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cmd/compile/internal/types: lazy/incremental type expansion #25056

mdempsky opened this issue Apr 24, 2018 · 4 comments


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commented Apr 24, 2018

The compiler now supports an indexed data format for package export data that enables efficient random-access of package data. We already use this to implement lazy expansion of declarations and inline bodies, but we still currently fully expand types whenever they're referenced. I expect in larger projects that a lot of deeply nested details are never needed and we could avoid reading that data into memory.

I think the steps are largely:

  1. Hide remaining Type fields behind setter/getter methods.
  2. Create a new TSTUB Type with a way to register an expander function that rewrites the Type into a real Go type.
  3. Add a Type.expand method that checks for Etype==TSTUB and calls the expander function.
  4. Insert calls to expand() at the top of every(?) public Type method.
  5. Update iimport.go to create TSTUB types instead of normal types.

Another useful (but non-critical) step would be to review the Type API and try to prune/simplify unnecessary methods. This would reduce how many places we need to instrument with expand calls.

@mdempsky mdempsky added the ToolSpeed label Apr 24, 2018

@mdempsky mdempsky added this to the Go1.11 milestone Apr 24, 2018


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commented Apr 24, 2018

Optimistically tagging for 1.11, but freeze is one week away, so this will probably slip.


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commented Apr 24, 2018

Change mentions this issue: cmd/compile/internal/types: replace Type.Val with Type.Elem

gopherbot pushed a commit that referenced this issue Apr 24, 2018

cmd/compile/internal/types: replace Type.Val with Type.Elem
This reduces the API surface of Type slightly (for #25056), but also
makes it more consistent with the reflect and go/types APIs.

Passes toolstash-check.

Change-Id: Ief9a8eb461ae6e88895f347e2a1b7b8a62423222
Run-TryBot: Matthew Dempsky <>
TryBot-Result: Gobot Gobot <>
Reviewed-by: Brad Fitzpatrick <>

@mdempsky mdempsky modified the milestones: Go1.11, Go1.12 May 1, 2018


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commented May 1, 2018

Not happening for 1.11.


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commented Oct 30, 2018

Also not happening for 1.12.

@griesemer griesemer modified the milestones: Go1.12, Go1.13 Oct 30, 2018

@andybons andybons modified the milestones: Go1.13, Go1.14 Jul 8, 2019

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