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PDP-11: expensive (in terms of backend binary size) optimizations: - #189

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shattered wants to merge 2 commits into
davidgiven:masterfrom
shattered:_f9be81d1
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shattered wants to merge 2 commits into
davidgiven:masterfrom
shattered:_f9be81d1

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@shattered

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  • use register cache whenever possible
  • use indirect addressing modes in ALU and compare insns
  • use TST and CMP in place of ADD, when possible
  • use byte swap and rotate insns to speed up shifts
  • etc.

r16n0/r32n0 workarounds are still necessary to avoid deadlocks in register allocator.

There's also a workaround for cowasm bug -- "-1(Rn)" is a syntax error.

- use register cache whenever possible
- use indirect addressing modes in ALU and compare insns
- use TST and CMP in place of ADD, when possible
- use byte swap and rotate insns to speed up shifts
- etc.

r16n0/r32n0 workarounds are still necessary to avoid deadlocks in
register allocator.
@shattered

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ping?

@davidgiven

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Looks good to me; could you take a look at the resolve conflict? You did both parts of that code and know how it works.

@shattered

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I'll rework this

@shattered shattered closed this Sep 25, 2026
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2 participants