[swift-dev] Faster debug builds?

Michael Gottesman mgottesman at apple.com
Sun Aug 6 15:16:24 CDT 2017

> On Aug 6, 2017, at 11:11 AM, David Zarzycki via swift-dev <swift-dev at swift.org> wrote:
> Hello,
> Unless I’m missing a build-script flag, it seems to me that compiling the Swift stdlib with the unoptimized debug swift compiler takes about 15 minutes on a fast machine.

I am assuming that you mean a debug swift compiler building an optimized stdlib?

> Other than forcing the type checker to be optimized, what if any tricks can I use to building the stdlib faster with the debug compiler? Is there a way to tell Clang to enable the inliner and only the inliner during -O0 builds? I have an anecdotal experiment[1] that suggests that this would yield appreciably faster Swift stdlib builds with the debug compiler (and selfishly speaking, I can tolerate the minor impact on debugging that inlining does to otherwise unoptimized code).

Are building LLVM in release + Swift in debug? I.e.:

--release-debuginfo --debug-swift --force-optimized-typechecker

> Thanks!
> Dave
> [1] – If one force inlines LLVM’s casting logic and associated callbacks (like classof() and getKind()), then the Swift stdlib builds 18% faster on my machine with the debug Swift compiler. One can imagine how much faster the whole stdlib would compile if all trivial functions were inlined automatically.
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