On Tue, 22 Apr 2014 08:45:31 +0000 (UTC) Martin Vaeth <mar...@mvath.de> wrote:
> Ryan Hill <rh...@gentoo.org> wrote: > > > > One thing I forgot to mention - LTO can also have detrimental effect on > > certain architectures. On some (eg. ppc), performance can actually > > be degraded due to increased register pressure. > > If this really is the case it is not the problem of LTO but > of the optimizer: If the optimizer really produces *worse* > code when he *can* see the full program instead of only parts of it, > something is severely broken in the optimizer. Only decreasing the > possibilities of the optimizer by removing LTO would be the wrong way > to "solve" this problem. Yes, this is a problem caused by aggressive inlining, and is being worked on upstream[1]. I meant that currently released versions exhibit this behaviour. [1] see for example http://gcc.gnu.org/ml/gcc-patches/2014-04/msg01098.html -- Ryan Hill psn: dirtyepic_sk gcc-porting/toolchain/wxwidgets @ gentoo.org 47C3 6D62 4864 0E49 8E9E 7F92 ED38 BD49 957A 8463
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