On Mon, Mar 12, 2018 at 4:18 AM, H.J. Lu <hjl.to...@gmail.com> wrote:
> On Thu, Mar 8, 2018 at 10:19 AM, Jakub Jelinek <ja...@redhat.com> wrote:
>> Hi!
>>
>> We have many loops that use CONSTRAINT_LEN to skip over various constraint
>> characters, but we assume the constraints have valid length and don't walk
>> the individual characters to double check this.
>>
>> If that is not the case, when e.g. 2 character constraint starting letter
>> is followed by '\0', we'd reject it early (during vregs pass, through
>> asm_operand_ok). The PR has different testcase (that fails randomly based
>> on ASLR), where a 2 character constraint starting letter is followed by ',',
>> and several spots expect that not to happen (they count number of
>> alternatives and then for each alternative walk with skipping CONSTRAINT_LEN
>> characters).
>>
>> This patch diagnoses this problematic case early as well.
>>
>> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
>>
>> 2018-03-08 Jakub Jelinek <ja...@redhat.com>
>>
>> PR inline-asm/84742
>> * recog.c (asm_operand_ok): Return 0 if multi-character constraint
>> has ',' character inside of it.
>>
>> * gcc.target/i386/pr84742-1.c: New test.
>> * gcc.target/i386/pr84742-2.c: New test.
>>
>> --- gcc/recog.c.jj 2018-01-16 09:53:47.000000000 +0100
>> +++ gcc/recog.c 2018-03-08 14:04:35.889274871 +0100
>> @@ -1825,7 +1825,7 @@ asm_operand_ok (rtx op, const char *cons
>> len = CONSTRAINT_LEN (c, constraint);
>> do
>> constraint++;
>> - while (--len && *constraint);
>> + while (--len && *constraint && *constraint != ',');
>> if (len)
>> return 0;
>> }
>> --- gcc/testsuite/gcc.target/i386/pr84742-1.c.jj 2018-03-08
>> 14:11:20.155463943 +0100
>> +++ gcc/testsuite/gcc.target/i386/pr84742-1.c 2018-03-08
>> 14:12:28.453495882 +0100
>> @@ -0,0 +1,10 @@
>> +/* PR inline-asm/84742 */
>> +/* { dg-do compile } */
>> +/* { dg-options "-O2" } */
>> +
>> +void
>> +foo ()
>> +{
>> + char b = 1;
>> + asm volatile ("" : "+T,Y" (b)); /* { dg-error "impossible constraint
>> in 'asm'" } */
>> +}
>
> This test fails at random on 32-bit hosts (i686 and x32). Sometimes I got
>
> spawn -ignore SIGHUP
> /export/build/gnu/gcc-32bit-all-test/build-i686-linux/gcc/xgcc
> -B/export/build/gnu/gcc-32bit-all-test/build-i686-linux/gcc/
> /export/gnu/import/git/sources/gcc/gcc/testsuite/gcc.target/i386/pr84742-1.c
> -m32 -fno-diagnostics-show-caret -fdiagnostics-color=never -O2 -S -o
> pr84742-1.s
> /export/gnu/import/git/sources/gcc/gcc/testsuite/gcc.target/i386/pr84742-1.c:
> In function 'foo':
> /export/gnu/import/git/sources/gcc/gcc/testsuite/gcc.target/i386/pr84742-1.c:9:3:
> error: matching constraint not valid in output operand
> /export/gnu/import/git/sources/gcc/gcc/testsuite/gcc.target/i386/pr84742-1.c:9:3:
> error: matching constraint not valid in output operand
> FAIL: gcc.target/i386/pr84742-1.c (test for errors, line 9)
> FAIL: gcc.target/i386/pr84742-1.c (test for excess errors)
>
> But when I ran it by hand:
>
> [hjl@gnu-skx-1 gcc]$
> /export/build/gnu/gcc-32bit-all-test/build-i686-linux/gcc/xgcc
> -B/export/build/gnu/gcc-32bit-all-test/build-i686-linux/gcc/
> /export/gnu/import/git/sources/gcc/gcc/testsuite/gcc.target/i386/pr84742-1.c
> -m32 -fno-diagnostics-show-caret -fdiagnostics-color=never -O2 -S -o
> pr84742-1.s
> /export/gnu/import/git/sources/gcc/gcc/testsuite/gcc.target/i386/pr84742-1.c:
> In function \u2018foo\u2019:
> /export/gnu/import/git/sources/gcc/gcc/testsuite/gcc.target/i386/pr84742-1.c:9:3:
> error: impossible constraint in \u2018asm\u2019
> [hjl@gnu-skx-1 gcc]$
>
>
I opened;
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84831
--
H.J.
