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target/arm: Allow reading flags from FPSCR for M-profile 

rt==15 is a special case when reading the flags: it means the
destination is APSR. This patch avoids rejecting
vmrs apsr_nzcv, fpscr
as illegal instruction.

Cc: qemu-stable@nongnu.org
Signed-off-by: Christophe Lyon <christophe.lyon@linaro.org>
Message-id: 20191025095711.10853-1-christophe.lyon@linaro.org
[PMM: updated the comment]
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
This commit is contained in:
Christophe Lyon 2019-10-25 11:57:11 +02:00 committed by Peter Maydell
parent 98be6b7d62
commit 2529ab43b8
1 changed files with 3 additions and 2 deletions
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5
target/arm/translate-vfp.inc.c
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@ -703,9 +703,10 @@ static bool trans_VMSR_VMRS(DisasContext *s, arg_VMSR_VMRS *a)
if (arm_dc_feature(s, ARM_FEATURE_M)) {
/*
* The only M-profile VFP vmrs/vmsr sysreg is FPSCR.
* Writes to R15 are UNPREDICTABLE; we choose to undef.
* Accesses to R15 are UNPREDICTABLE; we choose to undef.
* (FPSCR -> r15 is a special case which writes to the PSR flags.)
*/
if (a->rt == 15 || a->reg != ARM_VFP_FPSCR) {
if (a->rt == 15 && (!a->l || a->reg != ARM_VFP_FPSCR)) {
return false;
}
}