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target/arm: Implement new v8.1M VLLDM and VLSTM encodings

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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
This commit is contained in:
Peter Maydell 2020-11-19 21:56:09 +00:00
parent 3423fbf104
commit fe6fa228a7
2 changed files with 26 additions and 1 deletions
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2
target/arm/m-nocp.decode
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@ -36,7 +36,7 @@
{
# Special cases which do not take an early NOCP: VLLDM and VLSTM
VLLDM_VLSTM 1110 1100 001 l:1 rn:4 0000 1010 0000 0000
VLLDM_VLSTM 1110 1100 001 l:1 rn:4 0000 1010 op:1 000 0000
# VSCCLRM (new in v8.1M) is similar:
VSCCLRM 1110 1100 1.01 1111 .... 1011 imm:7 0 vd=%vd_dp size=3
VSCCLRM 1110 1100 1.01 1111 .... 1010 imm:8 vd=%vd_sp size=2