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> From: Hans-Peter Nilsson <h...@axis.com>
> Date: Thu, 5 Sep 2024 17:44:52 +0200
>
> Tested adding 0..more-than-four environment variables,
> running cris-sim+cris-elf. I also checked that foo stays
> the same generated code regardless of the new code: this is
> not obviously true as foo is "just" noinline, not __noipa__.
>
> Ok to commit?
>
> -- >8 --
> This test awkwardly "blinks"; xfails and xpasses apparently
> randomly for cris-elf using the "gdb simulator". On
> inspection, I see that the stack address depends on the
> number of environment variables, deliberately passed to the
> simulator, each adding the size of a pointer.
>
> This test is IMHO important enough not to be just skipped
> just because it blinks (fixing the actual problem is a
> different task).
>
> I guess a random non-16 stack-alignment could happen for
> other targets as well, so let's try and add a generic
> machinery to "stabilize" the test as failing, by allocating
> a dynamic amount to make sure it's misaligned. The most
> target-dependent item here is an offset between the incoming
> stack-pointer value (within main in the added framework) and
> outgoing (within "xmain" as called from main when setting up
> the p0 parameter). I know there are other wonderful stack
> shapes, but such targets would fall under the "complicated
> situations"-label and are no worse off than before.
>
> * gcc.dg/pr84877.c: Try to make the test result consistent by
> misaligning the stack.
> ---
> gcc/testsuite/gcc.dg/pr84877.c | 26 ++++++++++++++++++++++++++
> 1 file changed, 26 insertions(+)
>
> diff --git a/gcc/testsuite/gcc.dg/pr84877.c b/gcc/testsuite/gcc.dg/pr84877.c
> index e82991f42dd4..2f2e29578df9 100644
> --- a/gcc/testsuite/gcc.dg/pr84877.c
> +++ b/gcc/testsuite/gcc.dg/pr84877.c
> @@ -3,6 +3,32 @@
>
> #include <inttypes.h>
>
> +#ifdef __CRIS__
> +#define OUTGOING_SP_OFFSET (-sizeof (void *))
> +/* Suggestion: append #elif defined(__<TARGET-IDENTIFIER>__) after this
> comment,
> + either defining OUTGOING_SP_OFFSET to whatever the pertinent amount is at
> -O2,
> + if that makes your target consistently fail this test, or define
> + DO_NOT_TAMPER for more complicated situations. Either way, compile with
> + -DDO_NO_TAMPER to avoid any meddling. */
> +#endif
> +
> +#if defined (OUTGOING_SP_OFFSET) && !defined (DO_NOT_TAMPER)
> +extern int xmain () __attribute__ ((__noipa__));
> +int main ()
> +{
> + uintptr_t misalignment
> + = (OUTGOING_SP_OFFSET
> + + (15 & (uintptr_t) __builtin_stack_address ()));
> + /* Allocate a minimal amount if the stack was accidentally aligned. */
> + void *q = __builtin_alloca (misalignment == 0);
> + xmain ();
> + /* Fake use to avoid the "allocation" being optimized out. */
> + asm volatile ("" : : "rm" (q));
> + return 0;
> +}
> +#define main xmain
> +#endif
> +
> struct U {
> int M0;
> int M1;
> --
> 2.30.2
>
