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Re: optimization/6822: GCC 3.1.1 - Internal compiler error in extract_insn, at recog.c:2132


http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=6822

I believe the following patch is the cause of this PR:

2002-05-15  Eric Botcazou  <ebotcazou@multimania.com>

	* fold-const.c (fold) [LT_EXPR]: Move the transformation of a
	comparison against the highest or lowest integer value before
	the 'X >= CST to X > (CST - 1)' and 'X < CST to X <= (CST - 1)'
	transformation and that of an unsigned comparison against 0
	right after.

Previously, unsigned X < 128 would be converted to unsigned X <= 127 and
then optimized to signed X >= 0.  After changing the order of the
transformations, the compiler only reduces the expression to X <= 127 ???
The result is the reported ICE.  This could very well be a latent bug
in other parts of the compiler, but it seems the change results in missed
opportunities to simplify expressions.  I'll post an alternative patch
in my next message...

- Glen Nakamura


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