Encode trace action in the last two bits of method pointer

When recording method entry / exit events we used an entire entry for
recording the trace action (method enter / method exit / method unwind)
which only requires two bits. This change encodes the trace action in
the last two bits of method pointer. Given the alignment requirements of
method pointers last two bits are ensured to be 0, so it is safe to use
those bits.

Bug: 259258187
Test: art/test.py --streaming
Change-Id: I854b82f407503085dfa5304813d1d96df9ce27f3

4 files changed, 33 insertions, 18 deletions

diff --git a/compiler/optimizing/code_generator_arm64.cc b/compiler/optimizing/code_generator_arm64.cc
index d9fefc1568..d530d08b98 100644
--- a/compiler/optimizing/code_generator_arm64.cc
+++ b/compiler/optimizing/code_generator_arm64.cc
@@ -1243,13 +1243,16 @@ void InstructionCodeGeneratorARM64::GenerateMethodEntryExitHook(HInstruction* in
   __ Str(index, MemOperand(tr, trace_buffer_index_addr));
 
   Register tmp = index;
-  // Record method pointer
+  // Record method pointer and trace action.
   __ Ldr(tmp, MemOperand(sp, 0));
+  // Use last two bits to encode trace method action. For MethodEntry it is 0
+  // so no need to set the bits since they are 0 already.
+  if (instruction->IsMethodExitHook()) {
+    DCHECK_GE(ArtMethod::Alignment(kRuntimePointerSize), static_cast<size_t>(4));
+    uint32_t trace_action = 1;
+    __ Orr(tmp, tmp, Operand(trace_action));
+  }
   __ Str(tmp, MemOperand(addr, kMethodOffsetInBytes));
-  // Record the method action
-  uint32_t trace_action = instruction->IsMethodExitHook() ? 1 : 0;
-  __ Mov(tmp, Operand(trace_action));
-  __ Str(tmp, MemOperand(addr, kTraceActionOffsetInBytes));
   // Record the timestamp.
   __ Mrs(tmp, (SystemRegister)SYS_CNTVCT_EL0);
   __ Str(tmp, MemOperand(addr, kTimestampOffsetInBytes));
diff --git a/compiler/optimizing/code_generator_arm_vixl.cc b/compiler/optimizing/code_generator_arm_vixl.cc
index 99e4bda73d..ecc7a68b94 100644
--- a/compiler/optimizing/code_generator_arm_vixl.cc
+++ b/compiler/optimizing/code_generator_arm_vixl.cc
@@ -2243,13 +2243,17 @@ void InstructionCodeGeneratorARMVIXL::GenerateMethodEntryExitHook(HInstruction*
   __ Sub(index, index, kNumEntriesForWallClock);
   __ Str(index, MemOperand(tr, trace_buffer_index_addr));
 
-  // Record method pointer
+  // Record method pointer and trace action.
   __ Ldr(tmp, MemOperand(sp, 0));
+  // Use last two bits to encode trace method action. For MethodEntry it is 0
+  // so no need to set the bits since they are 0 already.
+  if (instruction->IsMethodExitHook()) {
+    DCHECK_GE(ArtMethod::Alignment(kRuntimePointerSize), static_cast<size_t>(4));
+    uint32_t trace_action = 1;
+    __ Orr(tmp, tmp, Operand(trace_action));
+  }
   __ Str(tmp, MemOperand(addr, kMethodOffsetInBytes));
-  // Record the method action
-  uint32_t trace_action = instruction->IsMethodExitHook() ? 1 : 0;
-  __ Mov(tmp, Operand(trace_action));
-  __ Str(tmp, MemOperand(addr, kTraceActionOffsetInBytes));
+
   vixl32::Register tmp1 = index;
   // See Architecture Reference Manual ARMv7-A and ARMv7-R edition section B4.1.34.
   __ Mrrc(/* lower 32-bit */ tmp,
diff --git a/compiler/optimizing/code_generator_x86.cc b/compiler/optimizing/code_generator_x86.cc
index 16aa5c1cfa..bcf5ea0907 100644
--- a/compiler/optimizing/code_generator_x86.cc
+++ b/compiler/optimizing/code_generator_x86.cc
@@ -1277,13 +1277,17 @@ void InstructionCodeGeneratorX86::GenerateMethodEntryExitHook(HInstruction* inst
   __ subl(index, Immediate(kNumEntriesForWallClock));
   __ fs()->movl(Address::Absolute(trace_buffer_index_addr), index);
 
-  // Record method pointer
+  // Record method pointer and trace action.
   Register method = index;
   __ movl(method, Address(ESP, kCurrentMethodStackOffset));
+  // Use last two bits to encode trace method action. For MethodEntry it is 0
+  // so no need to set the bits since they are 0 already.
+  if (instruction->IsMethodExitHook()) {
+    DCHECK_GE(ArtMethod::Alignment(kRuntimePointerSize), static_cast<size_t>(4));
+    uint32_t trace_action = 1;
+    __ orl(method, Immediate(trace_action));
+  }
   __ movl(Address(entry_addr, kMethodOffsetInBytes), method);
-  // Record the method action
-  uint32_t trace_action = instruction->IsMethodExitHook() ? 1 : 0;
-  __ movl(Address(entry_addr, kTraceActionOffsetInBytes), Immediate(trace_action));
   // Get the timestamp. rdtsc returns timestamp in EAX + EDX.
   __ rdtsc();
   __ movl(Address(entry_addr, kTimestampOffsetInBytes), EDX);
diff --git a/compiler/optimizing/code_generator_x86_64.cc b/compiler/optimizing/code_generator_x86_64.cc
index 15893b1fec..2e03f1f3b4 100644
--- a/compiler/optimizing/code_generator_x86_64.cc
+++ b/compiler/optimizing/code_generator_x86_64.cc
@@ -1644,13 +1644,17 @@ void InstructionCodeGeneratorX86_64::GenerateMethodEntryExitHook(HInstruction* i
   __ subq(CpuRegister(index), Immediate(kNumEntriesForWallClock));
   __ gs()->movq(Address::Absolute(trace_buffer_index_addr, /* no_rip= */ true), CpuRegister(index));
 
-  // Record method pointer
+  // Record method pointer and action.
   CpuRegister method = index;
   __ movq(CpuRegister(method), Address(CpuRegister(RSP), kCurrentMethodStackOffset));
+  // Use last two bits to encode trace method action. For MethodEntry it is 0
+  // so no need to set the bits since they are 0 already.
+  if (instruction->IsMethodExitHook()) {
+    DCHECK_GE(ArtMethod::Alignment(kRuntimePointerSize), static_cast<size_t>(4));
+    uint32_t trace_action = 1;
+    __ orq(method, Immediate(trace_action));
+  }
   __ movq(Address(entry_addr, kMethodOffsetInBytes), CpuRegister(method));
-  // Record the method action
-  uint32_t trace_action = instruction->IsMethodExitHook() ? 1 : 0;
-  __ movq(Address(entry_addr, kTraceActionOffsetInBytes), Immediate(trace_action));
   // Get the timestamp. rdtsc returns timestamp in RAX + RDX even in 64-bit architectures.
   __ rdtsc();
   __ shlq(CpuRegister(RDX), Immediate(32));