On Fri, Mar 13, 2015 at 03:54:57PM -0600, Martin Sebor wrote:
> Attached is a patch that eliminates the unused stack frame
> allocated by gcc 5 with -pg -mprofile-kernel on powepc64le
> and brings the code into parity with previous gcc versions.
>
> The patch doesn't do anything to change the emitted code
> when -mprofile-kernel is used without -pg. Since the former
> option isn't fully documented (as noted in pr 65372) it's
> unclear what effect it should be expected to have without
> -pg.
-mprofile-kernel does nothing without profiling enabled. Maybe it
should just have been called -pk or something horrid like that.
The effect it should have is to do what the only user of the option
(the 64-bit PowerPC Linux kernel) wants. The effect it does have
is to make the 64-bit ABI more like the 32-bit ABI for mcount.
> 2015-03-13 Anton Blanchard <an...@samba.org>
>
> PR target/63354
> * gcc/config/rs6000/linux64.h (ARGET_KEEP_LEAF_WHEN_PROFILED): Define.
^ typo
> * cc/config/rs6000/rs6000.c (rs6000_keep_leaf_when_profiled). New
^ typo ^ typo
It shouldn't have "gcc/" in the path names at all, actually.
> +/* -mprofile-kernel code calls mcount before the function prolog,
"prologue".
> + so a profiled leaf function should stay a leaf function. */
> +
> +static bool
> +rs6000_keep_leaf_when_profiled (void)
> +{
> + return TARGET_PROFILE_KERNEL;
> +}
Something like
switch (DEFAULT_ABI)
{
case ABI_AIX:
case ABI_ELFv2:
return TARGET_PROFILE_KERNEL;
default:
return true;
}
although I'm not sure about Darwin here. More conservative is to
return false for anything untested, of course.
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/powerpc/pr63354.c
> @@ -0,0 +1,10 @@
> +/* { dg-do compile { target { powerpc*-*-* } } } */
> +/* { dg-options "-O2 -pg -mprofile-kernel" } */
> +
> +int foo (void)
> +{
> + return 1;
> +}
> +
> +/* { dg-final { scan-assembler "bl _mcount" } } */
> +/* { dg-final { scan-assembler-not "\(addi|stdu\) 1," } } */
Either you should run this only on AIX/ELFv2 ABIs, or you want to
test for "stwu" as well. Bare "1" does not work for all assemblers
(only Darwin again?)
Segher
