Re: 8086 register allocation

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From	Hans-Peter Diettrich <DrDiettrich1@netscape.net>
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Subject	Re: 8086 register allocation
Date	Tue, 11 May 2021 09:35:17 +0200
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On 5/11/21 3:35 AM, Hans-Peter Diettrich wrote:

> A stack machine is convenient for calculations. Before the stack
> overflows the compiler can save intermediate results, as with any other
> architecture of limited register count.
>
> DoDi
> [Normal stack machines have the top few entries in registers and do the
> spilling to memory in hardware.  The x87 stack has 8 registers, which is
> a lot for a stack machine, but the spilling was broken.   You can address
> into the stack but you can't really use it as a register machine. -John]

FORTH coders know how inconvenient for humans is accessing "local
variables" in such a stack. But a compiler can track the content of the
stack.

I had some problems in understanding "spilling". After re-reading the
80287 instruction set I found that only ST(0) is usable for memory
load/store operations, making it hard to code load/store the other end
of the register stack. Thanks, John, for the kick... ;-)

DoDi

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8086 register allocation "Alexei A. Frounze" <alexfrunews@gmail.com> - 2021-05-09 14:28 -0700
  Re: 8086 register allocation Fernando <pronesto@gmail.com> - 2021-05-10 04:46 -0700
  Re: 8086 register allocation gah4 <gah4@u.washington.edu> - 2021-05-10 14:49 -0700
    Re: 8086 register allocation Hans-Peter Diettrich <DrDiettrich1@netscape.net> - 2021-05-11 03:35 +0200
      Re: 8086 register allocation gah4 <gah4@u.washington.edu> - 2021-05-10 21:19 -0700
      Re: 8086 register allocation Hans-Peter Diettrich <DrDiettrich1@netscape.net> - 2021-05-11 09:35 +0200
    Re: 8086 register allocation Thomas Koenig <tkoenig@netcologne.de> - 2021-05-11 06:44 +0000

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