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Re: [patch committed] Defaulting to -fno-ira-share-spill-slots on SH
- From: Jeff Law <law at redhat dot com>
- To: Kaz Kojima <kkojima at rr dot iij4u dot or dot jp>
- Cc: gcc-patches at gnu dot org
- Date: Wed, 12 Nov 2008 10:15:06 -0700
- Subject: Re: [patch committed] Defaulting to -fno-ira-share-spill-slots on SH
- References: <firstname.lastname@example.org>
Kaz Kojima wrote:
Hi,Seems like absolutely the wrong approach to me. I'm surprised we're
still having stack slot sharing problems with the patch for 37447 installed.
PR 37514 is a wrong-code problem on SH which is a 4.4 regression
started after the IRA merge. IRA makes spill slots shared if
possible when flag_ira_share_spill_slots set. In the above PR,
it causes a wrong sharing of slots on SH. I've been trying to
see why this sharing occurs but it's a hard problem for me.
With -fno-ira-share-spill-slots, the problem goes away, though
it increases the code sizes of several tests in CSiBE by ~10%.
Although this code size regression isn't ignorable, I think
that the wrong code problem is far bigger than that. I'd like
to work around this PR by defaulting to -fno-ira-share-spill-slots
on this target. The attached patch is for this. The patch also
adds a new target specific test to remember that the PR isn't fixed
yet. It's tested with bootstrap and the top level "make -k check"
on sh4-unknown-linux-gnu. The testsuite change is tested also
2008-11-10 Kaz Kojima <email@example.com>
* config/sh/sh.h (OPTIMIZATION_OPTIONS): Set
flag_ira_share_spill_slots to 2 if it's already non-zero.
(OVERRIDE_OPTIONS): Clear flag_ira_share_spill_slots if
flag_ira_share_spill_slots is 2.