+#ifdef __x86_64__
+/* See GLIBC for additional information about this technique. */
+asm(".globl _mcount\n"
+ "\t.type\t_mcount, @function\n"
+ "_mcount:\n"
+ /* The compiler calls _mcount after the prologue, and does not
+ save any of the registers. Therefore we must preserve all
+ seven registers which may contain function arguments. */
+ "\tsubq\t$0x38,%rsp\n"
+ "\tmovq\t%rax,(%rsp)\n"
+ "\tmovq\t%rcx,0x08(%rsp)\n"
+ "\tmovq\t%rdx,0x10(%rsp)\n"
+ "\tmovq\t%rsi,0x18(%rsp)\n"
+ "\tmovq\t%rdi,0x20(%rsp)\n"
+ "\tmovq\t%r8,0x28(%rsp)\n"
+ "\tmovq\t%r9,0x30(%rsp)\n"
+ /* Get SELFPC (pushed by the call to this function) and
+ FROMPCINDEX (via the frame pointer. */
+ "\tmovq\t0x38(%rsp),%rdi\n"
+ "\tmovq\t0x8(%rbp),%rsi\n"
+ "\tcall\tinternal_mcount\n"
+ /* Restore the saved registers. */
+ "\tmovq\t0x30(%rsp),%r9\n"
+ "\tmovq\t0x28(%rsp),%r8\n"
+ "\tmovq\t0x20(%rsp),%rdi\n"
+ "\tmovq\t0x18(%rsp),%rsi\n"
+ "\tmovq\t0x10(%rsp),%rdx\n"
+ "\tmovq\t0x08(%rsp),%rdx\n"
+ "\tmovq\t(%rsp),%rax\n"
+ "\taddq\t$0x38,%rsp\n"
+ "\tretq\n"
+ );
+#else