Re: [PATCH] fix pdp11_expand_epilogue (PR target/107841)

[Paul Koning <paulkoning@comcast.net>]

> On Jul 13, 2023, at 12:47 PM, Mikael Pettersson <mikpelinux@gmail.com> wrote:
> 
> If the stack frame only contains an alloca area, then
> pdp11_expand_epilogue fails to deallocate it, resulting
> in callee-saved registers and the return address being
> restored from the wrong stack slots.  Fixed by adding
> || cfun->calls_alloca to the condition for deallocating
> the frame.
> 
> Tested with a cross to pdp11-unknown-aout.
> 
> Ok for master? (Note: I don't have commit rights.)
> 
> gcc/
> 
> 	PR target/107841
> 	* config/pdp11/pdp11.c (pdp11_expand_epilogue): Also
> 	deallocate alloca-only frame.
> 
> gcc/testsuite/
> 
> 	PR target/107841
> 	* gcc.target/pdp11/pr107841.c: New test.
> ---
> gcc/config/pdp11/pdp11.cc                 |  2 +-
> gcc/testsuite/gcc.target/pdp11/pr107841.c | 12 ++++++++++++
> 2 files changed, 13 insertions(+), 1 deletion(-)
> create mode 100644 gcc/testsuite/gcc.target/pdp11/pr107841.c
> 
> diff --git a/gcc/config/pdp11/pdp11.cc b/gcc/config/pdp11/pdp11.cc
> index f6dd841f184..311a1d225e0 100644
> --- a/gcc/config/pdp11/pdp11.cc
> +++ b/gcc/config/pdp11/pdp11.cc
> @@ -393,7 +393,7 @@ pdp11_expand_epilogue (void)
>   rtx x, reg, via_ac = NULL;
> 
>   /* Deallocate the local variables.  */
> -  if (fsize)
> +  if (fsize || cfun->calls_alloca)
>     {
>       if (frame_pointer_needed)
> 	{
> diff --git a/gcc/testsuite/gcc.target/pdp11/pr107841.c b/gcc/testsuite/gcc.target/pdp11/pr107841.c
> new file mode 100644
> index 00000000000..a363c468b0b
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/pdp11/pr107841.c
> @@ -0,0 +1,12 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2" } */
> +
> +/* Verify that the stack frame is deallocated using the frame pointer.  */
> +
> +void qq (int a)
> +{
> +    char *s = __builtin_alloca (128);
> +    __builtin_sprintf (s, "qq %d", 3);
> +}
> +
> +/* { dg-final { scan-assembler "mov\tr5,sp" } } */
> -- 
> 2.41.0
> 


Thanks Mikael.  I committed this fix.

	paul