[gcc r11-8245] arm: partial revert of r11-8168 [PR100067]

[gcc r11-8245] arm: partial revert of r11-8168 [PR100067]

[Richard Earnshaw]

https://gcc.gnu.org/g:3bffc4b37e85c7f6092dfb0fbe4067d268e97b46

commit r11-8245-g3bffc4b37e85c7f6092dfb0fbe4067d268e97b46
Author: Richard Earnshaw <rearnsha@arm.com>
Date:   Mon Apr 19 16:56:31 2021 +0100

    arm: partial revert of r11-8168 [PR100067]
    
    This is a partial revert of r11-8168.  The overall purpose of the
    commit is retained (to fix a bogus warning when -mfpu=<not-auto> is
    used in combination with eg -mcpu=neoverse-v1), but it removes the
    hunk that changed the subsequent feature bits for features of a
    simd/fp unit that cannot be described by -mfpu.  While I still think
    that is the correct direction of travel, it's somewhat disruptive and
    not appropriate for late stage4.  I'll revisit for gcc-12.
    
    gcc:
            PR target/100067
            * config/arm/arm.c (arm_configure_build_target): Do not strip
            extended FPU/SIMD feature bits from the target ISA when -mfpu
            is specified (partial revert of r11-8168).

Diff:
---
 gcc/config/arm/arm.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/gcc/config/arm/arm.c b/gcc/config/arm/arm.c
index 475fb0d827f..340f7c95d76 100644
--- a/gcc/config/arm/arm.c
+++ b/gcc/config/arm/arm.c
@@ -3396,9 +3396,11 @@ arm_configure_build_target (struct arm_build_target *target,
       auto_sbitmap fpu_bits (isa_num_bits);
 
       arm_initialize_isa (fpu_bits, arm_selected_fpu->isa_bits);
-      /* Clear out ALL bits relating to the FPU/simd extensions, to avoid
-	 potentially invalid combinations later on that we can't match.  */
-      bitmap_and_compl (target->isa, target->isa, isa_all_fpbits);
+      /* This should clear out ALL bits relating to the FPU/simd
+	 extensions, to avoid potentially invalid combinations later on
+	 that we can't match.  At present we only clear out those bits
+	 that can be set by -mfpu.  This should be fixed in GCC-12.  */
+      bitmap_and_compl (target->isa, target->isa, isa_all_fpubits_internal);
       bitmap_ior (target->isa, target->isa, fpu_bits);
     }