[asan] start compacting the allocator header, the goal is to make it 16 bytes w/o losing any information

llvm-svn: 158072

4 files changed, 23 insertions, 11 deletions

diff --git a/compiler-rt/lib/asan/asan_allocator.cc b/compiler-rt/lib/asan/asan_allocator.cc
index afa1dc0a8d8..48ed6518d53 100644
--- a/compiler-rt/lib/asan/asan_allocator.cc
+++ b/compiler-rt/lib/asan/asan_allocator.cc
@@ -150,19 +150,19 @@ static u8 *MmapNewPagesAndPoisonShadow(uptr size) {
 //
 // The magic numbers for the enum values are taken randomly.
 enum {
-  CHUNK_AVAILABLE  = 0x573B,
-  CHUNK_ALLOCATED  = 0x3204,
-  CHUNK_QUARANTINE = 0x1978,
-  CHUNK_MEMALIGN   = 0xDC68,
+  CHUNK_AVAILABLE  = 0x57,
+  CHUNK_ALLOCATED  = 0x32,
+  CHUNK_QUARANTINE = 0x19,
+  CHUNK_MEMALIGN   = 0xDC,
 };
 
 struct ChunkBase {
-  u16   chunk_state;
-  u8    size_class;
-  u32   offset;  // User-visible memory starts at this+offset (beg()).
-  s32    alloc_tid;
-  s32    free_tid;
-  uptr     used_size;  // Size requested by the user.
+  u8   chunk_state;
+  u8   size_class;
+  u32  offset;  // User-visible memory starts at this+offset (beg()).
+  s32  alloc_tid;
+  s32  free_tid;
+  uptr used_size;  // Size requested by the user.
   AsanChunk *next;
 
   uptr   beg() { return (uptr)this + offset; }
@@ -708,7 +708,7 @@ static void Deallocate(u8 *ptr, AsanStackTrace *stack) {
   AsanChunk *m = PtrToChunk((uptr)ptr);
 
   // Flip the state atomically to avoid race on double-free.
-  u16 old_chunk_state = AtomicExchange(&m->chunk_state, CHUNK_QUARANTINE);
+  u8 old_chunk_state = AtomicExchange(&m->chunk_state, CHUNK_QUARANTINE);
 
   if (old_chunk_state == CHUNK_QUARANTINE) {
     AsanReport("ERROR: AddressSanitizer attempting double-free on %p:\n", ptr);
diff --git a/compiler-rt/lib/asan/asan_internal.h b/compiler-rt/lib/asan/asan_internal.h
index 63bed97a5ed..48818a1b134 100644
--- a/compiler-rt/lib/asan/asan_internal.h
+++ b/compiler-rt/lib/asan/asan_internal.h
@@ -144,6 +144,7 @@ void InstallSignalHandlers();
 uptr GetThreadSelf();
 int AtomicInc(int *a);
 u16 AtomicExchange(u16 *a, u16 new_val);
+u8 AtomicExchange(u8 *a, u8 new_val);
 
 // Wrapper for TLS/TSD.
 void AsanTSDInit(void (*destructor)(void *tsd));
diff --git a/compiler-rt/lib/asan/asan_posix.cc b/compiler-rt/lib/asan/asan_posix.cc
index de715c53a64..1903bc7092c 100644
--- a/compiler-rt/lib/asan/asan_posix.cc
+++ b/compiler-rt/lib/asan/asan_posix.cc
@@ -186,6 +186,10 @@ u16 AtomicExchange(u16 *a, u16 new_val) {
   return __sync_lock_test_and_set(a, new_val);
 }
 
+u8 AtomicExchange(u8 *a, u8 new_val) {
+  return __sync_lock_test_and_set(a, new_val);
+}
+
 void SortArray(uptr *array, uptr size) {
   std::sort(array, array + size);
 }
diff --git a/compiler-rt/lib/asan/asan_win.cc b/compiler-rt/lib/asan/asan_win.cc
index 609f3d4322f..8e49edafd8c 100644
--- a/compiler-rt/lib/asan/asan_win.cc
+++ b/compiler-rt/lib/asan/asan_win.cc
@@ -219,6 +219,13 @@ u16 AtomicExchange(u16 *a, u16 new_val) {
   return new_val;
 }
 
+u16 AtomicExchange(u16 *a, u16 new_val) {
+  // FIXME: can we do this with a proper xchg intrinsic?
+  u8 t = *a;
+  *a = new_val;
+  return t;
+}
+
 const char* AsanGetEnv(const char* name) {
   static char env_buffer[32767] = {};