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

From: Bastian Koppelmann
Subject: Re: [Qemu-riscv] [Qemu-devel] [PATCH v5 00/35] target/riscv: Convert to decodetree
Date: Wed, 23 Jan 2019 10:15:10 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0

On 1/22/19 10:38 PM, Richard Henderson wrote:
On 1/22/19 1:28 AM, Bastian Koppelmann wrote:

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 
     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

2) Convert 16-bit instructions to decodetree [Patch 17-19]:
     All 16 bit instructions have a direct mapping to a 32 bit instruction. 
     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


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.

Thanks for your great reviews. I'll do a final respin to fix the funky indentations. Alistair do you want to pick up the series?



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