MIPS: Assembler support for internal references.

src/mips/assembler-mips.cc

Index: src/mips/assembler-mips.cc
diff --git a/src/mips/assembler-mips.cc b/src/mips/assembler-mips.cc
index 182183f547bc9f7f7bf81baffbac69c228c4cd50..48d5879d422b2e7349fb8cce5e833bead68e64ef 100644
--- a/src/mips/assembler-mips.cc
+++ b/src/mips/assembler-mips.cc
@@ -674,7 +674,6 @@ int Assembler::target_at(int32_t 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)) {
@@ -702,7 +701,7 @@ int Assembler::target_at(int32_t pos) {
       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.
@@ -714,6 +713,14 @@ int Assembler::target_at(int32_t pos) {
       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;
+    }
   }
 }
 
@@ -728,7 +735,6 @@ void Assembler::target_at_put(int32_t pos, int32_t target_pos) {
     return;
   }
 
-  DCHECK(IsBranch(instr) || IsJ(instr) || IsLui(instr));
   if (IsBranch(instr)) {
     int32_t imm18 = target_pos - (pos + kBranchPCOffset);
     DCHECK((imm18 & 3) == 0);
@@ -752,7 +758,7 @@ void Assembler::target_at_put(int32_t pos, int32_t target_pos) {
                  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);
@@ -762,6 +768,9 @@ void Assembler::target_at_put(int32_t pos, int32_t target_pos) {
     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);
   }
 }
 
@@ -816,7 +825,6 @@ void Assembler::bind_to(Label* L, int pos) {
       }
       target_at_put(fixup_pos, pos);
     } else {
-      DCHECK(IsJ(instr) || IsLui(instr) || IsEmittedConstant(instr));
       target_at_put(fixup_pos, pos);
     }
   }
@@ -2358,7 +2366,6 @@ void Assembler::RecordDeoptReason(const int reason, const int raw_position) {
 
 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);
@@ -2379,7 +2386,7 @@ int Assembler::RelocateInternalReference(byte* pc, intptr_t pc_delta) {
     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.
@@ -2394,6 +2401,14 @@ int Assembler::RelocateInternalReference(byte* pc, intptr_t pc_delta) {
 
     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.
   }
 }
 
@@ -2458,6 +2473,35 @@ void Assembler::dd(uint32_t data) {
 }
 
 
+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_) =