[Bug target/33604] [4.3/4.4 Regression] Revision 119502 causes significantly slower results with 4.3/4.4 compared to 4.2

["amonakov at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>]

------- Comment #43 from amonakov at gcc dot gnu dot org  2008-08-29 13:12 -------
Checking original testcase times on x86_64 prescott with gentoo 4.2, 4.3 and
today's trunk:
2.960s    g++-4.2.4 (GCC) 4.2.4 (Gentoo 4.2.4 p1.0)
2.916s    g++-4.3.1 (Gentoo 4.3.1-r1 p1.1) 4.3.1
3.993s    g++ (GCC) 4.4.0 20080829 (experimental)
2.796s    g++ (GCC) 4.4.0 20080829 (experimental) with --param
max-inline-insns-auto=126

So I believe lack of inlining is the biggest 4.4's problem. We do not inline
3x3 matrix multiplication in benchmark loop.

While looking at it I found that einline2 dump does not always show the reason
for not inlining. I would like to propose the following patch:

--- a/gcc/ipa-inline.c
+++ b/gcc/ipa-inline.c
@@ -1494,6 +1494,8 @@ cgraph_decide_inlining_incrementally (struct cgraph_node
*node,
          }
        if (cgraph_default_inline_p (e->callee, &failed_reason))
          inlined |= try_inline (e, mode, depth);
+       else if (dump_file)
+         fprintf (dump_file, "Not inlining: %s.\n", failed_reason);
       }
   node->aux = (void *)(size_t) old_mode;
   return inlined;


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33604