Merge remote-tracking branch 'remotes/palmer/tags/riscv-for-master-4.0-sf4' into staging

target/riscv: Convert to decodetree

Bastian: this patchset converts the RISC-V decoder to decodetree in four major steps:

1) Convert 32-bit instructions to decodetree [Patch 1-15]:
    Many of the gen_* functions are called by the decode functions for 16-bit
    and 32-bit functions. If we move translation code from the gen_*
    functions to the generated trans_* functions of decode-tree, we get a lot of
    duplication. Therefore, we mostly generate calls to the old gen_* function
    which are properly replaced after step 2).

    Each of the trans_ functions are grouped into files corresponding to their
    ISA extension, e.g. addi which is in RV32I is translated in the file
    'trans_rvi.inc.c'.

2) Convert 16-bit instructions to decodetree [Patch 16-18]:
    All 16 bit instructions have a direct mapping to a 32 bit instruction. Thus,
    we convert the arguments in the 16 bit trans_ function to the arguments of
    the corresponding 32 bit instruction and call the 32 bit trans_ function.

3) Remove old manual decoding in gen_* function [Patch 19-29]:
    this move all manual translation code into the trans_* instructions of
    decode tree, such that we can remove the old decode_* functions.

Palmer: This, with some additional cleanup patches, passed Alistar's
testing on rv32 and rv64 as well as my testing on rv64, so I think it's
good to go.  I've run my standard test against this exact tag.

I still don't have a Mac to try this on, sorry!

# gpg: Signature made Wed 13 Mar 2019 13:44:49 GMT
# gpg:                using RSA key 00CE76D1834960DFCE886DF8EF4CA1502CCBAB41
# gpg:                issuer "palmer@dabbelt.com"
# gpg: Good signature from "Palmer Dabbelt <palmer@dabbelt.com>" [unknown]
# gpg:                 aka "Palmer Dabbelt <palmer@sifive.com>" [unknown]
# gpg: WARNING: This key is not certified with a trusted signature!
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# Primary key fingerprint: 00CE 76D1 8349 60DF CE88  6DF8 EF4C A150 2CCB AB41

* remotes/palmer/tags/riscv-for-master-4.0-sf4: (29 commits)
  target/riscv: Remove decode_RV32_64G()
  target/riscv: Remove gen_system()
  target/riscv: Rename trans_arith to gen_arith
  target/riscv: Remove manual decoding of RV32/64M insn
  target/riscv: Remove shift and slt insn manual decoding
  target/riscv: make ADD/SUB/OR/XOR/AND insn use arg lists
  target/riscv: Move gen_arith_imm() decoding into trans_* functions
  target/riscv: Remove manual decoding from gen_store()
  target/riscv: Remove manual decoding from gen_load()
  target/riscv: Remove manual decoding from gen_branch()
  target/riscv: Remove gen_jalr()
  target/riscv: Convert quadrant 2 of RVXC insns to decodetree
  target/riscv: Convert quadrant 1 of RVXC insns to decodetree
  target/riscv: Convert quadrant 0 of RVXC insns to decodetree
  target/riscv: Convert RV priv insns to decodetree
  target/riscv: Convert RV64D insns to decodetree
  target/riscv: Convert RV32D insns to decodetree
  target/riscv: Convert RV64F insns to decodetree
  target/riscv: Convert RV32F insns to decodetree
  target/riscv: Convert RV64A insns to decodetree
  ...

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>