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

[Tom de Vries <tdevries@suse.de>]

On 11/28/22 18:02, Carl Love wrote:
> 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.

Hi Carl,

thanks for confirming, good to know.

- Tom