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. 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).



[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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