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      1 /* ===----- trampoline_setup.c - Implement __trampoline_setup -------------===
      2  *
      3  *                     The LLVM Compiler Infrastructure
      4  *
      5  * This file is dual licensed under the MIT and the University of Illinois Open
      6  * Source Licenses. See LICENSE.TXT for details.
      7  *
      8  * ===----------------------------------------------------------------------===
      9  */
     10 
     11 #include "int_lib.h"
     12 
     13 extern void __clear_cache(void* start, void* end);
     14 
     15 /*
     16  * The ppc compiler generates calls to __trampoline_setup() when creating
     17  * trampoline functions on the stack for use with nested functions.
     18  * This function creates a custom 40-byte trampoline function on the stack
     19  * which loads r11 with a pointer to the outer function's locals
     20  * and then jumps to the target nested function.
     21  */
     22 
     23 #if __ppc__ && !defined(__powerpc64__)
     24 COMPILER_RT_ABI void
     25 __trampoline_setup(uint32_t* trampOnStack, int trampSizeAllocated,
     26                    const void* realFunc, void* localsPtr)
     27 {
     28     /* should never happen, but if compiler did not allocate */
     29     /* enough space on stack for the trampoline, abort */
     30     if ( trampSizeAllocated < 40 )
     31         compilerrt_abort();
     32 
     33     /* create trampoline */
     34     trampOnStack[0] = 0x7c0802a6;    /* mflr r0 */
     35     trampOnStack[1] = 0x4800000d;    /* bl Lbase */
     36     trampOnStack[2] = (uint32_t)realFunc;
     37     trampOnStack[3] = (uint32_t)localsPtr;
     38     trampOnStack[4] = 0x7d6802a6;    /* Lbase: mflr r11 */
     39     trampOnStack[5] = 0x818b0000;    /* lwz    r12,0(r11) */
     40     trampOnStack[6] = 0x7c0803a6;    /* mtlr r0 */
     41     trampOnStack[7] = 0x7d8903a6;    /* mtctr r12 */
     42     trampOnStack[8] = 0x816b0004;    /* lwz    r11,4(r11) */
     43     trampOnStack[9] = 0x4e800420;    /* bctr */
     44 
     45     /* clear instruction cache */
     46     __clear_cache(trampOnStack, &trampOnStack[10]);
     47 }
     48 #endif /* __ppc__ && !defined(__powerpc64__) */
     49