target/arm: Fix has_vfp/has_neon ID reg squashing for M-profile
In arm_cpu_realizefn(), if the CPU has VFP or Neon disabled then we
squash the ID register fields so that we don't advertise it to the
guest. This code was written for A-profile and needs some tweaks to
work correctly on M-profile:
* A-profile only fields should not be zeroed on M-profile:
- MVFR0.FPSHVEC,FPTRAP
- MVFR1.SIMDLS,SIMDINT,SIMDSP,SIMDHP
- MVFR2.SIMDMISC
* M-profile only fields should be zeroed on M-profile:
- MVFR1.FP16
In particular, because MVFR1.SIMDHP on A-profile is the same field as
MVFR1.FP16 on M-profile this code was incorrectly disabling FP16
support on an M-profile CPU (where has_neon is always false). This
isn't a visible bug yet because we don't have any M-profile CPUs with
FP16 support, but the change is necessary before we introduce any.
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Message-id:
20201019151301.2046-9-peter.maydell@linaro.org