builtins: implement __emutls_get_address

For targets like Android that depends on libgcc's emulated thread local storage.
clang/llvm can generate calls to __emutls_get_address since
http://reviews.llvm.org/D10522 and http://reviews.llvm.org/D10524

Differential Revision: http://reviews.llvm.org/D12001

llvm-svn: 246454

compiler-rt/lib/builtins/CMakeLists.txt

@@ -139,6 +139,12 @@ set(GENERIC_SOURCES
   umodsi3.c
   umodti3.c)
 
+if(NOT WIN32)
+  set(GENERIC_SOURCES
+      ${GENERIC_SOURCES}
+      emutls.c)
+endif()
+
 if (HAVE_UNWIND_H)
   set(GENERIC_SOURCES
       ${GENERIC_SOURCES}

compiler-rt/lib/builtins/README.txt

@@ -220,7 +220,9 @@ _Unwind_Reason_Code __gcc_personality_v0(int version, _Unwind_Action actions,
 // for use with some implementations of assert() in <assert.h>
 void __eprintf(const char* format, const char* assertion_expression,
 				const char* line, const char* file);
-				
+
+// for systems with emulated thread local storage
+void* __emutls_get_address(struct __emutls_control*);
 
 
 //   Power PC specific functions

compiler-rt/lib/builtins/emutls.c

@@ -0,0 +1,181 @@
+/* ===---------- emutls.c - Implements __emutls_get_address ---------------===
+ *
+ *                     The LLVM Compiler Infrastructure
+ *
+ * This file is dual licensed under the MIT and the University of Illinois Open
+ * Source Licenses. See LICENSE.TXT for details.
+ *
+ * ===----------------------------------------------------------------------===
+ */
+#include <pthread.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "int_util.h"
+
+/* Default is not to use posix_memalign, so systems like Android
+ * can use thread local data without heavier POSIX memory allocators.
+ */
+#ifndef EMUTLS_USE_POSIX_MEMALIGN
+#define EMUTLS_USE_POSIX_MEMALIGN 0
+#endif
+
+/* For every TLS variable xyz,
+ * there is one __emutls_control variable named __emutls_v.xyz.
+ * If xyz has non-zero initial value, __emutls_v.xyz's "value"
+ * will point to __emutls_t.xyz, which has the initial value.
+ */
+typedef struct __emutls_control {
+    size_t size;  /* size of the object in bytes */
+    size_t align;  /* alignment of the object in bytes */
+    union {
+        uintptr_t index;  /* data[index-1] is the object address */
+        void* address;  /* object address, when in single thread env */
+    } object;
+    void* value;  /* null or non-zero initial value for the object */
+} __emutls_control;
+
+static inline void* emutls_memalign_alloc(size_t align, size_t size) {
+    void *base;
+#if EMUTLS_USE_POSIX_MEMALIGN
+    if (posix_memalign(&base, align, size) != 0)
+        abort();
+#else
+    #define EXTRA_ALIGN_PTR_BYTES (align - 1 + sizeof(void*))
+    char* object;
+    if ((object = malloc(EXTRA_ALIGN_PTR_BYTES + size)) == NULL)
+        abort();
+    base = (void*)(((uintptr_t)(object + EXTRA_ALIGN_PTR_BYTES))
+                    & ~(uintptr_t)(align - 1));
+
+    ((void**)base)[-1] = object;
+#endif
+    return base;
+}
+
+static inline void emutls_memalign_free(void* base) {
+#if EMUTLS_USE_POSIX_MEMALIGN
+    free(base);
+#else
+    /* The mallocated address is in ((void**)base)[-1] */
+    free(((void**)base)[-1]);
+#endif
+}
+
+/* Emulated TLS objects are always allocated at run-time. */
+static inline void* emutls_allocate_object(__emutls_control* control) {
+    /* Use standard C types, check with gcc's emutls.o. */
+    typedef unsigned int gcc_word __attribute__((mode(word)));
+    typedef unsigned int gcc_pointer __attribute__((mode(pointer)));
+    COMPILE_TIME_ASSERT(sizeof(size_t) == sizeof(gcc_word));
+    COMPILE_TIME_ASSERT(sizeof(uintptr_t) == sizeof(gcc_pointer));
+    COMPILE_TIME_ASSERT(sizeof(uintptr_t) == sizeof(void*));
+
+    size_t size = control->size;
+    size_t align = control->align;
+    if (align < sizeof(void*))
+        align = sizeof(void*);
+    /* Make sure that align is power of 2. */
+    if ((align & (align - 1)) != 0)
+        abort();
+
+    void* base = emutls_memalign_alloc(align, size);
+    if (control->value)
+        memcpy(base, control->value, size);
+    else
+        memset(base, 0, size);
+    return base;
+}
+
+static pthread_mutex_t emutls_mutex = PTHREAD_MUTEX_INITIALIZER;
+
+static size_t emutls_num_object = 0;  /* number of allocated TLS objects */
+
+typedef struct emutls_address_array {
+    uintptr_t size;  /* number of elements in the 'data' array */
+    void* data[];
+} emutls_address_array;
+
+static pthread_key_t emutls_pthread_key;
+
+static void emutls_key_destructor(void* ptr) {
+    emutls_address_array* array = (emutls_address_array*)ptr;
+    uintptr_t i;
+    for (i = 0; i < array->size; ++i) {
+        if (array->data[i])
+            emutls_memalign_free(array->data[i]);
+    }
+    free(ptr);
+}
+
+static void emutls_init(void) {
+    if (pthread_key_create(&emutls_pthread_key, emutls_key_destructor) != 0)
+        abort();
+}
+
+/* Returns control->object.index; set index if not allocated yet. */
+static inline uintptr_t emutls_get_index(__emutls_control* control) {
+    uintptr_t index = __atomic_load_n(&control->object.index, __ATOMIC_ACQUIRE);
+    if (!index) {
+        static pthread_once_t once = PTHREAD_ONCE_INIT;
+        pthread_once(&once, emutls_init);
+        pthread_mutex_lock(&emutls_mutex);
+        index = control->object.index;
+        if (!index) {
+            index = ++emutls_num_object;
+            __atomic_store_n(&control->object.index, index, __ATOMIC_RELEASE);
+        }
+        pthread_mutex_unlock(&emutls_mutex);
+    }
+    return index;
+}
+
+/* Updates newly allocated thread local emutls_address_array. */
+static inline void emutls_check_array_set_size(emutls_address_array* array,
+                                               uintptr_t size) {
+    if (array == NULL)
+        abort();
+    array->size = size;
+    pthread_setspecific(emutls_pthread_key, (void*)array);
+}
+
+/* Returns the new 'data' array size, number of elements,
+ * which must be no smaller than the given index.
+ */
+static inline uintptr_t emutls_new_data_array_size(uintptr_t index) {
+   /* Need to allocate emutls_address_array with one extra slot
+    * to store the data array size.
+    * Round up the emutls_address_array size to multiple of 16.
+    */
+    return ((index + 1 + 15) & ~((uintptr_t)15)) - 1;
+}
+
+/* Returns the thread local emutls_address_array.
+ * Extends its size if necessary to hold address at index.
+ */
+static inline emutls_address_array* emutls_get_address_array(uintptr_t index) {
+    emutls_address_array* array = pthread_getspecific(emutls_pthread_key);
+    if (array == NULL) {
+        uintptr_t new_size = emutls_new_data_array_size(index);
+        array = calloc(new_size + 1, sizeof(void*));
+        emutls_check_array_set_size(array, new_size);
+    } else if (index > array->size) {
+        uintptr_t orig_size = array->size;
+        uintptr_t new_size = emutls_new_data_array_size(index);
+        array = realloc(array, (new_size + 1) * sizeof(void*));
+        if (array)
+            memset(array->data + orig_size, 0,
+                   (new_size - orig_size) * sizeof(void*));
+        emutls_check_array_set_size(array, new_size);
+    }
+    return array;
+}
+
+void* __emutls_get_address(__emutls_control* control) {
+    uintptr_t index = emutls_get_index(control);
+    emutls_address_array* array = emutls_get_address_array(index);
+    if (array->data[index - 1] == NULL)
+        array->data[index - 1] = emutls_allocate_object(control);
+    return array->data[index - 1];
+}

compiler-rt/lib/builtins/int_util.h

@@ -26,4 +26,9 @@
 void compilerrt_abort_impl(const char *file, int line,
                            const char *function) __attribute__((noreturn));
 
+#define COMPILE_TIME_ASSERT(expr) COMPILE_TIME_ASSERT1(expr, __COUNTER__)
+#define COMPILE_TIME_ASSERT1(expr, cnt) COMPILE_TIME_ASSERT2(expr, cnt)
+#define COMPILE_TIME_ASSERT2(expr, cnt) \
+    typedef char ct_assert_##cnt[(expr) ? 1 : -1] __attribute__((unused))
+
 #endif /* INT_UTIL_H */