[PATCH] Optimize certain end of loop conditions into min/max operation

[Michael Collison]

This patch is designed to optimize end of loop conditions involving of 
the form
 i < x && i < y into i < min (x, y). Loop condition involving '>' are 
handled similarly using max(x,y).
As an example:

#define N 1024
int  a[N], b[N], c[N];

void add (unsignedint  m, unsignedint  n)
{
  unsignedint  i, bound = (m < n) ? m : n;
  for  (i = 0; i < m && i < n; ++i)
    a[i] = b[i] + c[i];
}


Performed bootstrap and make check on: x86_64_unknown-linux-gnu, 
arm-linux-gnueabihf, and aarch64-linux-gnu.
Okay for trunk?

2015-07-24  Michael Collison  <michael.colli...@linaro.org>
                    Andrew Pinski <andrew.pin...@caviumnetworks.com>

                * match.pd ((x < y) && (x < z) -> x < min (y,z),
                (x > y) and (x > z) -> x > max (y,z))

diff --git a/gcc/match.pd b/gcc/match.pd
index 5e8fd32..8691710 100644
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -1793,3 +1793,17 @@ along with GCC; see the file COPYING3.  If not see
     (convert (bit_and (op (convert:utype @0) (convert:utype @1))
               (convert:utype @4)))))))

+
+/* Transform (@0 < @1 and @0 < @2) to use min */
+(for op (lt le)
+(simplify
+(bit_and:c (op @0 @1) (op @0 @2))
+(if (INTEGRAL_TYPE_P (TREE_TYPE (@0)))
+(op @0 (min @1 @2)))))
+
+/* Transform (@0 > @1 and @0 > @2) to use max */
+(for op (gt ge)
+(simplify
+(bit_and:c (op @0 @1) (op @0 @2))
+(if (INTEGRAL_TYPE_P (TREE_TYPE (@0)))
+(op @0 (max @1 @2)))))
--

--
Michael Collison
Linaro Toolchain Working Group
michael.colli...@linaro.org