Groups > comp.compilers > #1930

Re: Opcode handler dispatch in an interpreter: Implementing switch on OpCode.

From	Hans-Peter Diettrich <DrDiettrich1@netscape.net>
Newsgroups	comp.compilers
Subject	Re: Opcode handler dispatch in an interpreter: Implementing switch on OpCode.
Date	2017-10-11 18:12 -0400
Organization	Compilers Central
Message-ID	<17-10-020@comp.compilers> (permalink)
References	<17-10-001@comp.compilers> <17-10-004@comp.compilers> <17-10-009@comp.compilers> <17-10-011@comp.compilers> <17-10-014@comp.compilers>

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Am 08.10.2017 um 20:36 schrieb George Neuner:

> Some of the things to come out of the discussions in c.l.a.x86 were
> that the fastest [simple] JIT sequence for an interpreter is a list of
> explicit call instructions: e.g.,
>
>     call <bytecode_function>
>     call <bytecode_function>
>       :
>
> rather than a list of function addresses with a dispatcher.   This is
> because the call leverages the CPU branch predictor rather than
> fighting with it.

I'm not sure about a single common instruction cache and branch
prediction architecture, the behaviour may differ amongst architectures.
The memory bus interface instead should be similar in all architectures,
so that it should speed up execution if function code is aligned to the
machine's data bus width (size of a chache line). This will make
available the highest possible number of sequential instructions after
the first read at a non-sequential (jump/call) address.

Tail threading instead can benefit from micro code, if that instruction
sequence can be implemented in a single dedicated micro code sequence.
Again this behaviour depends heavily on the particular machine
architecture. Perhaps more instruction sequences in the emulator code
can be optimized this way?

DoDi

Thread

Opcode handler dispatch in an interpreter: Implementing switch on OpCode. Robert Jacobson <rljacobson@gmail.com> - 2017-10-05 09:29 -0700
  Re: Opcode handler dispatch in an interpreter: Implementing switch on OpCode. bartc <bc@freeuk.com> - 2017-10-05 21:14 +0100
  Re: Opcode handler dispatch in an interpreter: Implementing switch on OpCode. Hans-Peter Diettrich <DrDiettrich1@netscape.net> - 2017-10-06 02:56 +0200
    Re: Opcode handler dispatch in an interpreter: Implementing switch on OpCode. George Neuner <gneuner2@comcast.net> - 2017-10-07 12:55 -0400
      Re: Opcode handler dispatch in an interpreter: Implementing switch on OpCode. bartc <bc@freeuk.com> - 2017-10-07 19:05 +0100
        Re: Opcode handler dispatch in an interpreter: Implementing switch on OpCode. George Neuner <gneuner2@comcast.net> - 2017-10-08 14:36 -0400
          Re: Opcode handler dispatch in an interpreter: Implementing switch on OpCode. bartc <bc@freeuk.com> - 2017-10-08 22:49 +0100
            Re: Opcode handler dispatch in an interpreter: Implementing switch on OpCode. Hans-Peter Diettrich <DrDiettrich1@netscape.net> - 2017-10-11 18:13 -0400
              Re: Opcode handler dispatch in an interpreter: Implementing switch on OpCode. bartc <bc@freeuk.com> - 2017-10-17 15:54 -0400
          Re: Opcode handler dispatch in an interpreter: Implementing switch on OpCode. bartc <bc@freeuk.com> - 2017-10-11 18:12 -0400
          Re: Opcode handler dispatch in an interpreter: Implementing switch on OpCode. Hans-Peter Diettrich <DrDiettrich1@netscape.net> - 2017-10-11 18:12 -0400
            Re: Opcode handler dispatch in an interpreter: Implementing switch on OpCode. George Neuner <gneuner2@comcast.net> - 2017-10-17 15:55 -0400
      Re: Opcode handler dispatch in an interpreter: Implementing switch on OpCode. anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-10-08 13:41 +0000
  Re: Opcode handler dispatch in an interpreter: Implementing switch on OpCode. anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-10-06 22:32 +0000

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