Thumb2 Backend: Thumb2 changes for Deoptimization and Code Aging

src/arm/codegen-arm.cc

Index: src/arm/codegen-arm.cc
diff --git a/src/arm/codegen-arm.cc b/src/arm/codegen-arm.cc
index 1bcf3e3a605b051571dc9c51912264c65b90e14e..fff8d5e71553ad375785e1dea1dbd39c7cdfa969 100644
--- a/src/arm/codegen-arm.cc
+++ b/src/arm/codegen-arm.cc
@@ -826,6 +826,7 @@ void MathExpGenerator::EmitMathExp(MacroAssembler* masm,
 
 // add(r0, pc, Operand(-8))
 static const uint32_t kCodeAgePatchFirstInstruction = 0xe24f0008;
+static const uint32_t kThumbCodeAgePatchFirstInstruction = 0x3f2af;
 
 static byte* GetNoCodeAgeSequence(uint32_t* length) {
   // The sequence of instructions that is patched out for aging code is the
@@ -846,19 +847,43 @@ static byte* GetNoCodeAgeSequence(uint32_t* length) {
 }
 
 
-bool Code::IsYoungSequence(byte* sequence) {
+static byte* GetThumbNoCodeAgeSequence(uint32_t* length) {
+  // The sequence of instructions that is patched out for aging code is the
+  // following boilerplate stack-building prologue that is found in FUNCTIONS
+  static bool initialized = false;
+  static uint32_t sequence[kNoCodeAgeSequenceLength];
+  byte* byte_sequence = reinterpret_cast<byte*>(sequence);
+  *length = kNoCodeAgeSequenceLength * Assembler::kInstrSize;
+  if (!initialized) {
+    CodePatcher patcher(byte_sequence, kNoCodeAgeSequenceLength);
+    PredictableCodeSizeScope scope(patcher.masm(), *length);
+    patcher.masm()->set_thumb_mode();
+    patcher.masm()->stm(db_w, sp, r1.bit() | cp.bit() | fp.bit() | lr.bit());
+    patcher.masm()->nop(ip.code());
+    patcher.masm()->nop(ip.code());
+    patcher.masm()->add(fp, sp, Operand(2 * kPointerSize));
+    initialized = true;
+  }
+  return byte_sequence;
+}
+
+
+bool Code::IsYoungSequence(byte* sequence, bool thumb_mode) {
   uint32_t young_length;
-  byte* young_sequence = GetNoCodeAgeSequence(&young_length);
+  byte* young_sequence = thumb_mode ? GetThumbNoCodeAgeSequence(&young_length) :
+                                      GetNoCodeAgeSequence(&young_length);
   bool result = !memcmp(sequence, young_sequence, young_length);
   ASSERT(result ||
-         Memory::uint32_at(sequence) == kCodeAgePatchFirstInstruction);
+         Memory::uint32_at(sequence) == kCodeAgePatchFirstInstruction ||
+         Memory::uint32_at(sequence) == kThumbCodeAgePatchFirstInstruction);
   return result;
 }
 
 
 void Code::GetCodeAgeAndParity(byte* sequence, Age* age,
-                               MarkingParity* parity) {
-  if (IsYoungSequence(sequence)) {
+                               MarkingParity* parity,
+                               bool thumb_mode) {
+  if (IsYoungSequence(sequence, thumb_mode)) {
     *age = kNoAge;
     *parity = NO_MARKING_PARITY;
   } else {
@@ -872,17 +897,29 @@ void Code::GetCodeAgeAndParity(byte* sequence, Age* age,
 
 void Code::PatchPlatformCodeAge(byte* sequence,
                                 Code::Age age,
-                                MarkingParity parity) {
+                                MarkingParity parity,
+                                bool thumb_mode) {
   uint32_t young_length;
-  byte* young_sequence = GetNoCodeAgeSequence(&young_length);
+  if (((uint32_t)sequence & 1) == 1) {
+    thumb_mode = true;
+    sequence = reinterpret_cast<byte*>((uint32_t)sequence & ~1);
+  }
+  byte* young_sequence = thumb_mode? GetThumbNoCodeAgeSequence(&young_length) :
+                                     GetNoCodeAgeSequence(&young_length);
   if (age == kNoAge) {
     CopyBytes(sequence, young_sequence, young_length);
     CPU::FlushICache(sequence, young_length);
   } else {
     Code* stub = GetCodeAgeStub(age, parity);
     CodePatcher patcher(sequence, young_length / Assembler::kInstrSize);
-    patcher.masm()->add(r0, pc, Operand(-8));
-    patcher.masm()->ldr(pc, MemOperand(pc, -4));
+    if (thumb_mode) {
+      patcher.masm()->set_thumb_mode();
+      patcher.masm()->sub(r0, pc, Operand(3));
+      patcher.masm()->ldr(pc, MemOperand(pc, 0));
+    } else {
+      patcher.masm()->sub(r0, pc, Operand(8));
+      patcher.masm()->ldr(pc, MemOperand(pc, -4));
+    }
     patcher.masm()->dd(reinterpret_cast<uint32_t>(stub->instruction_start()));
   }
 }