[patch] Fix PR middle-end/56474

[Eric Botcazou]

Hi,

this is a regression present on the mainline and 4.8 branch and introduced by 
the latest series of sizetype changes.  Associated adjustments were made in 
the various front-ends for it, most notably Ada which was the most affected, 
but this issue slipped through the cracks in the form of a bogus overflow 
detection for 0-based arrays with variable upper bound included in a record 
with discriminant.

The proposed fix is to disable overflow detection in sizetype for one special 
case (0 - 1) in size_binop_loc.  An equivalent kludge was added to layout_type 
to disable overflow detection for the size expression of [0, -1] arrays.

Tested on x86_64-suse-linux, OK for the mainline and 4.8 branch?


2013-04-14  Eric Botcazou  <ebotcazou@adacore.com>

	PR middle-end/56474
	* fold-const.c (size_binop_loc): Disable overflow detection for 0 - 1.


2013-04-14  Eric Botcazou  <ebotcazou@adacore.com>

	* gnat.dg/specs/array3.ads: New test.


-- 
Eric Botcazou
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