Dump a diagnostic info when the insn-to-mem ratio is too small.

[pf3gnuchains/gcc-fork.git] / gcc / tree-ssa-loop-prefetch.c

diff --git a/gcc/tree-ssa-loop-prefetch.c b/gcc/tree-ssa-loop-prefetch.c
index 3377eeb..6f87988 100644 (file)
--- a/gcc/tree-ssa-loop-prefetch.c
+++ b/gcc/tree-ssa-loop-prefetch.c
@@ -1551,7 +1551,13 @@ is_loop_prefetching_profitable (unsigned ahead, HOST_WIDE_INT est_niter,
   insn_to_mem_ratio = ninsns / mem_ref_count;
 
   if (insn_to_mem_ratio < PREFETCH_MIN_INSN_TO_MEM_RATIO)
-    return false;
+    {
+      if (dump_file && (dump_flags & TDF_DETAILS))
+        fprintf (dump_file,
+                "Not prefetching -- instruction to memory reference ratio (%d) too small\n",
+                insn_to_mem_ratio);
+      return false;
+    }
 
   /* Profitability of prefetching is highly dependent on the trip count.
      For a given AHEAD distance, the first AHEAD iterations do not benefit