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Re: Bad code generation on HPPA platform


Steve Ellcey wrote:
I am investigating a bad code generation bug on the 64 bit HPPA platform
with GCC 4.3.0 and would like some help and/or ideas on how to analyze
and fix it.  The failing test is the SPEC 2000 GCC benchmark (version
2.7.2.2) and I have been unable to create a smaller test case so far.

What I have found is that if I build GCC from version 127633 (after
applying the patch for PR middle-end/33029 so that the build will work)
I can build and run the SPEC GCC benchmark.  If I update GCC to version
127634 then the benchmark will abort when it is run.

The difference between those versions is this patch:

    2007-08-19  Andrew Pinski  <andrew_pinski@playstation.sony.com>
         PR middle-end/32940
         * cfgexpand.c  (expand_one_register_var): Mark pointer
         DECL_ARTIFICIAL as REG_POINTER also.
         * stmt.c (expand_decl): Likewise.

In the PR report for 32940 there is a pointer to:

http://gcc.gnu.org/ml/gcc-patches/2004-06/msg00020.html

That patch fixed a bootstrap problem on HPPA and reverting it (which is
what the patch for PR 32940 seems to do) seems to be reintroducing the
problem that the earlier patch was intended to fix.  While reverting
that patch didn't seem to cause bootstrap problems it does seem to cause
problems when building the older GCC version that is in SPEC2000.  Any
advise on how to proceed from here?

Steve Ellcey
sje@cup.hp.com

I'm well versed with the problems in this area and I'd be very leery of
Andrew's patch. There are some thorny issues in this space and I'm
far from 100% sure that blindly propagating a pointer type into REG_POINTER is always valid, particularly for compiler generated temporaries.




Can you describe better what you're seeing in the 2.7.2.2 build that's causing problems?

Jeff


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