[patch] Fix ICE on function [not] returning variable size

[Eric Botcazou]

Hi,

this fixes an ICE on a function returning a variable-sized record type but 
discovered to be no-return by the optimizer.  In this case, the LHS of the 
GIMPLE call statement is removed so the RTL expander attempts to allocate a 
temporary and fails:

eric@polaris:~/build/gcc/native> gcc/gnat1 -quiet varsize_return2.ads -O
+===========================GNAT BUG DETECTED==============================+
| 6.0.0 20150531 (experimental) [trunk revision 223897] (x86_64-suse-linux) 
GCC error:|
| in assign_stack_temp_for_type, at function.c:793        

because it too cannot create temporaries of variable size.

The attached patch simply preserves the LHS throughout the GIMPLE pipeline.
It also simplifies the relevant test in gimplify_modify_expr_rhs, which was 
overly broad.

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


2015-06-01  Eric Botcazou  <ebotcazou@adacore.com>

	* gimplify.c (gimplify_modify_expr_rhs): Use simple test on the size.
	* cgraph.c (cgraph_redirect_edge_call_stmt_to_callee): Do not remove
	the LHS of a no-return call if its type has variable size.
	* tree-cfgcleanup.c (fixup_noreturn_call): Likewise.
	* tree-cfg.c (verify_gimple_call): Accept these no-return calls.


2015-06-01  Eric Botcazou  <ebotcazou@adacore.com>

	* gnat.dg/specs/varsize_return2.ads: New test.
	* gnat.dg/specs/varsize_return2_pkg.ad[sb]: New helper.


-- 
Eric Botcazou
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