rs6000: Consider explicit VSX when masking off ALTIVEC [PR115688]

PR115688 exposes an inconsistent state in which we have VSX
enabled but ALTIVEC disabled.  There is one hunk:

  if (main_target_opt && !main_target_opt->x_rs6000_altivec_abi)
    rs6000_isa_flags &= ~((OPTION_MASK_VSX | OPTION_MASK_ALTIVEC)
			  & ~rs6000_isa_flags_explicit);

which disables both VSX and ALTIVEC together only considering
them explicitly set or not.  For the given case, VSX is explicitly
specified, altivec is implicitly enabled as it's part of set
ISA_2_6_MASKS_SERVER.  When falling into the above hunk, vsx is
kept as it's explicitly enabled but altivec gets masked off, it's
unexpected.

This patch is to consider explicit VSX when masking off ALTIVEC,
not mask off it if TARGET_VSX and it's explicitly set.

	PR target/115688

gcc/ChangeLog:

	* config/rs6000/rs6000.cc (rs6000_option_override_internal): Consider
	explicit VSX when masking off ALTIVEC.

gcc/testsuite/ChangeLog:

	* gcc.target/powerpc/pr115688.c: New test.

2 files changed, 20 insertions, 2 deletions

diff --git a/gcc/config/rs6000/rs6000.cc b/gcc/config/rs6000/rs6000.cc
index 58553ff..2cbea6e 100644
--- a/gcc/config/rs6000/rs6000.cc
+++ b/gcc/config/rs6000/rs6000.cc
@@ -3933,8 +3933,12 @@ rs6000_option_override_internal (bool global_init_p)
      not for 32-bit.  Don't move this before the above code using ignore_masks,
      since it can reset the cleared VSX/ALTIVEC flag again.  */
   if (main_target_opt && !main_target_opt->x_rs6000_altivec_abi)
-    rs6000_isa_flags &= ~((OPTION_MASK_VSX | OPTION_MASK_ALTIVEC)
-			  & ~rs6000_isa_flags_explicit);
+    {
+      rs6000_isa_flags &= ~(OPTION_MASK_VSX & ~rs6000_isa_flags_explicit);
+      /* Don't mask off ALTIVEC if it is enabled by an explicit VSX.  */
+      if (!TARGET_VSX)
+	rs6000_isa_flags &= ~(OPTION_MASK_ALTIVEC & ~rs6000_isa_flags_explicit);
+    }
 
   if (TARGET_CRYPTO && !TARGET_ALTIVEC)
     {
diff --git a/gcc/testsuite/gcc.target/powerpc/pr115688.c b/gcc/testsuite/gcc.target/powerpc/pr115688.c
new file mode 100644
index 0000000..5222e66
--- /dev/null
+++ b/gcc/testsuite/gcc.target/powerpc/pr115688.c
@@ -0,0 +1,14 @@
+/* { dg-do compile { target powerpc*-*-linux* } } */
+/* { dg-options "-mdejagnu-cpu=power5 -O2" } */
+
+/* Ignore some error messages on "target attribute or
+   pragma changes AltiVec ABI".  */
+/* { dg-excess-errors "pr115688" { target ilp32 } } */
+
+/* Verify there is no ICE under 32 bit env.  */
+
+__attribute__((target("vsx")))
+int test (void)
+{
+  return 0;
+}