diff options
| -rwxr-xr-x | src/libc++/builtins.C | 47 |
1 files changed, 16 insertions, 31 deletions
diff --git a/src/libc++/builtins.C b/src/libc++/builtins.C index a336c46c3..04ea744f9 100755 --- a/src/libc++/builtins.C +++ b/src/libc++/builtins.C @@ -1,6 +1,8 @@ #include <stdint.h> #include <stdlib.h> +#include <arch/ppc.H> + void* operator new(size_t s) { return malloc(s); @@ -33,50 +35,33 @@ void operator delete[](void* p) extern "C" int __cxa_guard_acquire(volatile uint64_t* gv) { - // 0 -> uninitialized - // 1 -> locked - // 2 -> unlocked and initialized + // States: + // 0 -> uninitialized + // 1 -> locked + // 2 -> unlocked and initialized uint32_t v = __sync_val_compare_and_swap((volatile uint32_t*)gv, 0, 1); if (v == 0) return 1; if (v == 2) return 0; + + // Wait for peer thread to perform initialization (state 2). while(2 != *(volatile uint32_t*)gv); + + // Instruction barrier to ensure value is set before later loads execute. + isync(); + return 0; -/* - register volatile void* guard = gv; - register uint32_t c = 0; - - asm volatile( - "__cxa_guard_acquire_begin:" - "lwarx %0,0,%1;" // Load guard with reserve - "cmpi 0,%0,0;" // Compare with 0 - "bne+ __cxa_guard_acquire_finish;" // != 0, goto "finished" - "li %0, 1;" // Set to 1. - "stwcx. %0,0,%1;" // Store against reserve - "bne- __cxa_guard_acquire_begin;" // goto begin if failed store. - "li %0, 3;" // Set to 3 -> success in lock - "__cxa_guard_acquire_finish:" - : "+r" (c) : "r" (guard): "memory","cc" - ); - while (2 > c) - { - asm volatile("lwz %0, 0(%1);" : "=r" (c) : "r" (guard)); - } - return (3 == c ? 1 : 0); // 3 means success in lock, return 1 (obtained) - // 2 means initialized, return 0 -*/ } extern "C" void __cxa_guard_release(volatile uint64_t* gv) { + // Memory barrier to ensure all preceeding writes have completed before + // releasing guard. + lwsync(); + (*(volatile uint32_t*)gv) = 2; - /* - register volatile void* guard = gv; - register uint32_t c = 2; - asm volatile("stw %0, 0(%1)" :: "r"(c) , "r" (guard): "memory"); - */ return; } |
