v8.1M adds new encodings of VLLDM and VLSTM (where bit 7 is set).
The only difference is that:
* the old T1 encodings UNDEF if the implementation implements 32
Dregs (this is currently architecturally impossible for M-profile)
* the new T2 encodings have the implementation-defined option to
read from memory (discarding the data) or write UNKNOWN values to
memory for the stack slots that would be D16-D31
We choose not to make those accesses, so for us the two
instructions behave identically assuming they don't UNDEF.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20201119215617.29887-21-peter.maydell@linaro.org
Implement the v8.1M VSCCLRM insn, which zeros floating point
registers if there is an active floating point context.
This requires support in write_neon_element32() for the MO_32
element size, so add it.
Because we want to use arm_gen_condlabel(), we need to move
the definition of that function up in translate.c so it is
before the #include of translate-vfp.c.inc.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20201119215617.29887-5-peter.maydell@linaro.org
From v8.1M, disabled-coprocessor handling changes slightly:
* coprocessors 8, 9, 14 and 15 are also governed by the
cp10 enable bit, like cp11
* an extra range of instruction patterns is considered
to be inside the coprocessor space
We previously marked these up with TODO comments; implement the
correct behaviour.
Unfortunately there is no ID register field which indicates this
behaviour. We could in theory test an unrelated ID register which
indicates guaranteed-to-be-in-v8.1M behaviour like ID_ISAR0.CmpBranch
>= 3 (low-overhead-loops), but it seems better to simply define a new
ARM_FEATURE_V8_1M feature flag and use it for this and other
new-in-v8.1M behaviour that isn't identifiable from the ID registers.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20201019151301.2046-3-peter.maydell@linaro.org
For M-profile CPUs, the architecture specifies that the NOCP
exception when a coprocessor is not present or disabled should cover
the entire wide range of coprocessor-space encodings, and should take
precedence over UNDEF exceptions. (This is the opposite of
A-profile, where checking for a disabled FPU has to happen last.)
Implement this with decodetree patterns that cover the specified
ranges of the encoding space. There are a few instructions (VLLDM,
VLSTM, and in v8.1 also VSCCLRM) which are in copro-space but must
not be NOCP'd: these must be handled also in the new m-nocp.decode so
they take precedence.
This is a minor behaviour change: for unallocated insn patterns in
the VFP area (cp=10,11) we will now NOCP rather than UNDEF when the
FPU is disabled.
As well as giving us the correct architectural behaviour for v8.1M
and the recommended behaviour for v8.0M, this refactoring also
removes the old NOCP handling from the remains of the 'legacy
decoder' in disas_thumb2_insn(), paving the way for cleaning that up.
Since we don't currently have a v8.1M feature bit or any v8.1M CPUs,
the minor changes to this logic that we'll need for v8.1M are marked
up with TODO comments.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20200803111849.13368-6-peter.maydell@linaro.org
Peter Maydell