Re: [PATCH 13/25] tests/tcg: fix constraints in test-i386-adcox

["Alex Bennée" <alex.bennee@linaro.org>]

Richard Henderson <richard.henderson@linaro.org> writes:

> On 2/26/25 06:03, Alex Bennée wrote:
>> Clang complains:
>>    clang -O2 -m64 -mcx16
>> /home/alex/lsrc/qemu.git/tests/tcg/i386/test-i386-adcox.c -o
>> test-i386-adcox -static
>>    /home/alex/lsrc/qemu.git/tests/tcg/i386/test-i386-adcox.c:32:26: error: invalid input constraint '0' in asm
>>            : "r" ((REG)-1), "0" (flags), "1" (out_adcx), "2" (out_adox));
>>                             ^
>>    /home/alex/lsrc/qemu.git/tests/tcg/i386/test-i386-adcox.c:57:26: error: invalid input constraint '0' in asm
>>            : "r" ((REG)-1), "0" (flags), "1" (out_adcx), "2" (out_adox));
>>                             ^
>>    2 errors generated.
>> Pointing out a numbered input constraint can't point to a read/write
>> output [1]. Convert to a read-only input constraint to allow this.
>> [1]
>> https://lists.llvm.org/pipermail/cfe-commits/Week-of-Mon-20101101/036036.html
>> Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
>> Suggested-by: Daniel P. Berrangé <berrange@redhat.com>
>> ---
>>   tests/tcg/i386/test-i386-adcox.c | 4 ++--
>>   1 file changed, 2 insertions(+), 2 deletions(-)
>> diff --git a/tests/tcg/i386/test-i386-adcox.c
>> b/tests/tcg/i386/test-i386-adcox.c
>> index 16169efff8..b56dbc00f2 100644
>> --- a/tests/tcg/i386/test-i386-adcox.c
>> +++ b/tests/tcg/i386/test-i386-adcox.c
>> @@ -28,7 +28,7 @@ void test_adox_adcx(uint32_t in_c, uint32_t in_o, REG adcx_operand, REG adox_ope
>>           "adox %3, %2;"
>>           "adcx %3, %1;"
>>           "pushf; pop %0"
>> -        : "+r" (flags), "+r" (out_adcx), "+r" (out_adox)
>> +        : "=r"(flags), "=r"(out_adcx), "=r"(out_adox)
>>           : "r" ((REG)-1), "0" (flags), "1" (out_adcx), "2" (out_adox));
>
> Alternately, drop all of the matching constraints as redundant.
> That's what "+r" does, anyway.

You mean like this:

    asm("push %0; popf;"
        "adox %3, %2;"
        "adcx %3, %1;"
        "pushf; pop %0"
        : "+r"(flags), "+r"(out_adcx), "+r"(out_adox));

Because that breaks the test:

  test-i386-adcox: /home/alex/lsrc/qemu.git/tests/tcg/i386/test-i386-adcox.c:33: test_adox_adcx: Assertion `out_adcx == in_c + adcx_operand - 1' failed.

>
>
> r~

-- 
Alex Bennée
Virtualisation Tech Lead @ Linaro