[patch] Fix ICE in set_lattice_value

[Eric Botcazou]

This is a regression present on mainline and 4.7 branch for targets using SJLJ 
exceptions by default in Ada (e.g. ARM).  The error message is:

+===========================GNAT BUG DETECTED==============================+
| 4.8.0 20120716 (experimental) [trunk revision 189525] (x86_64-suse-linux) GCC 
error:|
| in set_lattice_value, at tree-ssa-ccp.c:452                              |
| Error detected around p.adb:16:4  

It's valid_lattice_transition returning false on a transition from INTEGER_CST 
to a constant &x.  It occurs for an array reference with non-constant index: on 
the first round, &x + i is non-constant so the algorithm computes an alignment 
factor which is an INTEGER_CST; on the second round, i is 0 so the new value is 
the constant &x.

valid_lattice_transition accepts the reverse transition.  The attached patch 
makes the function accept this transition as well.

Tested on x86_64-suse-linux, OK for the mainline and 4.7 branch?


2012-07-18  Eric Botcazou  <ebotcazou@adacore.com>

	* tree-ssa-ccp.c (valid_lattice_transition): Allow transitioning from
	as well as to INTEGER_CST.


2012-07-18  Eric Botcazou  <ebotcazou@adacore.com>

	* gnat.dg/loop_optimization11.adb: New test.
	* gnat.dg/loop_optimization11_pkg.ads: New helper.


-- 
Eric Botcazou
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