[PATCH] Adjust testcase for O2 vectorization.

[Martin Sebor]

On 10/14/21 1:11 AM, liuhongt wrote:
> Hi Kewen:
>    Cound you help to verify if this patch fix those regressions
> for rs6000 port.
> 
> As discussed in [1], this patch add xfail/target selector to those
> testcases, also make a copy of them so that they can be tested w/o
> vectorization.

Just to make sure I understand what's happening with the tests:
the new -N-novec.c tests consist of just the casses xfailed due
to vectorizartion in the corresponding -N.c tests?  Or are there
some other differences (e.g., new cases in them, etc.)?  I'd
hope to eventually remove the -novec.c tests once all warnings
behave as expected with vectorization as without it (maybe
keeping just one case both ways as a sanity check).

For the target-supports selectors, I confess I don't know enough
about vectorization to find their names quite intuitive enough
to know when to use each.  For instance, for vect_slp_v4qi_store:

+# Return the true if target support vectorization of v4qi store.
+proc check_effective_target_vect_slp_v4qi_store { } {
+    set pattern {add new stmt: MEM <vector\(4\) char>}
+    return [expr { [check_vect_slp_vnqihi_store_usage $pattern ] != 0 }]
+}

When should this selector be used?  In cases involving 4-byte
char stores?  Only naturally aligned 4-bytes stores (i.e., on
a 4 byte boundary, as the check_vect_slp_vnqihi_store_usage
suggests?) Or 4-byte stores of any types (e.g., four chars
as well as two 16-bit shorts), etc.?

Hopefully once all the warnings handle vectorization we won't
need to use them, but until then it would be good to document
this in more detail in the .exp file.

Finally, thank you for adding comments to the xfailed tests
referencing the corresponding bugs!  Can you please mention
the PR in the comment in each of the new xfails?  Like so:

index 7d29b5f48c7..cb687c69324 100644
--- a/gcc/testsuite/c-c++-common/Wstringop-overflow-2.c
+++ b/gcc/testsuite/c-c++-common/Wstringop-overflow-2.c
@@ -189,8 +189,9 @@ void ga1__ (void)

    struct A1 a = { 1 };
    a.a[0] = 0;
+  // O2 vectorization regress Wstringop-overflow case (1), refer to 
pr102462.
    a.a[1] = 1;                    // { dg-warning 
"\\\[-Wstringop-overflow" }
-  a.a[2] = 2;                    // { dg-warning 
"\\\[-Wstringop-overflow" "" { xfail { i?86-*-* x86_64-*-* } } }
+  a.a[2] = 2;                    // { dg-warning 
"\\\[-Wstringop-overflow" "pr102462" { xfail { vect_slp_v2qi_store } } }
            ^^^^^^^^
            PR in dg-warning comment.

This should make it easier to deal with the XFAILs once
the warnings have improved to handle vectorization.

Martin