[patch] Minor adjustment to gimplify_addr_expr

[Eric Botcazou]

Hi,

this is the regression of ACATS c37213k at -O2 with an upcoming change in
the front-end of the Ada compiler:

eric@polaris:~/gnat/gnat-head/native> gcc/gnat1 -quiet c37213k.adb -I 
/home/eric/gnat/bugs/support -O2 
+===========================GNAT BUG DETECTED==============================+
| Pro 7.4.0w (20151014-60) (x86_64-suse-linux) GCC error:                  |
| tree check: expected class 'expression', have              |
|     'exceptional' (ssa_name) in tree_operand_check, at tree.h:3431|
| Error detected around c37213k.adb:95:37

It's recompute_tree_invariant_for_addr_expr receiving an SSA_NAME instead of
an ADDR_EXPR when called from gimplify_addr_expr.  The sequence is as follows:
we start with this GIMPLE statement:

  *R.43_60 = c37213k.B_1.B_6.proc6.B_4.B_5.value (); [static-chain: &FRAME.60] 
[return slot optimization]

Then IPA clones the function and turns the statement into:

  MEM[(struct c37213k__B_1__B_6__proc6__B_4__nrec *)R.43_46] = 
c37213k.B_1.B_6.proc6.B_4.B_5.value (); [static-chain: &FRAME.60] [return slot 
optimization]

The 'value' function has been NRVed and contains:

  .builtin_memcpy (&<retval>, _9, _10);

and gets inlined so the above statement is rewritten into:

.builtin_memcpy (&MEM[(struct c37213k__B_1__B_6__proc6__B_4__nrec *)R.43_46], 
_174, _175);

so gimplify_addr_expr is invoked on:

  &MEM[(struct c37213k__B_1__B_6__proc6__B_4__nrec *)R.43_46]

and gets confused because it doesn't see that it's just R.43_46 (it would have
seen it if the original INDIRECT_REF was still present in lieu of MEM_REF).

Hence the attached fixlet.  Tested on x86_64-suse-linux, OK for the mainline?


2015-10-14  Eric Botcazou  <ebotca...@adacore.com>

        * gimplify.c (gimplify_addr_expr) <MEM_REF>: New case.

-- 
Eric Botcazou
Index: gimplify.c
===================================================================
--- gimplify.c	(revision 228794)
+++ gimplify.c	(working copy)
@@ -4984,6 +4984,12 @@ gimplify_addr_expr (tree *expr_p, gimple
       ret = GS_OK;
       break;
 
+    case MEM_REF:
+      if (integer_zerop (TREE_OPERAND (op0, 1)))
+	goto do_indirect_ref;
+
+      /* ... fall through ... */
+
     default:
       /* If we see a call to a declared builtin or see its address
 	 being taken (we can unify those cases here) then we can mark