[PATCH] Add ppc_ieee128_ok target-supports proc

[will schmidt]

Hi,
    
This adds a target_supports entry to check that the
_ieee128 keyword is understood by the target.
Also adds that require-effective-target check to the
existing pr92796 testcase.
    
Sniff tested on Linux (power6,power9) and AIX.
    
OK for master?

Thanks
-Will
    
[testsuite]
        * lib/target-supports.exp (check_effective_target_ppc_ieee128_ok): New.
        * gcc.target/powerpc/pr92796.c: Add
        require-effective-target ppc64_ieee128_ok.

diff --git a/gcc/testsuite/gcc.target/powerpc/pr92796.c 
b/gcc/testsuite/gcc.target/powerpc/pr92796.c
index aa15b2d..da4b6a4 100644
--- a/gcc/testsuite/gcc.target/powerpc/pr92796.c
+++ b/gcc/testsuite/gcc.target/powerpc/pr92796.c
@@ -1,7 +1,8 @@
 /* { dg-do compile } */
 /* { dg-options "-O2 -fstack-protector-strong -mcpu=power8" } */
+/* { dg-require-effective-target ppc_ieee128_ok } */
 
 typedef union
 {
   __ieee128 a;
   int b;
diff --git a/gcc/testsuite/lib/target-supports.exp 
b/gcc/testsuite/lib/target-supports.exp
index d3b2798..0154457 100644
--- a/gcc/testsuite/lib/target-supports.exp
+++ b/gcc/testsuite/lib/target-supports.exp
@@ -2248,10 +2248,32 @@ proc check_ppc_float128_hw_available { } {
            } $options
        }
     }]
 }
 
+# See if the __ieee128 keyword is understood.
+proc check_effective_target_ppc_ieee128_ok { } {
+    return [check_cached_effective_target ppc_ieee128_ok {
+       # disable on Darwin, AIX.
+       if { [istarget powerpc-*-eabi]
+            || [istarget powerpc*-*-eabispe]
+            || [istarget *-*-darwin*]
+            || [istarget *-*-aix*] } {
+           expr 0
+       } else {
+           set options "-mvsx"
+           check_runtime_nocache ppc_ieee128_ok {
+               int main()
+               {
+                 __ieee128 a;
+                 return 0;
+               }
+           } $options
+       }
+    }]
+}
+
 # Return 1 if the target supports executing VSX instructions, 0
 # otherwise.  Cache the result.
 
 proc check_vsx_hw_available { } {
     return [check_cached_effective_target vsx_hw_available {