https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85669
--- Comment #44 from Douglas Mencken <dougmencken at gmail dot com> --- I got assembly of pr78468.c from various versions of GCC • 7.3 produces absolutely the same as patched 8.2 • 6.4 produces slightly different assembly with stmw & lmw and different sequence of instructions, but numbers like in “addi r2,r1,103” are the same • 4.2.1 can’t compile it at all pr78468.c:9: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or ‘__attribute__’ before ‘uintptr_t’ (In reply to Wilco from comment #43) > No the problem is not in this code. It's STACK_DYNAMIC_OFFSET which is wrong. I can’t get where is the value of STACK_DYNAMIC_OFFSET in published assembly and why do you think it is wrong It seems that the problem is in fact that your version of get_dynamic_stack_size from explow.c (introduced with r251713) gives out too small values, for example in _t1_a8 it is fifteen “addi r3,r3,15” while ages before that it worked as being “addi r3,r3,22” - addi r3,r3,15 + addi r3,r3,22 And aligning looks okay, it is then handled by code for #define RS6000_ALIGN(n,a) ROUND_UP ((n), (a)) #define ROUND_UP(x,y) (((x) + (y) - 1) & ~((y) - 1)) part of which is rlwinm and such (16 + 15) & ~15 = 16 (16 + 22) & ~15 = 32 Thus for your version of get_dynamic_stack_size that size is 16 here, but for previous ones it is 32. And eventually this leads to fail for such built-ins as acos, floor, &c.
