Re: Simplifying Gimple Generation

[Xinliang David Li <davidxl at google dot com>]

On Fri, Nov 16, 2012 at 5:13 AM, Diego Novillo <dnovillo@google.com> wrote:
> On Thu, Nov 15, 2012 at 2:31 AM, Xinliang David Li <davidxl@google.com> wrote:
>
>>> ssa_stmt t = q.stmt (NE_EXPR, shadow, 0);
>>> ssa_stmt a = q.stmt (BIT_AND_EXPR, base_addr, 7);
>>> ssa_stmt b = q.stmt (shadow_type, a);
>>> ssa_stmt c = q.stmt (PLUS_EXPR, b, offset);
>>> ssa_stmt d = q.stmt (GE_EXPR, c, shadow);
>>> ssa_stmt e = q.stmt (BIT_AND_EXPR, t, d);
>>
>>
>> seq_seq::stmt(...) sounds like a getter interface, not a creator.
>
> Sure. They could be named new_stmt() or build_stmt() or something similar.
>
>> x = q.new_assignment (...);
>> x = q.new_call (..);
>> x.add_arg(..);
>> x = q.new_icall (..);
>>
>> l1 = q.new_label ("xx");
>> l2 = q.new_label ("xxx");
>> join_l = q.new_label ("...");
>>
>> x = new_if_then_else (cond, l1, l2, join_l);
>> q.insert_label (l1);
>> q.new_assignment (...);
>> q.insert_label(l2);
>> ...
>> q.insert_label(join_l);
>> q.close_if_then_else(x);
>
> What I was thinking for if_then_else constructs was something along
> the lines of:
>
> stmt_seq then_body(s1);
> then_body.add_stmt(s2);
>
> stmt_seq else_body(r1);
> else_body.add_stmt(r2);
> stmt if_then_else(cond, then_body, else_body);


That looks good. The interface should also allow user to specify
branch prob. It is probably useful to consider support creating
if-then-else with multiple conditions with short circuit  semantics.
The interface should look very similar.

thanks,

David


>
> You can then take 'if_then_else' and insert it inside a basic block or
> an edge.  When that happens, the builder takes care of the block/edge
> splitting for you.
>
>>> .. The statement result type is that of the arguments.
>>>
>>> .. The type of integral constant arguments is that of the other
>>> argument.  (Which implies that only one argument can be constant.)
>>>
>>> .. The 'stmt' method handles linking the statement into the sequence.
>>>
>>> .. The 'set_location' method iterates over all statements.
>>>
>>> There will be another class of builders for generating GIMPLE
>>> in normal form (gimple_stmt).  We expect that this will mostly
>>> affect all transformations that need to generate new expressions
>>> and statements, like instrumentation passes.
>>
>> What are the uses of the raw forms?
>
> Sorry, what are these "raw forms" that you refer to?
>
>>> tree inttype = build_nonstandard_integer_type (POINTER_SIZE, 1);
>>> record_builder rec ("__asan_global");
>>> rec.field ("__beg", const_ptr_type_node);
>>> rec.field ("__size", inttype);
>>> rec.field ("__size_with_redzone", inttype);
>>> rec.field ("__name", const_ptr_type_node);
>>> rec.field ("__has_dynamic_init", inttype);
>>> rec.finish ();
>>> tree ret = rec.as_tree ();
>>
>> Again, something like new_field or add_field is more intuitive.
>
> Sure.
>
>
> Diego.