR6_DESC : BC_MMR6_DESC_BASE<"balc", brtarget26_mm> {
   bit isCall = 1;
   list<Register> Defs = [RA];
 }
-class BC_MMR6_DESC : BC_MMR6_DESC_BASE<"bc", brtarget26>;
+class BC_MMR6_DESC : BC_MMR6_DESC_BASE<"bc", brtarget26_mm>;
 
 class BC16_MMR6_DESC : MicroMipsInst16<(outs), (ins brtarget10_mm:$offset),
                                        !strconcat("bc16", "\t$offset"), [],

test/MC/Disassembler/Mips/micromips32r6/valid.txt

@@ -44,8 +44,8 @@
 0xe0 0x40 0x02 0x9a # CHECK: bgtzalc $2, 1332
 0xe0 0x42 0x02 0x9a # CHECK: bltzalc $2, 1332
 0xc0 0x40 0x02 0x9a # CHECK: blezalc $2, 1332
-0xb4 0x37 0x96 0xb8 # CHECK: balc 14572256
+0xb4 0x37 0x96 0xb8 # CHECK: balc 7286128
-0x94 0x37 0x96 0xb8 # CHECK: bc 14572256
+0x94 0x37 0x96 0xb8 # CHECK: bc 7286128
 0x00 0x44 0x0b 0x3c # CHECK: bitswap $4, $2
 0x00 0x00 0x00 0x07 # CHECK: break
 0x00 0x07 0x00 0x07 # CHECK: break 7

test/MC/Mips/micromips32r6/valid.s

@@ -26,9 +26,9 @@
   bgtzalc $2, 1332         # CHECK: bgtzalc $2, 1332    # encoding: [0xe0,0x40,0x02,0x9a]
   bltzalc $2, 1332         # CHECK: bltzalc $2, 1332    # encoding: [0xe0,0x42,0x02,0x9a]
   blezalc $2, 1332         # CHECK: blezalc $2, 1332    # encoding: [0xc0,0x40,0x02,0x9a]
-  balc 14572256            # CHECK: balc 14572256       # encoding: [0xb4,0x37,0x96,0xb8]
+  balc 7286128             # CHECK: balc 7286128        # encoding: [0xb4,0x37,0x96,0xb8]
   b 132                    # CHECK: bc16 132            # encoding: [0xcc,0x42]
-  bc 14572256              # CHECK: bc 14572256         # encoding: [0x94,0x37,0x96,0xb8]
+  bc 7286128               # CHECK: bc 7286128          # encoding: [0x94,0x37,0x96,0xb8]
   bc16 132                 # CHECK: bc16 132            # encoding: [0xcc,0x42]
   beqzc16 $6, 20           # CHECK: beqzc16 $6, 20      # encoding: [0x8f,0x0a]
   bnezc16 $6, 20           # CHECK: bnezc16 $6, 20      # encoding: [0xaf,0x0a]