There is the following code in aarch64_layout_frame: else if (crtl->outgoing_args_size.is_constant (&const_outgoing_args_size) && frame.saved_regs_size.is_constant (&const_saved_regs_size) && const_outgoing_args_size + const_saved_regs_size < 512 && (!saves_below_hard_fp_p || const_outgoing_args_size == 0) // 1) && !(cfun->calls_alloca && frame.hard_fp_offset.is_constant (&const_fp_offset) && const_fp_offset < max_push_offset)) { /* Frame with small outgoing arguments:
sub sp, sp, frame_size stp reg1, reg2, [sp, outgoing_args_size] stp reg3, reg4, [sp, outgoing_args_size + 16] */ frame.initial_adjust = frame.frame_size; frame.callee_offset = const_outgoing_args_size; } ...... else if (frame.hard_fp_offset.is_constant (&const_fp_offset) && const_fp_offset < max_push_offset) { // 2) /* Frame with large outgoing arguments or SVE saves, but with a small local area: stp reg1, reg2, [sp, -hard_fp_offset]! stp reg3, reg4, [sp, 16] [sub sp, sp, below_hard_fp_saved_regs_size] [save SVE registers relative to SP] sub sp, sp, outgoing_args_size */ As described in 2), "Frame with large outgoing arguments or SVE saves, but with a small local area". But due to the condition at 1), the following code (small outgoing with a small local area) also uses the insns in 2), which is slightly different from the description: //aarch64-linux-gnu-gcc main.c -O0 -S main.s -g -w -fomit-frame-pointer #include <stdio.h> #include <alloca.h> #define REP9(X) X,X,X,X,X,X,X,X,X int alloc_size; int main(void) { outgoing (REP9(1)); char * y = alloca(alloc_size); return 0; } Could the condition in 1) be removed, or am I missing something? Thanks, Dan.