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Re: [Qemu-riscv] [PATCH v5 00/35] target/riscv: Convert to decodetree

From: Richard Henderson
Subject: Re: [Qemu-riscv] [PATCH v5 00/35] target/riscv: Convert to decodetree
Date: Tue, 22 Jan 2019 13:38:52 -0800
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0

On 1/22/19 1:28 AM, Bastian Koppelmann wrote:
> Hi,
> this patchset converts the RISC-V decoder to decodetree in four major steps:
> 1) Convert 32-bit instructions to decodetree [Patch 1-16]:
>     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 17-19]:
>     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 20-30]:
>     this move all manual translation code into the trans_* instructions of
>     decode tree, such that we can remove the old decode_* functions.
> 4) Simplify RVC by reusing as much as possible from the RVG decoder as 
> suggested
>    by Richard. [Patch 31-35]
> full tree available at
> https://github.com/bkoppelmann/qemu/tree/riscv-dt-v5
> Cheers,
> Bastian
> v4 -> v5:
>     - fixed rebase error
>     - moved TARGET_LONG_BITS check of shift instructions before rd == 0 check
>     - removed extra sign extension of sraiw
>     - removed rs2 == 0 special cases in sraw/srlw

All looks good to me now.  Thanks for persevering.


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