MIPS: Assembler support for internal references.

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 655 matching lines @@
   Instr instr = instr_at(pos);
   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.

[paul.l..., 2015/02/09 20:14:38]

Since you deleted the DCHECK, you need to remove this comment as well.

[balazs.kilvady, 2015/02/09 20:22:36]

Done.

-  DCHECK(IsBranch(instr) || IsJ(instr) || IsLui(instr));
   // Do NOT change this to <<2. We rely on arithmetic shifts here, assuming
   // the compiler uses arithmectic 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)) {
     Instr instr_lui = instr_at(pos + 0 * Assembler::kInstrSize);
     Instr instr_ori = instr_at(pos + 1 * Assembler::kInstrSize);
     DCHECK(IsOri(instr_ori));
     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 {
+  } else if (IsJ(instr)) {
     int32_t imm28 = (instr & static_cast<int32_t>(kImm26Mask)) << 2;
     if (imm28 == 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);
       instr_address &= kImm28Mask;
       int32_t delta = instr_address - imm28;
       DCHECK(pos > delta);
       return pos - delta;
     }
+  } else {  // IsLabel(instr)
+    int32_t imm28 = (instr & static_cast<int32_t>(kImm26Mask)) << 2;
+    if (imm28 == kEndOfJumpChain) {
+      // EndOfChain sentinel is returned directly, not relative to pc or pos.
+      return kEndOfChain;
+    } else {
+      return pos + imm28;
+    }
   }
 }
 
 
 void Assembler::target_at_put(int32_t pos, int32_t target_pos) {
   Instr instr = instr_at(pos);
   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) || IsJ(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 instr_lui = instr_at(pos + 0 * Assembler::kInstrSize);
     Instr instr_ori = instr_at(pos + 1 * Assembler::kInstrSize);
     DCHECK(IsOri(instr_ori));
     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 {
+  } else if (IsJ(instr)) {
     uint32_t imm28 = reinterpret_cast<uint32_t>(buffer_) + target_pos;
     imm28 &= kImm28Mask;
     DCHECK((imm28 & 3) == 0);
 
     instr &= ~kImm26Mask;
     uint32_t imm26 = imm28 >> 2;
     DCHECK(is_uint26(imm26));
 
     instr_at_put(pos, instr | (imm26 & kImm26Mask));
+  } else {
+    uint32_t imm = reinterpret_cast<uint32_t>(buffer_) + target_pos;
+    instr_at_put(pos, imm);
   }
 }
 
 
 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 34 matching lines @@
           trampoline_pos = get_trampoline_entry(fixup_pos);
           CHECK(trampoline_pos != kInvalidSlotPos);
         }
         DCHECK((trampoline_pos - fixup_pos) <= kMaxBranchOffset);
         target_at_put(fixup_pos, trampoline_pos);
         fixup_pos = trampoline_pos;
         dist = pos - fixup_pos;
       }
       target_at_put(fixup_pos, pos);
     } else {
-      DCHECK(IsJ(instr) || IsLui(instr) || IsEmittedConstant(instr));
       target_at_put(fixup_pos, pos);
     }
   }
   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 1521 matching lines @@
   if (FLAG_trace_deopt) {
     EnsureSpace ensure_space(this);
     RecordRelocInfo(RelocInfo::POSITION, raw_position);
     RecordRelocInfo(RelocInfo::DEOPT_REASON, reason);
   }
 }
 
 
 int Assembler::RelocateInternalReference(byte* pc, intptr_t pc_delta) {
   Instr instr = instr_at(pc);
-  DCHECK(IsJ(instr) || IsLui(instr));
   if (IsLui(instr)) {
     Instr instr_lui = instr_at(pc + 0 * Assembler::kInstrSize);
     Instr instr_ori = instr_at(pc + 1 * Assembler::kInstrSize);
     DCHECK(IsOri(instr_ori));
     int32_t imm = (instr_lui & static_cast<int32_t>(kImm16Mask)) << kLuiShift;
     imm |= (instr_ori & static_cast<int32_t>(kImm16Mask));
     if (imm == kEndOfJumpChain) {
       return 0;  // Number of instructions patched.
     }
     imm += pc_delta;
     DCHECK((imm & 3) == 0);
 
     instr_lui &= ~kImm16Mask;
     instr_ori &= ~kImm16Mask;
 
     instr_at_put(pc + 0 * Assembler::kInstrSize,
                  instr_lui | ((imm >> kLuiShift) & kImm16Mask));
     instr_at_put(pc + 1 * Assembler::kInstrSize,
                  instr_ori | (imm & kImm16Mask));
     return 2;  // Number of instructions patched.
-  } else {
+  } else if (IsJ(instr)) {
     uint32_t imm28 = (instr & static_cast<int32_t>(kImm26Mask)) << 2;
     if (static_cast<int32_t>(imm28) == kEndOfJumpChain) {
       return 0;  // Number of instructions patched.
     }
     imm28 += pc_delta;
     imm28 &= kImm28Mask;
     DCHECK((imm28 & 3) == 0);
 
     instr &= ~kImm26Mask;
     uint32_t imm26 = imm28 >> 2;
     DCHECK(is_uint26(imm26));
 
     instr_at_put(pc, instr | (imm26 & kImm26Mask));
     return 1;  // Number of instructions patched.
+  } else {  // IsLabel(instr)
+    int32_t* p = reinterpret_cast<int32_t*>(pc);
+    uint32_t imm28 = (instr & static_cast<int32_t>(kImm26Mask)) << 2;
+    if (static_cast<int32_t>(imm28) == kEndOfJumpChain) {
+      return 0;  // Number of instructions patched.
+    }
+    *p += pc_delta;
+    return 1;  // Number of instructions patched.
   }
 }
 
 
 void Assembler::GrowBuffer() {
   if (!own_buffer_) FATAL("external code buffer is too small");
 
   // Compute new buffer size.
   CodeDesc desc;  // The new buffer.
   if (buffer_size_ < 1 * MB) {
@@ skipping 44 matching lines @@
 }
 
 
 void Assembler::dd(uint32_t data) {
   CheckBuffer();
   *reinterpret_cast<uint32_t*>(pc_) = data;
   pc_ += sizeof(uint32_t);
 }
 
 
+void Assembler::dd(Label* label) {
+  CheckBuffer();
+  RecordRelocInfo(RelocInfo::INTERNAL_REFERENCE);
+  if (label->is_bound()) {
+    uint32_t data = reinterpret_cast<uint32_t>(buffer_ + label->pos());
+    *reinterpret_cast<uint32_t*>(pc_) = data;
+    pc_ += sizeof(uint32_t);
+  } else {
+    int target_pos;
+    if (label->is_linked()) {
+      // Point to previous instruction that uses the link.
+      target_pos = label->pos();
+    } else {
+      // First entry of the link chain points to itself.
+      target_pos = pc_offset();
+    }
+    label->link_to(pc_offset());
+    // Encode internal reference to unbound label. We set the least significant
+    // bit to distinguish unbound internal references in GrowBuffer() below.
+    int diff = target_pos - pc_offset();
+    DCHECK_EQ(0, diff & 3);
+    int imm26 = diff >> 2;
+    DCHECK(is_int26(imm26));
+    // Emit special LABEL instruction.
+    emit(LABEL | (imm26 & kImm26Mask));
+  }
+}
+
+
 void Assembler::emit_code_stub_address(Code* stub) {
   CheckBuffer();
   *reinterpret_cast<uint32_t*>(pc_) =
       reinterpret_cast<uint32_t>(stub->instruction_start());
   pc_ += sizeof(uint32_t);
 }
 
 
 void Assembler::RecordRelocInfo(RelocInfo::Mode rmode, intptr_t data) {
   // We do not try to reuse pool constants.
@@ skipping 278 matching lines @@
 void Assembler::PopulateConstantPool(ConstantPoolArray* constant_pool) {
   // No out-of-line constant pool support.
   DCHECK(!FLAG_enable_ool_constant_pool);
   return;
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_MIPS