On Tue, Jul 28, 2015 at 11:36 AM, Bin Cheng <[email protected]> wrote:
> Hi,
> Loop niter computes inaccurate bound information for different loops. This
> patch is to improve it by using loop initial condition in
> determine_value_range. Generally, loop niter is computed by subtracting
> start var from end var in loop exit condition. Moreover, loop bound is
> computed using value range information of both start and end variables.
> Basic idea of this patch is to check if loop initial condition implies more
> range information for both start/end variables. If yes, we refine range
> information and use that to compute loop bound.
> With this improvement, more accurate loop bound information is computed for
> test cases added by this patch.
+ c0 = fold_convert (type, c0);
+ c1 = fold_convert (type, c1);
+
+ if (operand_equal_p (var, c0, 0))
I believe if c0 is not already of type type operand-equal_p will never succeed.
(side-note: we should get rid of the GMP use, that's expensive and now we
have wide-int available which should do the trick as well)
+ /* Case of comparing with the bounds of the type. */
+ if (TYPE_MIN_VALUE (type)
+ && operand_equal_p (c1, TYPE_MIN_VALUE (type), 0))
+ cmp = GT_EXPR;
+ if (TYPE_MAX_VALUE (type)
+ && operand_equal_p (c1, TYPE_MAX_VALUE (type), 0))
+ cmp = LT_EXPR;
don't use TYPE_MIN/MAX_VALUE. Instead use the types precision
and all wide_int operations (see match.pd wi::max_value use).
+ else if (!operand_equal_p (var, varc0, 0))
+ goto end_2;
ick - goto. We need sth like a auto_mpz class with a destructor.
struct auto_mpz
{
auto_mpz () { mpz_init (m_val); }
~auto_mpz () { mpz_clear (m_val); }
mpz& operator() { return m_val; }
mpz m_val;
};
> Is it OK?
I see the code follows existing practice in niter analysis even though
my overall plan was to transition its copying of value-range related
optimizations to use VRP infrastructure.
I'm still ok with improving the existing code on the basis that I won't
get to that for GCC 6.
So - ok with the TYPE_MIN/MAX_VALUE change suggested above.
Refactoring with auto_mpz welcome.
Thanks,
RIchard.
> Thanks,
> bin
>
> 2015-07-28 Bin Cheng <[email protected]>
>
> * tree-ssa-loop-niter.c (refine_value_range_using_guard): New.
> (determine_value_range): Call refine_value_range_using_guard for
> each loop initial condition to improve value range.
>
> gcc/testsuite/ChangeLog
> 2015-07-28 Bin Cheng <[email protected]>
>
> * gcc.dg/tree-ssa/loop-bound-1.c: New test.
> * gcc.dg/tree-ssa/loop-bound-3.c: New test.
> * gcc.dg/tree-ssa/loop-bound-5.c: New test.
