[Bug tree-optimization/15353] [tree-ssa] Merge two "if"s if one subsumes the other.

["law at redhat dot com" <gcc-bugzilla at gcc dot gnu dot org>]

------- Additional Comments From law at redhat dot com  2005-08-11 17:29 -------
Subject: Re:  [tree-ssa] Merge two "if"s if
	one subsumes the other.

On Thu, 2005-08-11 at 15:52 +0000, trt at acm dot org wrote:
> ------- Additional Comments From trt at acm dot org  2005-08-11 15:52 -------
> I think http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21643 is closely related.
It's related.

However, there is a key difference.  In 21643, the object being tested
is a scalar and thus should be subject to optimization by fold-const.c's
range checking optimizations.  ie, the merging of the conditions in the
test should occur well before the SSA optimization path is run.

In 15353 the object being tested is a memory reference and thus we can
not safely merge the tests until later in the optimization path (after
we've exposed the memory loads and proved they're equivalent).

jeff




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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15353