[PATCH,rs6000] Improve tests for Power9 vector shift variable instructions

[Kelvin Nilsen]

This patch improves upon a recently committed patch to change the
DejaGnu conditionals that control when the tests run.  The patch
corrects failures that occur on aix platforms.

This patch has bootstrapped on and regression tested on powerpc64le-
unknown-linux-gnu with no regressions.  Is this ok for trunk?  Is it ok
for gcc-6 after burn-in on the trunk?

Thanks.

gcc/testsuite/ChangeLog:

2016-06-28  Kelvin Nilsen  <kel...@gcc.gnu.org>

        * gcc.target/powerpc/vslv-0.c: Add a dg-require-effective-target
        directive to run this test only with compilers that are aware of
        Power9 instructions and add dg-skip-if directive to disable this
        test on aix platforms because of known incompatibilities.
        * gcc.target/powerpc/vslv-1.c: Likewise.
        * gcc.target/powerpc/vsrv-0.c: Likewise.
        * gcc.target/powerpc/vsrv-1.c: Likewise.

Index: gcc/testsuite/gcc.target/powerpc/vslv-0.c
===================================================================
--- gcc/testsuite/gcc.target/powerpc/vslv-0.c   (revision 237143)
+++ gcc/testsuite/gcc.target/powerpc/vslv-0.c   (working copy)
@@ -1,5 +1,7 @@
 /* { dg-do compile { target { powerpc*-*-* } } } */
 /* { dg-skip-if "do not override -mcpu" { powerpc*-*-* } { "-mcpu=*" } { 
"-mcpu=power9" } } */
+/* { dg-require-effective-target powerpc_p9vector_ok } */
+/* {dg-skip-if "" { powerpc*=*-aix* } } */
 /* { dg-options "-mcpu=power9" } */
 
 #include <altivec.h>
Index: gcc/testsuite/gcc.target/powerpc/vslv-1.c
===================================================================
--- gcc/testsuite/gcc.target/powerpc/vslv-1.c   (revision 237143)
+++ gcc/testsuite/gcc.target/powerpc/vslv-1.c   (working copy)
@@ -1,5 +1,7 @@
 /* { dg-do compile { target { powerpc*-*-* } } } */
 /* { dg-skip-if "do not override -mcpu" { powerpc*-*-* } { "-mcpu=*" } { 
"-mcpu=power9" } } */
+/* { dg-require-effective-target powerpc_p9vector_ok } */
+/* {dg-skip-if "" { powerpc*=*-aix* } } */
 /* { dg-options "-mcpu=power9" } */
 
 #include <altivec.h>
Index: gcc/testsuite/gcc.target/powerpc/vsrv-0.c
===================================================================
--- gcc/testsuite/gcc.target/powerpc/vsrv-0.c   (revision 237143)
+++ gcc/testsuite/gcc.target/powerpc/vsrv-0.c   (working copy)
@@ -1,5 +1,7 @@
 /* { dg-do compile { target { powerpc*-*-* } } } */
 /* { dg-skip-if "do not override -mcpu" { powerpc*-*-* } { "-mcpu=*" } { 
"-mcpu=power9" } } */
+/* { dg-require-effective-target powerpc_p9vector_ok } */
+/* {dg-skip-if "" { powerpc*=*-aix* } } */
 /* { dg-options "-mcpu=power9" } */
 
 #include <altivec.h>
Index: gcc/testsuite/gcc.target/powerpc/vsrv-1.c
===================================================================
--- gcc/testsuite/gcc.target/powerpc/vsrv-1.c   (revision 237143)
+++ gcc/testsuite/gcc.target/powerpc/vsrv-1.c   (working copy)
@@ -1,5 +1,7 @@
 /* { dg-do compile { target { powerpc*-*-* } } } */
 /* { dg-skip-if "do not override -mcpu" { powerpc*-*-* } { "-mcpu=*" } { 
"-mcpu=power9" } } */
+/* { dg-require-effective-target powerpc_p9vector_ok } */
+/* {dg-skip-if "" { powerpc*=*-aix* } } */
 /* { dg-options "-mcpu=power9" } */
 
 #include <altivec.h>