On 03/06/2015 02:01 PM, Jason Merrill wrote:
On 03/06/2015 05:01 PM, Jason Merrill wrote:
On 03/06/2015 04:54 PM, Aldy Hernandez wrote:
But doesn't this still involve a MODIFY_EXPR, i.e. return retval =
D.2349?
If I understand you correct, no.
gimplify_return_expr creates a new temporary and uses that instead of
<retval>:
else if (gimplify_ctxp->return_temp)
result = gimplify_ctxp->return_temp;
else
{
result = create_tmp_reg (TREE_TYPE (result_decl));
...
}
...
...
/* Smash the lhs of the MODIFY_EXPR to the temporary we plan to use.
Then gimplify the whole thing. */
if (result != result_decl)
TREE_OPERAND (ret_expr, 0) = result;
Sounds like ret_expr is a MODIFY_EXPR.
Oh, but with the wrong lhs, I see.
I know you want to reuse the MODIFY_EXPR case in cp_gimplify_expr, but
after playing around with it, I think it requires too much special
casing to make it clean.
For instance, the MODIFY_EXPR case returns the RHS of expression which
is the opposite of what we want. For this:
return retval = <obj>
...the MODIFY_EXPR case would build a COMPOUND_EXPR with "return
<<<retval, <obj>>>>", which would return <obj>, not retval. And what we
probably want is a statement list with:
<evaluation of obj>
return retval
Also, the actual case we're dealing with here is a bit more
complicated, as it involves a COMPOUND_EXPR in the RHS, which we'd have
to adapt MODIFY_EXPR to handle:
return retval = <<<TARGET_EXPR, D.9999>>
IMHO, adding a special case for all this is a lot messier than what I
originally suggested.