Use `std::string_view` for `ClassTable` operations.

Use `std::string_view` instead of `const char*` descriptor.
This uses faster `memcmp` instead of the slower`strcmp` for
descriptor comparison.

Note that the `ScopedTrace` passes `const char*` across the
`libartpalette` boundary, so we cannot easily replace the
`const char* descriptor` with `std::string_view descriptor`
in certain `ClassLinker` functions because we actually need
to pass a null-terminated string and the `string_view` API
does not technically guarantee null-terminated data.
Therefore we resort to explicitly passing around the
descriptor and its length as separate arguments.

Test: m test-art-host-gtest
Test: testrunner.py --host --optimizing
Bug: 181943478
Bug: 338123769
Change-Id: Ie3fa251390acc582c54b4686d18696eb89b32361

1 files changed, 4 insertions, 3 deletions

diff --git a/runtime/class_table.h b/runtime/class_table.h
index 3374622f00..64ae758208 100644
--- a/runtime/class_table.h
+++ b/runtime/class_table.h
@@ -114,14 +114,15 @@ class ClassTable {
     static constexpr uint32_t kHashMask = kObjectAlignment - 1;
   };
 
-  using DescriptorHashPair = std::pair<const char*, uint32_t>;
+  using DescriptorHashPair = std::pair<std::string_view, uint32_t>;
 
   class ClassDescriptorHash {
    public:
     // uint32_t for cross compilation.
+    // NO_THREAD_SAFETY_ANALYSIS: Used from unannotated `HashSet<>` functions.
     uint32_t operator()(const TableSlot& slot) const NO_THREAD_SAFETY_ANALYSIS;
     // uint32_t for cross compilation.
-    uint32_t operator()(const DescriptorHashPair& pair) const NO_THREAD_SAFETY_ANALYSIS;
+    uint32_t operator()(const DescriptorHashPair& pair) const;
   };
 
   class ClassDescriptorEquals {
@@ -221,7 +222,7 @@ class ClassTable {
       REQUIRES_SHARED(Locks::mutator_lock_);
 
   // Return the first class that matches the descriptor. Returns null if there are none.
-  ObjPtr<mirror::Class> Lookup(const char* descriptor, size_t hash)
+  ObjPtr<mirror::Class> Lookup(std::string_view descriptor, size_t hash)
       REQUIRES(!lock_)
       REQUIRES_SHARED(Locks::mutator_lock_);