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Re: [PATCH] Fix PR37053: Move tweaks of commutative precedence to target hook
- From: Paolo Bonzini <paolo dot bonzini at gmail dot com>
- To: Peter Bergner <bergner at vnet dot ibm dot com>
- Cc: Maxim Kuvyrkov <maxim at codesourcery dot com>, gcc-patches <gcc-patches at gcc dot gnu dot org>, Paolo Bonzini <bonzini at gnu dot org>, Ian Lance Taylor <iant at google dot com>, Luis Machado <luisgpm at linux dot ibm dot com>
- Date: Fri, 26 Jun 2009 18:40:57 +0200
- Subject: Re: [PATCH] Fix PR37053: Move tweaks of commutative precedence to target hook
- References: <4A44D817.firstname.lastname@example.org> <1246031128.5284.45.camel@otta>
Peter Bergner wrote:
On Fri, 2009-06-26 at 18:15 +0400, Maxim Kuvyrkov wrote:
The attached patch fixes PR37053
The problem was introduced by patch for PR28690
hunk); this hunk causes ICE on m68k (and, possibly, other) architectures.
My first impulse was to remove the pointer tweak; but, well, if PowerPC
really benefits from it,
I will say we worked for a long time coming up with the patch we did so
that it didn't affect other arches. In particular, HJ ran a lot of
performance tests to make sure it didn't degrade performance on x86.
I cannot say I like Maxim's patch and he knows, but unfortunately, m68k
apparently implements 2-address arithmetic in a different way than x86
(or with other constraint) and we're talking about a lot of ICEs there. :-(
Another possibility, which you would have to try on PowerPC, could be to
limit the change of precedence to before reload. That would be a
simpler patch and one that does not risk slowing down the compiler that
tiny 0.1% that sums up quickly. But it would also be pretty magical...