[comitted] arm: partial revert of r11-8168 [PR100067]

[comitted] arm: partial revert of r11-8168 [PR100067]

[Richard Earnshaw]

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From: Richard Earnshaw <rearnsha@arm.com>

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


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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);
     }