[PATCH][PR65818][bootstrap,hppa] Return side-effect free result in gimplify_va_arg_internal

[Tom de Vries <Tom_deVries at mentor dot com>]

Hi,

this patch fixes PR65818, and hppa bootstrap.

When compiling gcc/libiberty/vprintf-support.c, the following va_arg is compiled:
...
 (void) __builtin_va_arg(ap, double);
...

This results in the following ifn_va_arg at gimple level, with a NULL_TREE lhs:
...
  VA_ARG (&ap, 0B);
...

We start expanding the ifn_va_arg in expand_ifn_va_arg_1 by calling 
gimplify_va_arg_internal:
...
        expr = gimplify_va_arg_internal (ap, type, gimple_location (stmt),
                                         &pre, &post);
...

Subsequently, because the lhs is NULL_TREE, we skip generating the assign to the 
lhs:
...
	lhs = gimple_call_lhs (stmt);
	if (lhs != NULL_TREE)
	  {
	    gcc_assert (useless_type_conversion_p (TREE_TYPE (lhs), type));

	    if (gimple_call_num_args (stmt) == 3)
	      {
		/* We've transported the size of with WITH_SIZE_EXPR here as
		   the 3rd argument of the internal fn call.  Now reinstate
		   it.  */
		tree size = gimple_call_arg (stmt, 2);
		expr = build2 (WITH_SIZE_EXPR, TREE_TYPE (expr), expr, size);
	      }

	    /* We use gimplify_assign here, rather than gimple_build_assign,
	       because gimple_assign knows how to deal with variable-sized
	       types.  */
	    gimplify_assign (lhs, expr, &pre);
	  }
...

We assume here that any side-effects related to updating ap have been generated 
into pre/post by gimplify_va_arg_internal, and that it's safe to ignore expr.

Turns out, that's not the case for hppa. The target hook 
hppa_gimplify_va_arg_expr (called from gimplify_va_arg_internal) returns an 
expression that still contains a side-effect:
...
*(double *) (ap = ap + 4294967288 & 4294967288B)
...

This patch fixes that by gimplifying the address expression of the mem-ref 
returned by the target hook (borrowing code from gimplify_expr, case MEM_REF).

Bootstrapped and reg-tested on x86_64.

Bootstrapped and reg-tested on hppa2.0w-hp-hpux11.11.

OK for trunk?

Thanks,
- Tom

Return side-effect free result in gimplify_va_arg_internal

2015-04-22  Tom de Vries  <tom@codesourcery.com>

	PR tree-optimization/65818
	* gimplify.c (gimplify_va_arg_internal): Ensure that only side-effect
	free values are returned.
---
 gcc/gimplify.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/gcc/gimplify.c b/gcc/gimplify.c
index c68bd47..fe54e53 100644
--- a/gcc/gimplify.c
+++ b/gcc/gimplify.c
@@ -9352,7 +9352,12 @@ gimplify_va_arg_internal (tree valist, tree type, location_t loc,
   else
     gimplify_expr (&valist, pre_p, post_p, is_gimple_min_lval, fb_lvalue);
 
-  return targetm.gimplify_va_arg_expr (valist, type, pre_p, post_p);
+  tree expr = targetm.gimplify_va_arg_expr (valist, type, pre_p, post_p);
+  gcc_assert (TREE_CODE (expr) == MEM_REF);
+  if (!is_gimple_mem_ref_addr (TREE_OPERAND (expr, 0)))
+    gimplify_expr (&TREE_OPERAND (expr, 0), pre_p, post_p,
+		   is_gimple_mem_ref_addr, fb_rvalue);
+  return expr;
 }
 
 /* Gimplify __builtin_va_arg, aka VA_ARG_EXPR, which is not really a
-- 
1.9.1