revise assembly test for the _mi_threadid(); fix issue #495 with musl libc on arm; test specifically for bionic libc on Android

Author: daanx

include/mimalloc-internal.h

@@ -698,90 +698,104 @@ static inline size_t _mi_os_numa_node_count(void) {
 // -------------------------------------------------------------------
 // Getting the thread id should be performant as it is called in the
 // fast path of `_mi_free` and we specialize for various platforms.
+// We only require _mi_threadid() to return a unique id for each thread.
 // -------------------------------------------------------------------
 #if defined(_WIN32)
+
 #define WIN32_LEAN_AND_MEAN
 #include <windows.h>
 static inline mi_threadid_t _mi_thread_id(void) mi_attr_noexcept {
   // Windows: works on Intel and ARM in both 32- and 64-bit
   return (uintptr_t)NtCurrentTeb();
 }
 
-#elif defined(__GNUC__) && \
-      (defined(__x86_64__) || defined(__i386__) || defined(__aarch64__))
-
+// We use assembly for a fast thread id on the main platforms. The TLS layout depends on 
+// both the OS and libc implementation so we use specific tests for each main platform.
+// If you test on another platform and it works please send a PR :-)
 // see also https://akkadia.org/drepper/tls.pdf for more info on the TLS register.
+#elif defined(__GNUC__) && ( \
+           (defined(__GLIBC__)   && (defined(__x86_64__) || defined(__i386__) || defined(__arm__) || defined(__aarch64__))) \
+        || (defined(__APPLE__)   && (defined(__x86_64__) || defined(__aarch64__))) \
+        || (defined(__BIONIC__)  && (defined(__x86_64__) || defined(__i386__) || defined(__arm__) || defined(__aarch64__))) \
+        || (defined(__FreeBSD__) && (defined(__x86_64__) || defined(__i386__) || defined(__aarch64__))) \
+      )
+
 static inline void* mi_tls_slot(size_t slot) mi_attr_noexcept {
   void* res;
   const size_t ofs = (slot*sizeof(void*));
-#if defined(__i386__)
-  __asm__("movl %%gs:%1, %0" : "=r" (res) : "m" (*((void**)ofs)) : );  // x86 32-bit always uses GS
-#elif defined(__APPLE__) && defined(__x86_64__)
-  __asm__("movq %%gs:%1, %0" : "=r" (res) : "m" (*((void**)ofs)) : );  // x86_64 macOSX uses GS
-#elif defined(__x86_64__) && (MI_INTPTR_SIZE==4)
-  __asm__("movl %%fs:%1, %0" : "=r" (res) : "m" (*((void**)ofs)) : );  // x32 ABI
-#elif defined(__x86_64__)
-  __asm__("movq %%fs:%1, %0" : "=r" (res) : "m" (*((void**)ofs)) : );  // x86_64 Linux, BSD uses FS
-#elif defined(__arm__)   // arm32: defined but currently not used (see issue #495)
-  void** tcb; MI_UNUSED(ofs);
-  __asm__ volatile ("mrc p15, 0, %0, c13, c0, 3\nbic %0, %0, #3" : "=r" (tcb));
-  res = tcb[slot];
-#elif defined(__aarch64__)
-  void** tcb; MI_UNUSED(ofs);
-  #if defined(__APPLE__) // M1, issue #343
-  __asm__ volatile ("mrs %0, tpidrro_el0" : "=r" (tcb));
-  tcb = (void**)((uintptr_t)tcb & ~0x07UL);  // clear lower 3 bits
-  #else
-  __asm__ volatile ("mrs %0, tpidr_el0" : "=r" (tcb));
+  #if defined(__i386__)
+    __asm__("movl %%gs:%1, %0" : "=r" (res) : "m" (*((void**)ofs)) : );  // x86 32-bit always uses GS
+  #elif defined(__APPLE__) && defined(__x86_64__)
+    __asm__("movq %%gs:%1, %0" : "=r" (res) : "m" (*((void**)ofs)) : );  // x86_64 macOSX uses GS
+  #elif defined(__x86_64__) && (MI_INTPTR_SIZE==4)
+    __asm__("movl %%fs:%1, %0" : "=r" (res) : "m" (*((void**)ofs)) : );  // x32 ABI
+  #elif defined(__x86_64__)
+    __asm__("movq %%fs:%1, %0" : "=r" (res) : "m" (*((void**)ofs)) : );  // x86_64 Linux, BSD uses FS
+  #elif defined(__arm__)
+    void** tcb; MI_UNUSED(ofs);
+    __asm__ volatile ("mrc p15, 0, %0, c13, c0, 3\nbic %0, %0, #3" : "=r" (tcb));
+    res = tcb[slot];
+  #elif defined(__aarch64__)
+    void** tcb; MI_UNUSED(ofs);
+    #if defined(__APPLE__) // M1, issue #343
+    __asm__ volatile ("mrs %0, tpidrro_el0\nbic %0, %0, #7" : "=r" (tcb));
+    #else
+    __asm__ volatile ("mrs %0, tpidr_el0" : "=r" (tcb));
+    #endif
+    res = tcb[slot];
   #endif
-  res = tcb[slot];
-#endif
   return res;
 }
 
-// setting a tls slot is only used on macOSX for now
+// setting a tls slot is only used on macOS for now
 static inline void mi_tls_slot_set(size_t slot, void* value) mi_attr_noexcept {
   const size_t ofs = (slot*sizeof(void*));
-#if defined(__i386__)
-  __asm__("movl %1,%%gs:%0" : "=m" (*((void**)ofs)) : "rn" (value) : );  // 32-bit always uses GS
-#elif defined(__APPLE__) && defined(__x86_64__)
-  __asm__("movq %1,%%gs:%0" : "=m" (*((void**)ofs)) : "rn" (value) : );  // x86_64 macOSX uses GS
-#elif defined(__x86_64__) && (MI_INTPTR_SIZE==4)
-  __asm__("movl %1,%%fs:%0" : "=m" (*((void**)ofs)) : "rn" (value) : );  // x32 ABI
-#elif defined(__x86_64__)
-  __asm__("movq %1,%%fs:%0" : "=m" (*((void**)ofs)) : "rn" (value) : );  // x86_64 Linux, BSD uses FS
-#elif defined(__arm__)
-  void** tcb; MI_UNUSED(ofs);
-  __asm__ volatile ("mrc p15, 0, %0, c13, c0, 3\nbic %0, %0, #3" : "=r" (tcb));
-  tcb[slot] = value;
-#elif defined(__aarch64__)
-  void** tcb; MI_UNUSED(ofs);
-  #if defined(__APPLE__) // M1, issue #343
-  __asm__ volatile ("mrs %0, tpidrro_el0" : "=r" (tcb));
-  tcb = (void**)((uintptr_t)tcb & ~0x07UL);  // clear lower 3 bits
-  #else
-  __asm__ volatile ("mrs %0, tpidr_el0" : "=r" (tcb));
+  #if defined(__i386__)
+    __asm__("movl %1,%%gs:%0" : "=m" (*((void**)ofs)) : "rn" (value) : );  // 32-bit always uses GS
+  #elif defined(__APPLE__) && defined(__x86_64__)
+    __asm__("movq %1,%%gs:%0" : "=m" (*((void**)ofs)) : "rn" (value) : );  // x86_64 macOS uses GS
+  #elif defined(__x86_64__) && (MI_INTPTR_SIZE==4)
+    __asm__("movl %1,%%fs:%0" : "=m" (*((void**)ofs)) : "rn" (value) : );  // x32 ABI
+  #elif defined(__x86_64__)
+    __asm__("movq %1,%%fs:%0" : "=m" (*((void**)ofs)) : "rn" (value) : );  // x86_64 Linux, BSD uses FS
+  #elif defined(__arm__)
+    void** tcb; MI_UNUSED(ofs);
+    __asm__ volatile ("mrc p15, 0, %0, c13, c0, 3\nbic %0, %0, #3" : "=r" (tcb));
+    tcb[slot] = value;
+  #elif defined(__aarch64__)
+    void** tcb; MI_UNUSED(ofs);
+    #if defined(__APPLE__) // M1, issue #343
+    __asm__ volatile ("mrs %0, tpidrro_el0\nbic %0, %0, #7" : "=r" (tcb));
+    #else
+    __asm__ volatile ("mrs %0, tpidr_el0" : "=r" (tcb));
+    #endif
+    tcb[slot] = value;
   #endif
-  tcb[slot] = value;
-#endif
 }
 
 static inline mi_threadid_t _mi_thread_id(void) mi_attr_noexcept {
-#if defined(__ANDROID__) && (defined(__arm__) || defined(__aarch64__))
-  // issue #384, #495: on arm Android, slot 1 is the thread ID (pointer to pthread internal struct) 
-  return (uintptr_t)mi_tls_slot(1);
-#else
-  // in all our other targets, slot 0 is the pointer to the thread control block
-  return (uintptr_t)mi_tls_slot(0);
-#endif
+  #if defined(__BIONIC__)
+    // issue #384, #495: on the Bionic libc (Android), slot 1 is the thread id
+    // see: https://github.com/aosp-mirror/platform_bionic/blob/c44b1d0676ded732df4b3b21c5f798eacae93228/libc/platform/bionic/tls_defines.h#L86
+    return (uintptr_t)mi_tls_slot(1);
+  #else
+    // in all our other targets, slot 0 is the thread id
+    // glibc: https://sourceware.org/git/?p=glibc.git;a=blob_plain;f=sysdeps/x86_64/nptl/tls.h
+    // apple: https://github.com/apple/darwin-xnu/blob/main/libsyscall/os/tsd.h#L36
+    return (uintptr_t)mi_tls_slot(0);
+  #endif
 }
+
 #else
-// otherwise use portable C
+
+// otherwise use portable C, taking the address of a thread local variable (this is still very fast on most platforms).
 static inline mi_threadid_t _mi_thread_id(void) mi_attr_noexcept {
   return (uintptr_t)&_mi_heap_default;
 }
+
 #endif
 
+
 // -----------------------------------------------------------------------
 // Count bits: trailing or leading zeros (with MI_INTPTR_BITS on all zero)
 // -----------------------------------------------------------------------