ARM64: Introduce a version of ADR handling distant targets.

src/arm64/assembler-arm64.cc

Index: src/arm64/assembler-arm64.cc
diff --git a/src/arm64/assembler-arm64.cc b/src/arm64/assembler-arm64.cc
index 8bee92ccc273a87b1e319481ef0697063c7f4075..2e3c5492164a40663ee55c85862316cbb4e333c5 100644
--- a/src/arm64/assembler-arm64.cc
+++ b/src/arm64/assembler-arm64.cc
@@ -2808,6 +2808,76 @@ void Assembler::PopulateConstantPool(ConstantPoolArray* constant_pool) {
 }
 
 
+void PatchingAssembler::MovInt64(const Register& rd, int64_t imm) {
+  Label start;
+  bind(&start);
+
+  ASSERT(rd.Is64Bits());
+  ASSERT(!rd.IsSP());
+
+  for (unsigned i = 0; i < (rd.SizeInBits() / 16); i++) {
+    uint64_t imm16 = (imm >> (16 * i)) & 0xffffL;
+    movk(rd, imm16, 16 * i);
+  }
+
+  ASSERT(SizeOfCodeGeneratedSince(&start) ==
+         kMovInt64NInstrs * kInstructionSize);
+}
+
+
+void PatchingAssembler::PatchAdrFar(Instruction* target) {
+  // The code at the current instruction should be:
+  //   adr  rd, 0
+  //   nop  (adr_far)
+  //   nop  (adr_far)
+  //   nop  (adr_far)
+  //   movz scratch, 0
+  //   add  rd, rd, scratch
+
+  // Verify the expected code.
+  Instruction* expected_adr = InstructionAt(0);
+  CHECK(expected_adr->IsAdr() && (expected_adr->ImmPCRel() == 0));
+  int rd_code = expected_adr->Rd();
+  for (int i = 0; i < kAdrFarPatchableNNops; ++i) {
+    CHECK(InstructionAt((i + 1) * kInstructionSize)->IsNop(ADR_FAR_NOP));
+  }
+  Instruction* expected_movz =
+      InstructionAt((kAdrFarPatchableNInstrs - 2) * kInstructionSize);
+  CHECK(expected_movz->IsMovz() &&
+        (expected_movz->ImmMoveWide() == 0) &&
+        (expected_movz->ShiftMoveWide() == 0));
+  int scratch_code = expected_movz->Rd();
+  Instruction* expected_add =
+      InstructionAt((kAdrFarPatchableNInstrs - 1) * kInstructionSize);
+  CHECK(expected_add->IsAddSubShifted() &&
+        (expected_add->Mask(AddSubOpMask) == ADD) &&
+        expected_add->SixtyFourBits() &&
+        (expected_add->Rd() == rd_code) && (expected_add->Rn() == rd_code) &&
+        (expected_add->Rm() == scratch_code) &&
+        (static_cast<Shift>(expected_add->ShiftDP()) == LSL) &&
+        (expected_add->ImmDPShift() == 0));
+
+  // Patch to load the correct address.
+  Label start;
+  bind(&start);
+  Register rd = Register::XRegFromCode(rd_code);
+  // If the target is in range, we only patch the adr. Otherwise we patch the
+  // nops with fixup instructions.
+  int target_offset = expected_adr->DistanceTo(target);
+  if (Instruction::IsValidPCRelOffset(target_offset)) {
+    adr(rd, target_offset);
+    for (int i = 0; i < kAdrFarPatchableNInstrs - 2; ++i) {
+      nop(ADR_FAR_NOP);
+    }
+  } else {
+    Register scratch = Register::XRegFromCode(scratch_code);
+    adr(rd, 0);
+    MovInt64(scratch, target_offset);
+    add(rd, rd, scratch);
+  }
+}
+
+
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_ARM64