Hi! On Fri, 12 Jul 2013 18:53:58 +0200, Jakub Jelinek <ja...@redhat.com> wrote: > On Fri, Jul 12, 2013 at 09:49:28AM -0700, Thomas Schwinge wrote: > > On Fri, 12 Jul 2013 16:54:21 +0200 (CEST), Marc Glisse > > <marc.gli...@inria.fr> wrote: > > > this patch makes the driver pass -O2 to GNU ld if gcc was called with -O3 > > > (or more), -Ofast or -Os. > > > > I wondered about this before: why are no -O flags are passed to the (GNU) > > linker. > > > > What's the rationale for the mapping you propose of GCC and linker > > optimization flags? Why not a one-to-one mapping? > > Because there is no 1:1 mapping. I bet ld doesn't grok -Os or -Ofast or > -Og, and what -O* does in the linker doesn't have direct correspondence to > what -O* does in the compiler. Last time I've looked, -O* in the linker > just enabled some link time expensive computation of the hash table, > so enabling -O in the linker for -O1 in the compiler is definitely not a > good idea, similarly for -Og, those definitely want speed rather than better > hash table.
OK, there currently is no one-to-one mapping -- but why not establish one? Then the linker would enable the expensive optimizations only for -O2 and higher -- which would break backwards compatibility, bummer... (Though, I could see potential uses in the linker for -Ofast and -Og, too.) Grüße, Thomas
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