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Re: [lto] make builtins go

From: Paolo Bonzini <bonzini at gnu dot org>
To: Mark Mitchell <mark at codesourcery dot com>
Cc: GCC Patches <gcc-patches at gcc dot gnu dot org>, Nathan Froyd <froydnj at codesourcery dot com>
Date: Tue, 11 Dec 2007 11:03:26 +0100
Subject: Re: [lto] make builtins go
References: <20071129220256.GN24671@codesourcery.com> <475D42B9.3080106@gnu.org> <475D9FFD.2020900@codesourcery.com>

1. If "f" calls "sin", and "f" is compiled with -fno-builtin-sin, and
"g" calls "f", and "g" is compiled with -fbuiltin-sin, should we perform
builtin optimizations?

2. If "f" calls "sin" and was compiled without optimization (e.g., "-g")
 but, now, at LTO-time, is compiled with "-O2", should we perform
builtin optimizations?

I think that for (1), it makes sense not to optimize, but for (2) it
makes more sense to optimize.  But, I also think your suggestion is
reasonable, and it does have the advantage of seeming simplest to reason
about.

I don't think my suggestion prevents optimizing (2). :-) In the (2) case __builtin_sin will be serialized out (because -O0 does not imply -fno-builtin), read in by LTO, and optimize.

Paolo

Follow-Ups:
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References:
- Re: [lto] make builtins go
  - From: Paolo Bonzini
- Re: [lto] make builtins go
  - From: Mark Mitchell

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