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

[John McCall]

On Jul 10, 2013, at 11:39 AM, Eli Bendersky <eliben at google.com> wrote:
> On Wed, Jul 10, 2013 at 11:26 AM, John McCall <rjmccall at apple.com> wrote:
> On Jul 10, 2013, at 11:18 AM, Eli Bendersky <eliben at google.com> wrote:
>> On Wed, Jul 10, 2013 at 3:03 AM, John McCall <rjmccall at apple.com> wrote:
>> On Jun 27, 2013, at 3:57 PM, Eli Bendersky <eliben at google.com> wrote:
>> > Without fmath-errno, Clang currently generates calls to @llvm.pow.* intrinsics when it sees pow*(). This may not be suitable for all targets (for example PNaCl), so the attached patch adds a target hook that CodeGen queries. The target can state its preference for having or not having the intrinsic generated. Non-PNaCl behavior remains unchanged; PNaCl-specific test added.
>> 
>> Isn't a more straightforward and less invasive approach to just invoke the compiler with -fno-builtin=pow or something along those lines?
>> 
>> We don't control the flags users supply to Clang though. 
> 
> Then handle it in the driver.
> 
> Would that not be more intrusive, then? Or perhaps I'm misunderstanding what you're proposing.

It would be isolated to target-specific logic in target-specific parts of the toolchain instead of inventing a new option that's basically "do what PNaCl wants" and then propagating it through the entire compiler.

John.

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