MIPS: r6 compact branch optimization.

src/mips/assembler-mips.cc

 // Copyright (c) 1994-2006 Sun Microsystems Inc.
 // All Rights Reserved.
 //
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 // - Redistributions of source code must retain the above copyright notice,
 // this list of conditions and the following disclaimer.
 //
@@ skipping 279 matching lines @@
   desc->buffer = buffer_;
   desc->buffer_size = buffer_size_;
   desc->instr_size = pc_offset();
   desc->reloc_size = (buffer_ + buffer_size_) - reloc_info_writer.pos();
   desc->origin = this;
 }
 
 
 void Assembler::Align(int m) {
   DCHECK(m >= 4 && base::bits::IsPowerOfTwo32(m));
+  if (IsPrevInstrCompactBranch()) {
+    nop();
+    ClearCompactBranchState();
+  }
   while ((pc_offset() & (m - 1)) != 0) {
     nop();
   }
 }
 
 
 void Assembler::CodeTargetAlign() {
   // No advantage to aligning branch/call targets to more than
   // single instruction, that I am aware of.
   Align(4);
@@ skipping 136 matching lines @@
 const int kEndOfChain = -4;
 // Determines the end of the Jump chain (a subset of the label link chain).
 const int kEndOfJumpChain = 0;
 
 
 bool Assembler::IsBranch(Instr instr) {
   uint32_t opcode   = GetOpcodeField(instr);
   uint32_t rt_field = GetRtField(instr);
   uint32_t rs_field = GetRsField(instr);
   // Checks if the instruction is a branch.
-  return opcode == BEQ ||
-      opcode == BNE ||
-      opcode == BLEZ ||
-      opcode == BGTZ ||
-      opcode == BEQL ||
-      opcode == BNEL ||
-      opcode == BLEZL ||
-      opcode == BGTZL ||
+  bool isBranch =
+      opcode == BEQ || opcode == BNE || opcode == BLEZ || opcode == BGTZ ||
+      opcode == BEQL || opcode == BNEL || opcode == BLEZL || opcode == BGTZL ||
       (opcode == REGIMM && (rt_field == BLTZ || rt_field == BGEZ ||
                             rt_field == BLTZAL || rt_field == BGEZAL)) ||
       (opcode == COP1 && rs_field == BC1) ||  // Coprocessor branch.
       (opcode == COP1 && rs_field == BC1EQZ) ||
       (opcode == COP1 && rs_field == BC1NEZ);
+  if (!isBranch && IsMipsArchVariant(kMips32r6)) {
+    // All the 3 variants of POP10 (BOVC, BEQC, BEQZALC) and
+    // POP30 (BNVC, BNEC, BNEZALC) are branch ops.
+    isBranch |= opcode == POP10 || opcode == POP30 || opcode == BC ||
+                opcode == BALC ||
+                (opcode == POP66 && rs_field != 0) ||  // BEQZC
+                (opcode == POP76 && rs_field != 0);    // BNEZC
+  }
+  return isBranch;
 }
 
 
+bool Assembler::IsBc(Instr instr) {
+  uint32_t opcode = GetOpcodeField(instr);
+  // Checks if the instruction is a BC or BALC.
+  return opcode == BC || opcode == BALC;
+}
+
+
+bool Assembler::IsBzc(Instr instr) {
+  uint32_t opcode = GetOpcodeField(instr);
+  // Checks if the instruction is BEQZC or BNEZC.
+  return (opcode == POP66 && GetRsField(instr) != 0) ||
+         (opcode == POP76 && GetRsField(instr) != 0);
+}
+
+
 bool Assembler::IsEmittedConstant(Instr instr) {
   uint32_t label_constant = GetLabelConst(instr);
   return label_constant == 0;  // Emitted label const in reg-exp engine.
 }
 
 
 bool Assembler::IsBeq(Instr instr) {
   return GetOpcodeField(instr) == BEQ;
 }
 
 
 bool Assembler::IsBne(Instr instr) {
   return GetOpcodeField(instr) == BNE;
 }
 
 
+bool Assembler::IsBeqzc(Instr instr) {
+  uint32_t opcode = GetOpcodeField(instr);
+  return opcode == POP66 && GetRsField(instr) != 0;
+}
+
+
+bool Assembler::IsBnezc(Instr instr) {
+  uint32_t opcode = GetOpcodeField(instr);
+  return opcode == POP76 && GetRsField(instr) != 0;
+}
+
+
+bool Assembler::IsBeqc(Instr instr) {
+  uint32_t opcode = GetOpcodeField(instr);
+  uint32_t rs = GetRsField(instr);
+  uint32_t rt = GetRtField(instr);
+  return opcode == POP10 && rs != 0 && rs < rt;  // && rt != 0
+}
+
+
+bool Assembler::IsBnec(Instr instr) {
+  uint32_t opcode = GetOpcodeField(instr);
+  uint32_t rs = GetRsField(instr);
+  uint32_t rt = GetRtField(instr);
+  return opcode == POP30 && rs != 0 && rs < rt;  // && rt != 0
+}
+
+
 bool Assembler::IsJump(Instr instr) {
   uint32_t opcode   = GetOpcodeField(instr);
   uint32_t rt_field = GetRtField(instr);
   uint32_t rd_field = GetRdField(instr);
   uint32_t function_field = GetFunctionField(instr);
   // Checks if the instruction is a jump.
   return opcode == J || opcode == JAL ||
       (opcode == SPECIAL && rt_field == 0 &&
       ((function_field == JALR) || (rd_field == 0 && (function_field == JR))));
 }
@@ skipping 65 matching lines @@
 }
 
 
 int32_t Assembler::GetBranchOffset(Instr instr) {
   DCHECK(IsBranch(instr));
   return (static_cast<int16_t>(instr & kImm16Mask)) << 2;
 }
 
 
 bool Assembler::IsLw(Instr instr) {
-  return ((instr & kOpcodeMask) == LW);
+  return (static_cast<uint32_t>(instr & kOpcodeMask) == LW);
 }
 
 
 int16_t Assembler::GetLwOffset(Instr instr) {
   DCHECK(IsLw(instr));
   return ((instr & kImm16Mask));
 }
 
 
 Instr Assembler::SetLwOffset(Instr instr, int16_t offset) {
   DCHECK(IsLw(instr));
 
   // We actually create a new lw instruction based on the original one.
   Instr temp_instr = LW | (instr & kRsFieldMask) | (instr & kRtFieldMask)
       | (offset & kImm16Mask);
 
   return temp_instr;
 }
 
 
 bool Assembler::IsSw(Instr instr) {
-  return ((instr & kOpcodeMask) == SW);
+  return (static_cast<uint32_t>(instr & kOpcodeMask) == SW);
 }
 
 
 Instr Assembler::SetSwOffset(Instr instr, int16_t offset) {
   DCHECK(IsSw(instr));
   return ((instr & ~kImm16Mask) | (offset & kImm16Mask));
 }
 
 
 bool Assembler::IsAddImmediate(Instr instr) {
   return ((instr & kOpcodeMask) == ADDIU);
 }
 
 
 Instr Assembler::SetAddImmediateOffset(Instr instr, int16_t offset) {
   DCHECK(IsAddImmediate(instr));
   return ((instr & ~kImm16Mask) | (offset & kImm16Mask));
 }
 
 
 bool Assembler::IsAndImmediate(Instr instr) {
   return GetOpcodeField(instr) == ANDI;
 }
 
 
+static int32_t OffsetSizeInBits(Instr instr) {
+  if (IsMipsArchVariant(kMips32r6)) {
+    if (Assembler::IsBc(instr)) {
+      return 26;

[ivica.bogosavljevic, 2015/10/15 11:49:08]

Use contstants instead of number

[balazs.kilvady, 2015/10/30 21:11:14]

Done.

+    } else if (Assembler::IsBzc(instr)) {
+      return 21;
+    }
+  }
+  return 16;
+}
+
+
+static inline int32_t AddBranchOffset(int pos, Instr instr) {
+  int32_t bits = OffsetSizeInBits(instr);
+  const int32_t mask = (1 << bits) - 1;
+  bits = 32 - bits;
+
+  // Do NOT change this to <<2. We rely on arithmetic shifts here, assuming
+  // the compiler uses arithmetic shifts for signed integers.
+  int32_t imm = ((instr & mask) << bits) >> (bits - 2);
+
+  if (imm == kEndOfChain) {
+    // EndOfChain sentinel is returned directly, not relative to pc or pos.
+    return kEndOfChain;
+  } else {
+    return pos + Assembler::kBranchPCOffset + imm;
+  }
+}
+
+
 int Assembler::target_at(int pos, bool is_internal) {
   Instr instr = instr_at(pos);
   if (is_internal) {
     if (instr == 0) {
       return kEndOfChain;
     } else {
       int32_t instr_address = reinterpret_cast<int32_t>(buffer_ + pos);
       int delta = static_cast<int>(instr_address - instr);
       DCHECK(pos > delta);
       return pos - delta;
     }
   }
   if ((instr & ~kImm16Mask) == 0) {
     // Emitted label constant, not part of a branch.
     if (instr == 0) {
        return kEndOfChain;
      } else {
        int32_t imm18 =((instr & static_cast<int32_t>(kImm16Mask)) << 16) >> 14;
        return (imm18 + pos);
      }
   }
   // Check we have a branch or jump instruction.
   DCHECK(IsBranch(instr) || IsLui(instr));
-  // Do NOT change this to <<2. We rely on arithmetic shifts here, assuming
-  // the compiler uses arithmetic shifts for signed integers.
   if (IsBranch(instr)) {
-    int32_t imm18 = ((instr & static_cast<int32_t>(kImm16Mask)) << 16) >> 14;
-
-    if (imm18 == kEndOfChain) {
-      // EndOfChain sentinel is returned directly, not relative to pc or pos.
-      return kEndOfChain;
-    } else {
-      return pos + kBranchPCOffset + imm18;
-    }
-  } else if (IsLui(instr)) {
+    return AddBranchOffset(pos, instr);
+  } else {
     Instr instr_lui = instr_at(pos + 0 * Assembler::kInstrSize);
     Instr instr_ori = instr_at(pos + 1 * Assembler::kInstrSize);
     DCHECK(IsOri(instr_ori));

[ivica.bogosavljevic, 2015/10/15 11:49:08]

Since isLui is not part of else if, then we should DCHECK(IsLui(instr_lui));
here

[balazs.kilvady, 2015/10/30 21:11:14]

That check is covered at line 724

     int32_t imm = (instr_lui & static_cast<int32_t>(kImm16Mask)) << kLuiShift;
     imm |= (instr_ori & static_cast<int32_t>(kImm16Mask));
 
     if (imm == kEndOfJumpChain) {
       // EndOfChain sentinel is returned directly, not relative to pc or pos.
       return kEndOfChain;
     } else {
       uint32_t instr_address = reinterpret_cast<int32_t>(buffer_ + pos);
       int32_t delta = instr_address - imm;
       DCHECK(pos > delta);
       return pos - delta;
     }
-  } else {
-    UNREACHABLE();
-    return 0;
   }
+  return 0;
 }
 
 
+static inline Instr SetBranchOffset(int32_t pos, int32_t target_pos,
+                                    Instr instr) {
+  int32_t bits = OffsetSizeInBits(instr);
+  int32_t imm = target_pos - (pos + Assembler::kBranchPCOffset);
+  DCHECK((imm & 3) == 0);
+  imm >>= 2;
+
+  const int32_t mask = (1 << bits) - 1;
+  instr &= ~mask;
+  DCHECK(is_intn(imm, bits));
+
+  return instr | (imm & mask);
+}
+
+
 void Assembler::target_at_put(int32_t pos, int32_t target_pos,
                               bool is_internal) {
   Instr instr = instr_at(pos);
 
   if (is_internal) {
     uint32_t imm = reinterpret_cast<uint32_t>(buffer_) + target_pos;
     instr_at_put(pos, imm);
     return;
   }
   if ((instr & ~kImm16Mask) == 0) {
     DCHECK(target_pos == kEndOfChain || target_pos >= 0);
     // Emitted label constant, not part of a branch.
     // Make label relative to Code* of generated Code object.
     instr_at_put(pos, target_pos + (Code::kHeaderSize - kHeapObjectTag));
     return;
   }
 
   DCHECK(IsBranch(instr) || IsLui(instr));
   if (IsBranch(instr)) {
-    int32_t imm18 = target_pos - (pos + kBranchPCOffset);
-    DCHECK((imm18 & 3) == 0);
-
-    instr &= ~kImm16Mask;
-    int32_t imm16 = imm18 >> 2;
-    DCHECK(is_int16(imm16));
-
-    instr_at_put(pos, instr | (imm16 & kImm16Mask));
-  } else if (IsLui(instr)) {
+    instr = SetBranchOffset(pos, target_pos, instr);
+    instr_at_put(pos, instr);
+  } else {
     Instr instr_lui = instr_at(pos + 0 * Assembler::kInstrSize);
     Instr instr_ori = instr_at(pos + 1 * Assembler::kInstrSize);
     DCHECK(IsOri(instr_ori));

[ivica.bogosavljevic, 2015/10/15 11:49:08]

Since isLui is not part of else if, then we should DCHECK(IsLui(instr_lui));here

[balazs.kilvady, 2015/10/30 21:11:14]

Check covered at line 780

     uint32_t imm = reinterpret_cast<uint32_t>(buffer_) + target_pos;
     DCHECK((imm & 3) == 0);
 
     instr_lui &= ~kImm16Mask;
     instr_ori &= ~kImm16Mask;
 
     instr_at_put(pos + 0 * Assembler::kInstrSize,
                  instr_lui | ((imm & kHiMask) >> kLuiShift));
     instr_at_put(pos + 1 * Assembler::kInstrSize,
                  instr_ori | (imm & kImm16Mask));
-  } else {
-    UNREACHABLE();
   }
 }
 
 
 void Assembler::print(Label* L) {
   if (L->is_unused()) {
     PrintF("unused label\n");
   } else if (L->is_bound()) {
     PrintF("bound label to %d\n", L->pos());
   } else if (L->is_linked()) {
@@ skipping 28 matching lines @@
   while (L->is_linked()) {
     int32_t fixup_pos = L->pos();
     int32_t dist = pos - fixup_pos;
     is_internal = internal_reference_positions_.find(fixup_pos) !=
                   internal_reference_positions_.end();
     next(L, is_internal);  // Call next before overwriting link with target at
                            // fixup_pos.
     Instr instr = instr_at(fixup_pos);
     if (is_internal) {
       target_at_put(fixup_pos, pos, is_internal);
-    } else if (!is_internal && IsBranch(instr)) {
-      if (dist > kMaxBranchOffset) {
-        if (trampoline_pos == kInvalidSlotPos) {
-          trampoline_pos = get_trampoline_entry(fixup_pos);
-          CHECK(trampoline_pos != kInvalidSlotPos);
+    } else {
+      if (IsBranch(instr)) {
+        if (dist > kMaxBranchOffset) {
+          if (trampoline_pos == kInvalidSlotPos) {
+            trampoline_pos = get_trampoline_entry(fixup_pos);
+            CHECK(trampoline_pos != kInvalidSlotPos);
+          }
+          CHECK((trampoline_pos - fixup_pos) <= kMaxBranchOffset);
+          target_at_put(fixup_pos, trampoline_pos, false);
+          fixup_pos = trampoline_pos;
+          dist = pos - fixup_pos;
         }
-        CHECK((trampoline_pos - fixup_pos) <= kMaxBranchOffset);
-        target_at_put(fixup_pos, trampoline_pos, false);
-        fixup_pos = trampoline_pos;
-        dist = pos - fixup_pos;
+        target_at_put(fixup_pos, pos, false);
+      } else {
+        target_at_put(fixup_pos, pos, false);
       }
-      target_at_put(fixup_pos, pos, false);
-    } else {
-      target_at_put(fixup_pos, pos, false);
     }
   }
   L->bind_to(pos);
 
   // Keep track of the last bound label so we don't eliminate any instructions
   // before a bound label.
   if (pos > last_bound_pos_)
     last_bound_pos_ = pos;
 }
 
@@ skipping 199 matching lines @@
     }
   }
 
   uint32_t imm = reinterpret_cast<uint32_t>(buffer_) + target_pos;
   DCHECK((imm & 3) == 0);
 
   return imm;
 }
 
 
-int32_t Assembler::branch_offset(Label* L, bool jump_elimination_allowed) {
+int32_t Assembler::branch_offset_helper(Label* L, bool jump_elimination_allowed,

[ivica.bogosavljevic, 2015/10/15 11:49:08]

Bravo for removing all these functions!

+                                        int bits) {
   int32_t target_pos;
+  int32_t pad = IsPrevInstrCompactBranch() ? kInstrSize : 0;
 
   if (L->is_bound()) {
     target_pos = L->pos();
   } else {
     if (L->is_linked()) {
       target_pos = L->pos();
-      L->link_to(pc_offset());
+      L->link_to(pc_offset() + pad);
     } else {
-      L->link_to(pc_offset());
+      L->link_to(pc_offset() + pad);
       if (!trampoline_emitted_) {
         unbound_labels_count_++;
         next_buffer_check_ -= kTrampolineSlotsSize;
-      }
-      return kEndOfChain;
-    }
-  }
-
-  int32_t offset = target_pos - (pc_offset() + kBranchPCOffset);
-  DCHECK((offset & 3) == 0);
-  DCHECK(is_int16(offset >> 2));
-
-  return offset;
-}
-
-
-int32_t Assembler::branch_offset_compact(Label* L,
-    bool jump_elimination_allowed) {
-  int32_t target_pos;
-  if (L->is_bound()) {
-    target_pos = L->pos();
-  } else {
-    if (L->is_linked()) {
-      target_pos = L->pos();
-      L->link_to(pc_offset());
-    } else {
-      L->link_to(pc_offset());
-      if (!trampoline_emitted_) {
-        unbound_labels_count_++;
-        next_buffer_check_ -= kTrampolineSlotsSize;
-      }
-      return kEndOfChain;
-    }
-  }
-
-  int32_t offset = target_pos - pc_offset();
-  DCHECK((offset & 3) == 0);
-  DCHECK(is_int16(offset >> 2));
-
-  return offset;
-}
-
-
-int32_t Assembler::branch_offset21(Label* L, bool jump_elimination_allowed) {
-  int32_t target_pos;
-
-  if (L->is_bound()) {
-    target_pos = L->pos();
-  } else {
-    if (L->is_linked()) {
-      target_pos = L->pos();
-      L->link_to(pc_offset());
-    } else {
-      L->link_to(pc_offset());
-      if (!trampoline_emitted_) {
-        unbound_labels_count_++;
-        next_buffer_check_ -= kTrampolineSlotsSize;
       }
       return kEndOfChain;
     }
   }
 
-  int32_t offset = target_pos - (pc_offset() + kBranchPCOffset);
+  int32_t offset = target_pos - (pc_offset() + kBranchPCOffset + pad);
+  DCHECK(is_intn(offset, bits + 2));
   DCHECK((offset & 3) == 0);
-  DCHECK(((offset >> 2) & 0xFFE00000) == 0);  // Offset is 21bit width.
 
   return offset;
 }
-
-
-int32_t Assembler::branch_offset21_compact(Label* L,
-    bool jump_elimination_allowed) {
-  int32_t target_pos;
-
-  if (L->is_bound()) {
-    target_pos = L->pos();
-  } else {
-    if (L->is_linked()) {
-      target_pos = L->pos();
-      L->link_to(pc_offset());
-    } else {
-      L->link_to(pc_offset());
-      if (!trampoline_emitted_) {
-        unbound_labels_count_++;
-        next_buffer_check_ -= kTrampolineSlotsSize;
-      }
-      return kEndOfChain;
-    }
-  }
-
-  int32_t offset = target_pos - pc_offset();
-  DCHECK((offset & 3) == 0);
-  DCHECK(((offset >> 2) & 0xFFe00000) == 0);  // Offset is 21bit width.
-
-  return offset;
-}
 
 
 void Assembler::label_at_put(Label* L, int at_offset) {
   int target_pos;
   if (L->is_bound()) {
     target_pos = L->pos();
     instr_at_put(at_offset, target_pos + (Code::kHeaderSize - kHeapObjectTag));
   } else {
     if (L->is_linked()) {
       target_pos = L->pos();  // L's link.
@@ skipping 16 matching lines @@
 
 
 //------- Branch and jump instructions --------
 
 void Assembler::b(int16_t offset) {
   beq(zero_reg, zero_reg, offset);
 }
 
 
 void Assembler::bal(int16_t offset) {
-  positions_recorder()->WriteRecordedPositions();
   bgezal(zero_reg, offset);
 }
 
 
 void Assembler::bc(int32_t offset) {
   DCHECK(IsMipsArchVariant(kMips32r6));
   GenInstrImmediate(BC, offset);
+  EmittedCompactBranchInstruction();
 }
 
 
 void Assembler::balc(int32_t offset) {
   DCHECK(IsMipsArchVariant(kMips32r6));
-  positions_recorder()->WriteRecordedPositions();
   GenInstrImmediate(BALC, offset);
+  EmittedCompactBranchInstruction();
 }
 
 
 void Assembler::beq(Register rs, Register rt, int16_t offset) {
   BlockTrampolinePoolScope block_trampoline_pool(this);
   GenInstrImmediate(BEQ, rs, rt, offset);
   BlockTrampolinePoolFor(1);  // For associated delay slot.
 }
 
 
 void Assembler::bgez(Register rs, int16_t offset) {
   BlockTrampolinePoolScope block_trampoline_pool(this);
   GenInstrImmediate(REGIMM, rs, BGEZ, offset);
   BlockTrampolinePoolFor(1);  // For associated delay slot.
 }
 
 
 void Assembler::bgezc(Register rt, int16_t offset) {
   DCHECK(IsMipsArchVariant(kMips32r6));
   DCHECK(!(rt.is(zero_reg)));
   GenInstrImmediate(BLEZL, rt, rt, offset);
+  EmittedCompactBranchInstruction();
 }
 
 
 void Assembler::bgeuc(Register rs, Register rt, int16_t offset) {
   DCHECK(IsMipsArchVariant(kMips32r6));
   DCHECK(!(rs.is(zero_reg)));
   DCHECK(!(rt.is(zero_reg)));
   DCHECK(rs.code() != rt.code());
   GenInstrImmediate(BLEZ, rs, rt, offset);
+  EmittedCompactBranchInstruction();
 }
 
 
 void Assembler::bgec(Register rs, Register rt, int16_t offset) {
   DCHECK(IsMipsArchVariant(kMips32r6));
   DCHECK(!(rs.is(zero_reg)));
   DCHECK(!(rt.is(zero_reg)));
   DCHECK(rs.code() != rt.code());
   GenInstrImmediate(BLEZL, rs, rt, offset);
+  EmittedCompactBranchInstruction();
 }
 
 
 void Assembler::bgezal(Register rs, int16_t offset) {
   DCHECK(!IsMipsArchVariant(kMips32r6) || rs.is(zero_reg));
   BlockTrampolinePoolScope block_trampoline_pool(this);
-  positions_recorder()->WriteRecordedPositions();
   GenInstrImmediate(REGIMM, rs, BGEZAL, offset);
   BlockTrampolinePoolFor(1);  // For associated delay slot.
 }
 
 
 void Assembler::bgtz(Register rs, int16_t offset) {
   BlockTrampolinePoolScope block_trampoline_pool(this);
   GenInstrImmediate(BGTZ, rs, zero_reg, offset);
   BlockTrampolinePoolFor(1);  // For associated delay slot.
 }
 
 
 void Assembler::bgtzc(Register rt, int16_t offset) {
   DCHECK(IsMipsArchVariant(kMips32r6));
   DCHECK(!(rt.is(zero_reg)));
   GenInstrImmediate(BGTZL, zero_reg, rt, offset);
+  EmittedCompactBranchInstruction();
 }
 
 
 void Assembler::blez(Register rs, int16_t offset) {
   BlockTrampolinePoolScope block_trampoline_pool(this);
   GenInstrImmediate(BLEZ, rs, zero_reg, offset);
   BlockTrampolinePoolFor(1);  // For associated delay slot.
 }
 
 
 void Assembler::blezc(Register rt, int16_t offset) {
   DCHECK(IsMipsArchVariant(kMips32r6));
   DCHECK(!(rt.is(zero_reg)));
   GenInstrImmediate(BLEZL, zero_reg, rt, offset);
+  EmittedCompactBranchInstruction();
 }
 
 
 void Assembler::bltzc(Register rt, int16_t offset) {
   DCHECK(IsMipsArchVariant(kMips32r6));
-  DCHECK(!(rt.is(zero_reg)));
+  DCHECK(!rt.is(zero_reg));
   GenInstrImmediate(BGTZL, rt, rt, offset);
+  EmittedCompactBranchInstruction();
 }
 
 
 void Assembler::bltuc(Register rs, Register rt, int16_t offset) {
   DCHECK(IsMipsArchVariant(kMips32r6));
   DCHECK(!(rs.is(zero_reg)));
   DCHECK(!(rt.is(zero_reg)));
   DCHECK(rs.code() != rt.code());
   GenInstrImmediate(BGTZ, rs, rt, offset);
+  EmittedCompactBranchInstruction();
 }
 
 
 void Assembler::bltc(Register rs, Register rt, int16_t offset) {
   DCHECK(IsMipsArchVariant(kMips32r6));
-  DCHECK(!(rs.is(zero_reg)));
-  DCHECK(!(rt.is(zero_reg)));
+  DCHECK(!rs.is(zero_reg));
+  DCHECK(!rt.is(zero_reg));
   DCHECK(rs.code() != rt.code());
   GenInstrImmediate(BGTZL, rs, rt, offset);
+  EmittedCompactBranchInstruction();
 }
 
 
 void Assembler::bltz(Register rs, int16_t offset) {
   BlockTrampolinePoolScope block_trampoline_pool(this);
   GenInstrImmediate(REGIMM, rs, BLTZ, offset);
   BlockTrampolinePoolFor(1);  // For associated delay slot.
 }
 
 
 void Assembler::bltzal(Register rs, int16_t offset) {
   DCHECK(!IsMipsArchVariant(kMips32r6) || rs.is(zero_reg));
   BlockTrampolinePoolScope block_trampoline_pool(this);
-  positions_recorder()->WriteRecordedPositions();
   GenInstrImmediate(REGIMM, rs, BLTZAL, offset);
   BlockTrampolinePoolFor(1);  // For associated delay slot.
 }
 
 
 void Assembler::bne(Register rs, Register rt, int16_t offset) {
   BlockTrampolinePoolScope block_trampoline_pool(this);
   GenInstrImmediate(BNE, rs, rt, offset);
   BlockTrampolinePoolFor(1);  // For associated delay slot.
 }
 
 
 void Assembler::bovc(Register rs, Register rt, int16_t offset) {
   DCHECK(IsMipsArchVariant(kMips32r6));
   DCHECK(!(rs.is(zero_reg)));
   DCHECK(rs.code() >= rt.code());
   GenInstrImmediate(ADDI, rs, rt, offset);
+  EmittedCompactBranchInstruction();
 }
 
 
 void Assembler::bnvc(Register rs, Register rt, int16_t offset) {
   DCHECK(IsMipsArchVariant(kMips32r6));
   DCHECK(!(rs.is(zero_reg)));
   DCHECK(rs.code() >= rt.code());
   GenInstrImmediate(DADDI, rs, rt, offset);
+  EmittedCompactBranchInstruction();
 }
 
 
 void Assembler::blezalc(Register rt, int16_t offset) {
   DCHECK(IsMipsArchVariant(kMips32r6));
   DCHECK(!(rt.is(zero_reg)));
   GenInstrImmediate(BLEZ, zero_reg, rt, offset);
+  EmittedCompactBranchInstruction();
 }
 
 
 void Assembler::bgezalc(Register rt, int16_t offset) {
   DCHECK(IsMipsArchVariant(kMips32r6));
   DCHECK(!(rt.is(zero_reg)));
   GenInstrImmediate(BLEZ, rt, rt, offset);
+  EmittedCompactBranchInstruction();
 }
 
 
 void Assembler::bgezall(Register rs, int16_t offset) {
   DCHECK(IsMipsArchVariant(kMips32r6));
   DCHECK(!(rs.is(zero_reg)));
   GenInstrImmediate(REGIMM, rs, BGEZALL, offset);
 }
 
 
 void Assembler::bltzalc(Register rt, int16_t offset) {
   DCHECK(IsMipsArchVariant(kMips32r6));
   DCHECK(!(rt.is(zero_reg)));
   GenInstrImmediate(BGTZ, rt, rt, offset);
+  EmittedCompactBranchInstruction();
 }
 
 
 void Assembler::bgtzalc(Register rt, int16_t offset) {
   DCHECK(IsMipsArchVariant(kMips32r6));
   DCHECK(!(rt.is(zero_reg)));
   GenInstrImmediate(BGTZ, zero_reg, rt, offset);
+  EmittedCompactBranchInstruction();
 }
 
 
 void Assembler::beqzalc(Register rt, int16_t offset) {
   DCHECK(IsMipsArchVariant(kMips32r6));
   DCHECK(!(rt.is(zero_reg)));
   GenInstrImmediate(ADDI, zero_reg, rt, offset);
+  EmittedCompactBranchInstruction();
 }
 
 
 void Assembler::bnezalc(Register rt, int16_t offset) {
   DCHECK(IsMipsArchVariant(kMips32r6));
   DCHECK(!(rt.is(zero_reg)));
   GenInstrImmediate(DADDI, zero_reg, rt, offset);
+  EmittedCompactBranchInstruction();
 }
 
 
 void Assembler::beqc(Register rs, Register rt, int16_t offset) {
   DCHECK(IsMipsArchVariant(kMips32r6));
-  DCHECK(rs.code() < rt.code());
-  GenInstrImmediate(ADDI, rs, rt, offset);
+  DCHECK(rs.code() != rt.code() && rs.code() != 0 && rt.code() != 0);
+  if (rs.code() < rt.code()) {
+    GenInstrImmediate(ADDI, rs, rt, offset);
+  } else {
+    GenInstrImmediate(ADDI, rt, rs, offset);
+  }
+  EmittedCompactBranchInstruction();
 }
 
 
 void Assembler::beqzc(Register rs, int32_t offset) {
   DCHECK(IsMipsArchVariant(kMips32r6));
   DCHECK(!(rs.is(zero_reg)));
   Instr instr = POP66 | (rs.code() << kRsShift) | (offset & kImm21Mask);
   emit(instr);
+  EmittedCompactBranchInstruction();
 }
 
 
 void Assembler::bnec(Register rs, Register rt, int16_t offset) {
   DCHECK(IsMipsArchVariant(kMips32r6));
-  DCHECK(rs.code() < rt.code());
-  GenInstrImmediate(DADDI, rs, rt, offset);
+  DCHECK(rs.code() != rt.code() && rs.code() != 0 && rt.code() != 0);
+  if (rs.code() < rt.code()) {
+    GenInstrImmediate(DADDI, rs, rt, offset);
+  } else {
+    GenInstrImmediate(DADDI, rt, rs, offset);
+  }
+  EmittedCompactBranchInstruction();
 }
 
 
 void Assembler::bnezc(Register rs, int32_t offset) {
   DCHECK(IsMipsArchVariant(kMips32r6));
   DCHECK(!(rs.is(zero_reg)));
-  Instr instr = POP76 | (rs.code() << kRsShift) | offset;
+  Instr instr = POP76 | (rs.code() << kRsShift) | (offset & kImm21Mask);
   emit(instr);
+  EmittedCompactBranchInstruction();
 }
 
 
 void Assembler::j(int32_t target) {
 #if DEBUG
   // Get pc of delay slot.
   uint32_t ipc = reinterpret_cast<uint32_t>(pc_ + 1 * kInstrSize);
   bool in_range = ((ipc ^ static_cast<uint32_t>(target)) >>
                    (kImm26Bits + kImmFieldShift)) == 0;
   DCHECK(in_range && ((target & 3) == 0));
@@ skipping 36 matching lines @@
   GenInstrRegister(SPECIAL, rs, zero_reg, rd, 0, JALR);
   BlockTrampolinePoolFor(1);  // For associated delay slot.
 }
 
 
 void Assembler::jic(Register rt, int16_t offset) {
   DCHECK(IsMipsArchVariant(kMips32r6));
   Instr instr = POP66 | (JIC << kRsShift) | (rt.code() << kRtShift) |
                 (offset & kImm16Mask);
   emit(instr);
+  EmittedCompactBranchInstruction();
 }
 
 
 void Assembler::jialc(Register rt, int16_t offset) {
   DCHECK(IsMipsArchVariant(kMips32r6));
-  positions_recorder()->WriteRecordedPositions();
   GenInstrImmediate(POP76, zero_reg, rt, offset);
+  EmittedCompactBranchInstruction();
 }
 
 
 // -------Data-processing-instructions---------
 
 // Arithmetic.
 
 void Assembler::addu(Register rd, Register rs, Register rt) {
   GenInstrRegister(SPECIAL, rs, rt, rd, 0, ADDU);
 }
@@ skipping 1212 matching lines @@
 }
 
 
 void Assembler::bc1t(int16_t offset, uint16_t cc) {
   DCHECK(is_uint3(cc));
   Instr instr = COP1 | BC1 | cc << 18 | 1 << 16 | (offset & kImm16Mask);
   emit(instr);
 }
 
 
-// Debugging.
 int Assembler::RelocateInternalReference(RelocInfo::Mode rmode, byte* pc,
                                          intptr_t pc_delta) {
   Instr instr = instr_at(pc);
 
   if (RelocInfo::IsInternalReference(rmode)) {
     int32_t* p = reinterpret_cast<int32_t*>(pc);
     if (*p == 0) {
       return 0;  // Number of instructions patched.
     }
     *p += pc_delta;
@@ skipping 389 matching lines @@
   if (patched) {
     CpuFeatures::FlushICache(pc + 2, sizeof(Address));
   }
 }
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_MIPS