[PATCH] Fix PR middle-end/17746

[Eric Botcazou]

Hello,

This is the first of the two ICEs that prevent the Ada runtime from building 
on SPARC.  The compiler aborts in expand_expr_addr_expr_1 on

  /* We must have made progress.  */
  gcc_assert (inner != exp);


expand_expr_addr_expr_1 is passed the following tree:

  COMPONENT_REF
    VIEW_CONVERT_EXPR <record_type1 ... align-ok>
      INDIRECT_REF <record_type2>
        VAR_DECL <pointer_type <record_type2>>

record_type1 is a derived type of record_type2 and the expression is a 
dereference through a polymorphic access type (pointer).

expand_expr_addr_expr_1 essentially uses get_inner_reference to recurse until 
it finds an interesting node, here the INDIRECT_REF node.  This works fine on 
x86 but not always on SPARC because get_inner_reference may refuse to look 
through the VIEW_CONVERT_EXPR because of

      /* We can go inside most conversions: all NON_VALUE_EXPRs, all normal
	 conversions that don't change the mode, and all view conversions
	 except those that need to "step up" the alignment.  */
      else if (TREE_CODE (exp) != NON_LVALUE_EXPR
	       && ! (TREE_CODE (exp) == VIEW_CONVERT_EXPR
		     && ! ((TYPE_ALIGN (TREE_TYPE (exp))
			    > TYPE_ALIGN (TREE_TYPE (TREE_OPERAND (exp, 0))))
			   && STRICT_ALIGNMENT
			   && (TYPE_ALIGN (TREE_TYPE (TREE_OPERAND (exp, 0)))
			       < BIGGEST_ALIGNMENT)
			   && (TYPE_ALIGN_OK (TREE_TYPE (exp))
			       || TYPE_ALIGN_OK (TREE_TYPE
						 (TREE_OPERAND (exp, 0))))))
	       && ! ((TREE_CODE (exp) == NOP_EXPR
		      || TREE_CODE (exp) == CONVERT_EXPR)
		     && (TYPE_MODE (TREE_TYPE (exp))
			 == TYPE_MODE (TREE_TYPE (TREE_OPERAND (exp, 0))))))
	break;

The key is of course STRICT_ALIGNMENT here.


The proposed fix is to teach expand_expr_addr_expr_1 to look itself through 
the VIEW_CONVERT_EXPR nodes that "step up" the alignment, but only if they 
carry the TYPE_ALIGN_OK flag.  The rationale is that these VIEW_CONVERT_EXPR 
nodes will not cause any temporary to be generated so they are noop when it 
comes to take the address.

Bootstrapped/regtested on sparc64-sun-solaris2.9 and sparc-sun-solaris2.8, 
with upcoming patch for PR middle-end/17793.


2004-10-19  Eric Botcazou  <ebotcazou@libertysurf.fr>

	PR middle-end/17746
	* expr.c (expand_expr_addr_expr_1): Look through VIEW_CONVERT_EXPR
	nodes that "step up" the alignment if the object is already sufficiently
 	aligned.


-- 
Eric Botcazou
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