[gcc r15-703] rs6000: Add assert !TARGET_VSX if !TARGET_ALTIVEC and strip a useless check

[gcc r15-703] rs6000: Add assert !TARGET_VSX if !TARGET_ALTIVEC and strip a useless check

[Kewen Lin]

https://gcc.gnu.org/g:b390b0115696353ba579706531fbd3bcf39281c5

commit r15-703-gb390b0115696353ba579706531fbd3bcf39281c5
Author: Kewen Lin <linkw@linux.ibm.com>
Date:   Mon May 20 21:01:06 2024 -0500

    rs6000: Add assert !TARGET_VSX if !TARGET_ALTIVEC and strip a useless check
    
    In function rs6000_option_override_internal, we have the
    checks and adjustments like:
    
      if (TARGET_P8_VECTOR && !TARGET_ALTIVEC)
        rs6000_isa_flags &= ~OPTION_MASK_P8_VECTOR;
    
      if (TARGET_P8_VECTOR && !TARGET_VSX)
        rs6000_isa_flags &= ~OPTION_MASK_P8_VECTOR;
    
    But in fact some previous code has guaranteed !TARGET_VSX if
    !TARGET_ALTIVEC, so we can remove the former check and
    adjustment.  This patch is to remove it accordingly and also
    place an explicit assertion.
    
    gcc/ChangeLog:
    
            * config/rs6000/rs6000.cc (rs6000_option_override_internal): Remove
            useless check on TARGET_P8_VECTOR && !TARGET_ALTIVEC and add an
            assertion on !TARGET_VSX if !TARGET_ALTIVEC.

Diff:
---
 gcc/config/rs6000/rs6000.cc | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/gcc/config/rs6000/rs6000.cc b/gcc/config/rs6000/rs6000.cc
index d18e262d81de..e4dc629ddcc9 100644
--- a/gcc/config/rs6000/rs6000.cc
+++ b/gcc/config/rs6000/rs6000.cc
@@ -3940,8 +3940,9 @@ rs6000_option_override_internal (bool global_init_p)
       rs6000_isa_flags &= ~OPTION_MASK_FPRND;
     }
 
-  if (TARGET_P8_VECTOR && !TARGET_ALTIVEC)
-    rs6000_isa_flags &= ~OPTION_MASK_P8_VECTOR;
+  /* Assert !TARGET_VSX if !TARGET_ALTIVEC and make some adjustments
+     based on either !TARGET_VSX or !TARGET_ALTIVEC concise.  */
+  gcc_assert (TARGET_ALTIVEC || !TARGET_VSX);
 
   if (TARGET_P8_VECTOR && !TARGET_VSX)
     rs6000_isa_flags &= ~OPTION_MASK_P8_VECTOR;