[compiler-rt] 6fab808 - [NFC][sanitizer] Combine MSAN data in single field

[Vitaly Buka via llvm-commits]

Author: Vitaly Buka
Date: 2021-10-05T12:34:02-07:00
New Revision: 6fab808f6f1bc935d7a74ff2ab002ccfa7dd806c

URL: https://github.com/llvm/llvm-project/commit/6fab808f6f1bc935d7a74ff2ab002ccfa7dd806c
DIFF: https://github.com/llvm/llvm-project/commit/6fab808f6f1bc935d7a74ff2ab002ccfa7dd806c.diff

LOG: [NFC][sanitizer] Combine MSAN data in single field

Reviewed By: morehouse

Differential Revision: https://reviews.llvm.org/D111118

Added: 
    

Modified: 
    compiler-rt/lib/sanitizer_common/sanitizer_stackdepot.cpp

Removed: 
    


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diff  --git a/compiler-rt/lib/sanitizer_common/sanitizer_stackdepot.cpp b/compiler-rt/lib/sanitizer_common/sanitizer_stackdepot.cpp
index c71b0a17496a2..2365beefd0fd9 100644
--- a/compiler-rt/lib/sanitizer_common/sanitizer_stackdepot.cpp
+++ b/compiler-rt/lib/sanitizer_common/sanitizer_stackdepot.cpp
@@ -21,24 +21,21 @@ namespace __sanitizer {
 struct StackDepotNode {
   StackDepotNode *link;
   u32 id;
-  atomic_uint32_t hash_and_use_count; // hash_bits : 12; use_count : 20;
+  u32 stack_hash;
   u32 size;
-  u32 tag;
+  atomic_uint32_t tag_and_use_count;  // tag : 12 high bits; use_count : 20;
   uptr stack[1];  // [size]
 
   static const u32 kTabSizeLog = SANITIZER_ANDROID ? 16 : 20;
-  // Lower kTabSizeLog bits are equal for all items in one bucket.
-  // We use these bits to store the per-stack use counter.
-  static const u32 kUseCountBits = kTabSizeLog;
+  static const u32 kUseCountBits = 20;
   static const u32 kMaxUseCount = 1 << kUseCountBits;
   static const u32 kUseCountMask = (1 << kUseCountBits) - 1;
-  static const u32 kHashMask = ~kUseCountMask;
 
   typedef StackTrace args_type;
   bool eq(u32 hash, const args_type &args) const {
-    u32 hash_bits =
-        atomic_load(&hash_and_use_count, memory_order_relaxed) & kHashMask;
-    if ((hash & kHashMask) != hash_bits || args.size != size || args.tag != tag)
+    u32 tag =
+        atomic_load(&tag_and_use_count, memory_order_relaxed) >> kUseCountBits;
+    if (stack_hash != hash || args.size != size || args.tag != tag)
       return false;
     uptr i = 0;
     for (; i < size; i++) {
@@ -58,12 +55,16 @@ struct StackDepotNode {
     return args.size > 0 && args.trace;
   }
   void store(const args_type &args, u32 hash) {
-    atomic_store(&hash_and_use_count, hash & kHashMask, memory_order_relaxed);
+    CHECK_EQ(args.tag & (~kUseCountMask >> kUseCountBits), args.tag);
+    atomic_store(&tag_and_use_count, args.tag << kUseCountBits,
+                 memory_order_relaxed);
+    stack_hash = hash;
     size = args.size;
-    tag = args.tag;
     internal_memcpy(stack, args.trace, size * sizeof(uptr));
   }
   args_type load() const {
+    u32 tag =
+        atomic_load(&tag_and_use_count, memory_order_relaxed) >> kUseCountBits;
     return args_type(&stack[0], size, tag);
   }
   StackDepotHandle get_handle() { return StackDepotHandle(this); }
@@ -75,12 +76,12 @@ COMPILER_CHECK(StackDepotNode::kMaxUseCount == (u32)kStackDepotMaxUseCount);
 
 u32 StackDepotHandle::id() { return node_->id; }
 int StackDepotHandle::use_count() {
-  return atomic_load(&node_->hash_and_use_count, memory_order_relaxed) &
+  return atomic_load(&node_->tag_and_use_count, memory_order_relaxed) &
          StackDepotNode::kUseCountMask;
 }
 void StackDepotHandle::inc_use_count_unsafe() {
   u32 prev =
-      atomic_fetch_add(&node_->hash_and_use_count, 1, memory_order_relaxed) &
+      atomic_fetch_add(&node_->tag_and_use_count, 1, memory_order_relaxed) &
       StackDepotNode::kUseCountMask;
   CHECK_LT(prev + 1, StackDepotNode::kMaxUseCount);
 }