Fix Issue 18362 - Try to enable lto for all dmd builds #492
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Thanks for your pull request, @maxhaton! Bugzilla references
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| @@ -371,6 +371,8 @@ void buildAll(Bits bits, string branch, bool dmdOnly=false) | |||
| } | |||
| auto hostDMDEnv = " HOST_DC="~hostDMD~" HOST_DMD="~hostDMD; | |||
| auto isRelease = " ENABLE_RELEASE=1"; | |||
| //Enable lto for everything. | |||
| auto ltoOption = " ENABLE_LTO=1"; | |||
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@maxhaton: Are you sure this actually works? I don't see ENABLE_LTO being forwarded to build.din https://github.com/dlang/dmd/blob/master/src/posix.mak#L100.
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GNU make sets ENABLE_LTO=1 as an environment variable which is read by build.d.
So make -f posix.mak ENABLE_LTO=1 works as expected.
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Hmm okay, but what about Windows with DigitalMars make? IIRC, there's a difference, and that's why all (?) other vars are forwarded explicitly. No ENABLE_LTO forwarding in https://github.com/dlang/dmd/blob/master/src/win32.mak#L75 either.
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DM make doesn't seem to forward command line variables. So it needs to be explicitly forwarded in win32.mak
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It's how I recorded the data. I think no one bothered to add it since it
makes the build extremely slow
…On Thu, 13 Jan 2022, 09:33 Martin Kinkelin, ***@***.***> wrote:
***@***.**** commented on this pull request.
------------------------------
In create_dmd_release/create_dmd_release.d
<#492 (comment)>:
> @@ -371,6 +371,8 @@ void buildAll(Bits bits, string branch, bool dmdOnly=false)
}
auto hostDMDEnv = " HOST_DC="~hostDMD~" HOST_DMD="~hostDMD;
auto isRelease = " ENABLE_RELEASE=1";
+ //Enable lto for everything.
+ auto ltoOption = " ENABLE_LTO=1";
@maxhaton <https://github.com/maxhaton>: Are you sure this actually
works? I don't see ENABLE_LTO being forwarded to build.din
https://github.com/dlang/dmd/blob/master/src/posix.mak#L100.
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Another way of achieving the same optimization results (more or less) but probably way faster would be to simply compile all of DMD to a single object file, instead of the 3 separate lexer/frontend/backend object files. |
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Hey @maxhaton, how did you generate and plot the graph? Do you use D for that as well? It would be interesting if you could capture the process. |
It was generated with mathematica, the data was collected with my own grubby mitts on the keyboard |
LTO isn't always plain sailing but let's try it.
A box & whisker plot of phobos test suite build times vs. flags