Ok this test is checking a corner case of the language, namely
non power of two modular types.
It looks like this one needs overflow checking to pass (-gnato):
$ gnatmake -f -I../../../support/ c460008.adb
gcc -c -I../../../support/ c460008.adb
gcc -c -I./ -I../../../support/ -I-
/home/guerby/work/gcc/build/build-head-20060301T130355/gcc/testsuite/ada/acats/support/report.adb
gnatbind -aO./ -I../../../support/ -I- -x c460008.ali
gnatlink c460008.ali
$ ./c460008
,.,. C460008 ACATS 2.5 06-03-02 00:28:43
---- C460008 Check that conversion to a modular type raises
Constraint_Error when the operand value is outside the
base range of the modular type.
* C460008 Fix expected Constraint_Error D2S Dynamic, Negative.
- C460008 Value of 251 not properly converted.
* C460008 Fix expected Constraint_Error D2S Static, Over_Mod.
- C460008 Value of 204 not properly converted.
* C460008 Fix expected Constraint_Error D28 Static, Negative.
- C460008 Value of 255 not properly converted.
* C460008 Fix expected Constraint_Error D28 Static, At_Mod.
- C460008 Value of 0 not properly converted.
* C460008 Fix expected Constraint_Error D28 Dynamic, Over_Mod.
- C460008 Value of 209 not properly converted.
**** C460008 FAILED ****************************.
$ gnatmake -f -gnato -I../../../support/ c460008.adb
gcc -c -gnato -I../../../support/ c460008.adb
gcc -c -I./ -gnato -I../../../support/ -I-
/home/guerby/work/gcc/build/build-head-20060301T130355/gcc/testsuite/ada/acats/support/report.adb
gnatbind -aO./ -I../../../support/ -I- -x c460008.ali
gnatlink c460008.ali
$ ./c460008
,.,. C460008 ACATS 2.5 06-03-02 00:27:21
---- C460008 Check that conversion to a modular type raises
Constraint_Error when the operand value is outside the
base range of the modular type.
==== C460008 PASSED ============================.
I'm rerunning the whole testsuite on x86_64-linux with an edited
gcc/testsuite/ada/acats/run_all.sh that includes -gnato for all tests:
gnatflags="-gnatws -gnato"
We'll see what new ACATS FAIL go away.
Richard, Arnaud, could you check amongst GNAT experts if for such types
(non power of two modulus), it's not worth enabling overflow checks by
default now that we have VRP doing non trivial optimisations? People
using non power of two modulus are not caring for performance anyway, so
having a compliant implementation by default won't harm.
Laurent
On Wed, 2006-03-01 at 15:35 -0700, Jeffrey A Law wrote:
> Here's the next segment in the ongoing saga of VRP vs Ada...
> Not surprisingly we have another case where an object gets a
> value outside of its TYPE_MIN_VALUE/TYPE_MAX_VALUE defined range.
>
> Investigating the c460008 testsuite failure we have the following
> code for Fixed_To_Short before VRP runs:
>
>
>
>
> # BLOCK 4
> # PRED: 3 (fallthru,exec)
> D.1294_13 = D.1294_12;
> D.1309_32 = for_the_value_31 /[rd] 1000000000;
> D.1310_33 = (UNSIGNED_64) D.1309_32;
> if (D.1310_33 > 255) goto <L0>; else goto <L1>;
> # SUCC: 5 (true,exec) 6 (false,exec)
>
> # BLOCK 5
> # PRED: 4 (true,exec)
> <L0>:;
> __gnat_rcheck_10 ("c460008.adb", 162);
> # SUCC: 13 (ab,eh,exec) 18 (ab,eh,exec) 29 (ab,eh,exec)
>
> # BLOCK 6
> # PRED: 4 (false,exec)
> <L1>:;
> iftmp.78_63 = D.1309_32;
> iftmp.78_64 = D.1309_32;
> D.1316_65 = (c460008__unsigned_edge_8) D.1309_32;
> if (D.1316_65 == 255) goto <L3>; else goto <L4>;
> # SUCC: 7 (true,exec) 8 (false,exec)
>
> D.1309_32's type has the range [0x8000000000000000,0x7fffffffffffffff]
> with 64bit precision.
>
> In block #6 we cast the value of D.1309_32 into a smaller type,
> specifically c460008__unsigned_edge_8 and store the result into
> D.1316_64 which has type c460008__unsigned_edge_8.
>
> c460008__unsigned_edge_8's range is [ ,254] with 8 bit precision.
>
> Note carefully that with the range [ ,254] (according to
> TYPE_MIN_VALUE/TYPE_MAX_VALUE) that the test
>
> if (D.1316_65 == 255)
>
> Must always be false. So VRP, as expected, wipes out test
> completely.
>
> The problem (of course) is D.1316_65 can and does actually hold
> values outside the range [ ,254] at runtime. For example, it could
> hold the value 255 if D.1309_32 had the value 255, which would occur
> if for_the_value_31 held the value 255000000000.
>
> Someone with a better knowledge of Ada is going to need to step
> in here, but based on the type information provided by the Ada
> front-end, VRP is doing the right thing here.
>
>
> Jeff
>
>
