[PATCH] CodeGen target hook for emitting intrinsic or libcall for pow*

Eli Bendersky eliben at google.com
Wed Jul 10 14:40:41 PDT 2013

>> I'm not asking you to wrap the driver.  I'm asking you to change clang's
>> driver logic when targeting *-*-nacl to use the existing logic to suppress
>> builtin treatment of functions.
> Oh, it turns out Clang does not currently support -fno-builtin-<FUNC> at
> all:
> http://llvm.org/bugs/show_bug.cgi?id=4941
> What functions do you want to opt out of builtin treatment?  All of them?
>  Just math functions?

For starters, math functions. There aren't many libc math functions handled
there, BTW. When I was working on the original patch I dug through history
- a couple were added (pow and sqrt) I think, and sqrt was then backed off
due to some problems. Even with pow there are other constrains such as
errno (the builtin is not generated when we want errno, naturally, even
without -fno-builtins). Perhaps I can make the target hook more generic -
controlling all math libraries (the BIfoo ones, not BI__builtin_foo)
instead of just pow?

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