Re: [pushed] [gdb/testsuite] Fix gdb.arch/altivec-regs.exp with gcc 4.8.5

[Carl Love <cel@us.ibm.com>]

Tom:

On Mon, 2022-11-28 at 13:57 +0100, Tom de Vries wrote:
> On powerpc64le-linux, using gcc 4.8.5, I run into:
> ...
> (gdb) PASS: gdb.arch/altivec-regs.exp: next (1)
> next^M
> 11        c = vec_add (a, b);^M
> (gdb) PASS: gdb.arch/altivec-regs.exp: next (2)
> print/x a^M
> $67 = {0xfefefefe, 0xfefefefe, 0xfefefefe, 0xfefefefe}^M
> (gdb) FAIL: gdb.arch/altivec-regs.exp: print vector parameter a
> ...
> 
> Looking at the disassembly and the debug info, it's clear why there's
> a FAIL.
> 
> The debug info says that the variable can be found at some stack
> location, but
> the instructions don't seem to be writing there.
> 
> We can work around this by marking variable a volatile.  Likewise for
> b.
> 
> Note that marking the variables as volatile doesn't change the
> location
> information.
> 
> Tested on power64le-linux.
> ---
>  gdb/testsuite/gdb.arch/altivec-regs.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/gdb/testsuite/gdb.arch/altivec-regs.c
> b/gdb/testsuite/gdb.arch/altivec-regs.c
> index 4d4fe3f5dbb..8f3b729fe3f 100644
> --- a/gdb/testsuite/gdb.arch/altivec-regs.c
> +++ b/gdb/testsuite/gdb.arch/altivec-regs.c
> @@ -2,7 +2,7 @@
>  #include <stdio.h>
> 
>  vector unsigned int
> -vector_fun (vector unsigned int a, vector unsigned int b)
> +vector_fun (volatile vector unsigned int a, volatile vector unsigned
> int b)
>  {
>    vector unsigned int c;
>    a = ((vector unsigned int) vec_splat_u8(2));
> 
> base-commit: 2650ea9730e31fc5c9111afc1a689dbca76707f5

I ran this test case before and after your commit on my Power 10 and my
Power 9 box.  I did not see a failure before or after the commit on
either machine.  The fix looks fine to me as it doesn't change the
behavior on Power 9 or Power 10 that I can see.

                    Carl