[patch] Fix checking failure in IPA-SRA

[Eric Botcazou]

Hi,

this is a regression present on the mainline and 10 branch: on the one hand, 
IPA-SRA does *not* disqualify accesses with zero size but, on the other hand, 
it checks that accesses present in the tree have a (strictly) positive size,
thus trivially yielding an ICE, for example on the attached Ada testcase.

The attached fix relaxes the check, OK for mainline and 10 branch?


2020-12-03  Eric Botcazou  <ebotcazou@adacore.com>

	* ipa-sra.c (verify_access_tree_1): Relax assertion on the size.


2020-12-03  Eric Botcazou  <ebotcazou@adacore.com>

	* gnat.dg/opt91.ad[sb]: New test.
	* gnat.dg/opt91_pkg.ad[sb]: New helper.

-- 
Eric Botcazou
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