[PATCH] testsuite: add -fno-tree-fre in gcc.dg/guality

[Richard Biener]

On Thu, Aug 27, 2020 at 3:38 AM Hu Jiangping <hujiangping@cn.fujitsu.com> wrote:
>
> This patch add -fno-tree-fre to dg-options in gcc.dg/guality/sra-1.c,
> to make the following testcases passed.
>
> FAIL: gcc.dg/guality/sra-1.c  -Og -DPREVENT_OPTIMIZATION  line 43 a.i == 4
> FAIL: gcc.dg/guality/sra-1.c  -Og -DPREVENT_OPTIMIZATION  line 43 a.j == 14
> FAIL: gcc.dg/guality/sra-1.c   -O2 -flto -fuse-linker-plugin -fno-fat-lto-objects -DPREVENT_OPTIMIZATION line 21 a.j == 14
> FAIL: gcc.dg/guality/sra-1.c   -O2 -flto -fuse-linker-plugin -fno-fat-lto-objects -DPREVENT_OPTIMIZATION line 32 a[1] == 14
> FAIL: gcc.dg/guality/sra-1.c   -O2 -flto -fuse-linker-plugin -fno-fat-lto-objects -DPREVENT_OPTIMIZATION line 43 a.j == 14
>
> The detail error logs like this:
> > Spawning: gdb -nx -nw -quiet -batch -x sra-1.gdb ./sra-1.exe
> > spawn gdb -nx -nw -quiet -batch -x sra-1.gdb ./sra-1.exe
> > Breakpoint 1 at 0x40074c: file /home/build_gcc/gcc-a64fx-1-a/gcc/testsuite/gcc.dg/guality/sra-1.c, line 43.
> >
> > Breakpoint 1, f3 (k=k@entry=7) at /home/build_gcc/gcc-a64fx-1-a/gcc/testsuite/gcc.dg/guality/sra-1.c:43
> > 43        bar (a.j);            /* { dg-final { gdb-test . "a.j" "14" } } */
> > $1 = <optimized out>
> > $2 = 4
> > <optimized out> != 4
>
> Tested on aarch64.

Huh well - I guess it should be XFAILed instead?  But then we see
XPASSes.  Disabling
FRE doesn't look correct - we _do_ want the test to succeed here.  Did
you analyze
why it fails?

It looks like we assign 'a' a register at RTL expansion time for -Og
but do not perform any
fancy tracking of components of it then.  On GIMPLE we assume it's eventually
memory and thus wouldn't bother with any debug stmts.

So it's a genuine FAIL for -Og at least.  That said, the logic is simple - both
a.i and a.j need to be available for a.i + a.j to be evaluated.  For
some reasons
we fail to record where their value resides.  For -Og they are in
%rbp, resp. %rbx.
But obviously some elaborate DWARF is necessary to convey that info.

Richard.

> Regards!
> hujp
>
> ---
>  gcc/testsuite/gcc.dg/guality/sra-1.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/gcc/testsuite/gcc.dg/guality/sra-1.c b/gcc/testsuite/gcc.dg/guality/sra-1.c
> index 8ad57cf3f8e..94ea29dd727 100644
> --- a/gcc/testsuite/gcc.dg/guality/sra-1.c
> +++ b/gcc/testsuite/gcc.dg/guality/sra-1.c
> @@ -1,6 +1,6 @@
>  /* PR debug/43983 */
>  /* { dg-do run } */
> -/* { dg-options "-g -fno-ipa-icf" } */
> +/* { dg-options "-g -fno-tree-fre -fno-ipa-icf" } */
>
>  struct A { int i; int j; };
>  struct B { int : 4; int i : 12; int j : 12; int : 4; };
> --
> 2.17.1
>
>
>