[PATCH 2/2] rs6000: tune loop size for cunroll at O2

[Jiufu Guo via Gcc-patches]

Hi,

This patch check the size of a loop to be unrolled/peeled completely,
and set the limits to a number (24).  This prevents large loop from
being unrolled, then avoid binary size increasing, and this limit keeps
performance.

Bootstrap&regtest pass on powerpc64le, ok for trunk?

Jiufu

---
 gcc/config/rs6000/rs6000.c | 19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/gcc/config/rs6000/rs6000.c b/gcc/config/rs6000/rs6000.c
index a1a3f9cb583..f3abb92d046 100644
--- a/gcc/config/rs6000/rs6000.c
+++ b/gcc/config/rs6000/rs6000.c
@@ -5142,6 +5142,22 @@ rs6000_loop_unroll_adjust (unsigned nunroll, struct loop 
*loop)
   return nunroll;
 }
 
+/* Count the number of statements in LOOP.  */
+
+static int
+num_stmt_in_loop (class loop *loop)
+{
+  int res = 0;
+  basic_block *bbs = get_loop_body (loop);
+  for (unsigned i = 0; i < loop->num_nodes; i++)
+    for (gimple_stmt_iterator bsi = gsi_start_bb (bbs[i]); !gsi_end_p (bsi);
+        gsi_next (&bsi))
+      if (!is_gimple_debug (gsi_stmt (bsi)))
+       res++;
+
+  return res;
+}
+
 /* Implement targetm.loop_allow_unroll_completely_peel.  */
 
 static bool
@@ -5151,7 +5167,8 @@ rs6000_loop_allow_unroll_completely_peel (HOST_WIDE_INT 
maxiter, tree niter,
   if (unroll_only_small_loops && optimize == 2)
     {
       if (maxiter >= 4
-         && !(TREE_CODE (niter) == INTEGER_CST && single_exit (loop)))
+         && !(TREE_CODE (niter) == INTEGER_CST && num_stmt_in_loop (loop) < 24
+              && single_exit (loop)))
        return false;
     }
 
-- 
2.17.1