ART: String DexCache asm fast path for ARM

In the entrypoints, before a string is looked up in the slow path (in
the intern table), I added assembly to check the dex cache and return a
string pointer if the string is already in the dex cache.

Test: test-art-host

Change-Id: I245946b3efa9c2e4fa56f761effb90963ac22ec4

diff --git a/runtime/arch/arm/quick_entrypoints_arm.S b/runtime/arch/arm/quick_entrypoints_arm.S
index 11357b5..881bebe 100644 (file)
--- a/runtime/arch/arm/quick_entrypoints_arm.S
+++ b/runtime/arch/arm/quick_entrypoints_arm.S
@@ -1030,11 +1030,37 @@ ENTRY art_quick_set64_instance
 END art_quick_set64_instance
 
     /*
-     * Entry from managed code to resolve a string, this stub will allocate a String and deliver an
-     * exception on error. On success the String is returned. R0 holds the string index. The fast
-     * path check for hit in strings cache has already been performed.
+     * Entry from managed code to resolve a string, this stub will
+     * check the dex cache for a matching string (the fast path), and if not found,
+     * it will allocate a String and deliver an exception on error.
+     * On success the String is returned. R0 holds the string index.
      */
-ONE_ARG_DOWNCALL art_quick_resolve_string, artResolveStringFromCode, RETURN_IF_RESULT_IS_NON_ZERO_OR_DELIVER
+
+ENTRY art_quick_resolve_string
+    ldr    r1, [sp]                                              @ load referrer
+    ldr    r1, [r1, #ART_METHOD_DECLARING_CLASS_OFFSET]          @ load declaring class
+    ldr    r1, [r1, #DECLARING_CLASS_DEX_CACHE_STRINGS_OFFSET]   @ load string dex cache
+    ubfx   r2, r0, #0, #STRING_DEX_CACHE_HASH_BITS
+    add    r1, r1, r2, LSL #STRING_DEX_CACHE_ELEMENT_SIZE_SHIFT
+    ldrd   r2, r3, [r1]                                    @ load index into r3 and pointer into r2
+    cmp    r0, r3
+    bne    .Lart_quick_resolve_string_slow_path
+#ifdef USE_READ_BARRIER
+    ldr    r3, [r2, MIRROR_OBJECT_LOCK_WORD_OFFSET]
+    tst    r3, #LOCK_WORD_MARK_BIT_MASK_SHIFTED
+    beq    .Lart_quick_resolve_string_slow_path
+#endif
+    mov    r0, r2
+    bx     lr
+
+.Lart_quick_resolve_string_slow_path:
+    SETUP_SAVE_REFS_ONLY_FRAME r2                                @ save callee saves in case of GC
+    mov    r1, r9                                                @ pass Thread::Current
+    mov    r3, sp
+    bl     artResolveStringFromCode                              @ (uint32_t type_idx, Method* method, Thread*)
+    RESTORE_SAVE_REFS_ONLY_FRAME
+    RETURN_IF_RESULT_IS_NON_ZERO_OR_DELIVER
+END art_quick_resolve_string
 
 // Generate the allocation entrypoints for each allocator.
 GENERATE_ALLOC_ENTRYPOINTS_FOR_EACH_ALLOCATOR