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Implement the "moffset" encoding size optimization in emitOutputAM - #62896
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ghost
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Dec 16, 2021
Tagging subscribers to this area: @JulieLeeMSFT Issue DetailsLet's see what the CI thinks.
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SingleAccretion
marked this pull request as ready for review
December 17, 2021 11:11
SingleAccretion
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Dec 17, 2021
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jakobbotsch
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Dec 19, 2021
jakobbotsch
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LGTM, thanks. Nice x86 diffs.
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The x86 encoding for direct addressing modes permits a short form for the case of
mov eax, [addr],mov [addr], eax, without the ModR/M byte. We were already taking advantage of it when emitting statics (inemitOutputCV). This change ports that optimization toemitOutputAM(the "general" method handling all address modes, not justMones).There is an unfortunate part to this change and that is the fact it consists of essentially copying code (verbatim, to signify that). I don't know what is the intention behind the
CV/AMsplit (they emit the same code on x64, and on x86, except for this special case), and I do not have the expertise necessary to refactor this with confidence, so that is why that is.There is a fortunate part to this change too though, and that is the fact it has some nice diffs attached to it. For unclear reasons, SPMI in CI did not capture them, so here is my locally obtained version: diffs.
As one would guess, this is another step in the direction of deleting
CLS_VAR.