The following testcase ICEs on x86_64 when asked to use the pre-GCC 8
ABI where zero sized arguments weren't ignored.
In GCC 7 the emit_push_insn calls in store_one_arg were unconditional,
it is true that they didn't actually push anything because it had zero
size, but because arg->locate.alignment_pad is 8 in this case,
emit_push_insn at the end performs
if (alignment_pad && args_addr == 0)
anti_adjust_stack (alignment_pad);
and an assert larger on is upset if we don't do it.
The following patch keeps the emit_push_insn conditional but calls
the anti_adjust_stack when needed by hand for the zero sized arguments.
For the new x86_64 ABI where zero sized arguments are ignored
arg->locate.alignment_pad is 0 in this case, so nothing changes
- we in that case really do ignore it.
There is another emit_push_insn call earlier in store_one_arg, also made
conditional on non-zero size by Marek in GCC 8, but that one is for
arguments with non-BLKmode and the only way those can be zero size is
if they are TYPE_EMPTY_P aka when they are completely ignored. But
I believe arg->locate.alignment_pad should be 0 in that case, so IMHO
there is no need to do anything in the second spot.
2022-03-03 Jakub Jelinek <jakub@redhat.com>
PR middle-end/104558
* calls.cc (store_one_arg): When not calling emit_push_insn
because size_rtx is const0_rtx, call at least anti_adjust_stack
on arg->locate.alignment_pad if !argblock and the alignment might
be non-zero.
* gcc.dg/pr104558.c: New test.
ARGS_SIZE_RTX (arg->locate.offset),
reg_parm_stack_space,
ARGS_SIZE_RTX (arg->locate.alignment_pad), false);
+ /* If we bypass emit_push_insn because it is a zero sized argument,
+ we still might need to adjust stack if such argument requires
+ extra alignment. See PR104558. */
+ else if ((arg->locate.alignment_pad.var
+ || maybe_ne (arg->locate.alignment_pad.constant, 0))
+ && !argblock)
+ anti_adjust_stack (ARGS_SIZE_RTX (arg->locate.alignment_pad));
/* Unless this is a partially-in-register argument, the argument is now
in the stack.
--- /dev/null
+/* PR middle-end/104558 */
+/* { dg-do compile } */
+/* { dg-options "-fabi-version=9" } */
+
+struct __attribute__ ((aligned)) A {};
+
+struct A a;
+
+void bar (int, int, int, int, int, int, int, struct A);
+
+void
+foo (void)
+{
+ bar (0, 1, 2, 3, 4, 5, 6, a);
+}