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Date: Sun, 15 Jan 2023 04:35:22 +0000 (GMT)
From: "Maciej W. Rozycki" <macro@orcam.me.uk>
To: Jan Beulich <jbeulich@suse.com>
cc: Binutils <binutils@sourceware.org>, Palmer Dabbelt <palmer@dabbelt.com>, 
    Andrew Waterman <andrew@sifive.com>, Jim Wilson <jim.wilson.gcc@gmail.com>, 
    Nelson Chu <nelson@rivosinc.com>
Subject: Re: [PATCH 1/3] RISC-V: prefer SLT{,U} aliases for SLTI{,U}
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On Fri, 13 Jan 2023, Jan Beulich via Binutils wrote:

> While not spelled out by the spec, gas has been supporting these aliases
> virtually forever. Yet they were unused by the disassembler because of
> sitting later in the table. Move the non-aliases down.

 I think this is going backwards.  Aliases are used in disassembly to 
improve readability, e.g. to show `nop', rather than `c.addi zero,0' which 
would make anyone scratch their head, at least initially.

 In this case there's no improvement, but obfuscation, as you're losing 
the clear distinction between the register and the immediate instructions 
and one will have to examine the operands to spot the difference.

 The alternative mnemonic forms for immediate machine instructions are 
there (NB pinched from the MIPS assembly dialect) to make it easier for 
people to write handcoded assembly, especially where macros are involved, 
either GAS or C preprocessor ones, and not for disassembly.  Conceptually 
they're assembly macros that expand to a single instruction rather than 
aliases.  IOW it's not a bug that those are not considered aliases for 
disassembly.

 Likewise with the remaining patches in this series.

  Maciej