[Issue 14431] [REG 2.067.0] huge slowdown of compilation speed (page 2)

https://issues.dlang.org/show_bug.cgi?id=14431 weaselcat <r9shackleford@gmail.com> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |r9shackleford@gmail.com --- Comment #11 from weaselcat <r9shackleford@gmail.com> --- Hi, maybe it's best to promote CyberShadow's "Are we slim yet?" histogram tool? It was able to easily pinpoint exactly which commit caused this. http://digger.k3.1azy.net/trend/ maybe some sort of automated regression alert. Bye. --

June 27, 2015

[Issue 14431] [REG 2.067.0] huge slowdown of compilation speed

Posted by Walter Bright

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Walter Bright

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https://issues.dlang.org/show_bug.cgi?id=14431

Walter Bright <bugzilla@digitalmars.com> changed:

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--- Comment #12 from Walter Bright <bugzilla@digitalmars.com> ---
(In reply to Martin Nowak from comment #7)
> This slowdown comes from https://github.com/D-Programming-Language/dmd/pull/4384, which does instantiate additional templates in order to resolve link bugs. The problem is amplified by using single file compilation.

The trouble is the compiler would not instantiate a template if that template was already instantiated by an imported model, on the assumption that the instantiation would exist in the object code generated when the imported module was separately compiled.

The problem was that if A imports B, and B imports A, A and B are compiled separately, and so the template was never instantiated (see https://issues.dlang.org/show_bug.cgi?id=2644). The 4384 fixed this by always instantiating templates if the imported module also imported root modules, as computed by TemplateInstance::needsCodegen().

The trouble with that, and the slowdown, is the commonplace practice of having every module in a project import every other module.

An obvious workaround for users is to compile modules that mutually import each other on the same command to dmd.

A possible solution to this was proposed by Martin Nowak:

"I think we should define a rule for which module is responsible for the instantiation when they mutually import each other. I'd suggest that the module with the lexicographically smaller module name does it."

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https://issues.dlang.org/show_bug.cgi?id=14431 Kenji Hara <k.hara.pg@gmail.com> changed: What |Removed |Added ---------------------------------------------------------------------------- Keywords| |performance, pull --- Comment #13 from Kenji Hara <k.hara.pg@gmail.com> --- https://github.com/D-Programming-Language/dmd/pull/4784 --

https://issues.dlang.org/show_bug.cgi?id=14431 Walter Bright <bugzilla@digitalmars.com> changed: What |Removed |Added ---------------------------------------------------------------------------- See Also| |https://issues.dlang.org/sh | |ow_bug.cgi?id=14508 --

https://issues.dlang.org/show_bug.cgi?id=14431 --- Comment #14 from github-bugzilla@puremagic.com --- Commits pushed to stable at https://github.com/D-Programming-Language/dmd https://github.com/D-Programming-Language/dmd/commit/6c14fadca403a61a578795ec0fb71f9340c7b543 fix Issue 14431 - huge slowdown of compilation speed In the pull request #4384, all instance has been changed to invoke semantic3(). It was for the link-failure issue in specific case, but it was too excessive. 1. Semantic analysis strategy for template instances: We cannot determine which instance does not need to be placed in object file until semantic analysis completed. Therefore, for all templates instantiated in root module, compiler should invoke their semantic3 -- regardless of whether those are also instantiated in non-root module. If a template is _only_ instantiated in non-root module, we can elide its semantic3 (and for the compilation speed we should do that). 2. Code generation strategy for template instances: If a template is instantiated in non-root module, compiler usually does not have to put it in object file. But if a template is instantiated in both of root and non-root modules which mutually import each other, it needs to placed in objfile. https://github.com/D-Programming-Language/dmd/commit/92fcc9da72e2889406031a34d9a5d22b075f7d50 Merge pull request #4944 from 9rnsr/fix14431 [REG 2.067.0] Issue 14431 - huge slowdown of compilation speed --

https://issues.dlang.org/show_bug.cgi?id=14431 --- Comment #15 from github-bugzilla@puremagic.com --- Commits pushed to master at https://github.com/D-Programming-Language/dmd https://github.com/D-Programming-Language/dmd/commit/6c14fadca403a61a578795ec0fb71f9340c7b543 fix Issue 14431 - huge slowdown of compilation speed https://github.com/D-Programming-Language/dmd/commit/92fcc9da72e2889406031a34d9a5d22b075f7d50 Merge pull request #4944 from 9rnsr/fix14431 --

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