[Bug rtl-optimization/55838] [4.6/4.7/4.8 Regression] ICE in extract_insn (unrecognizable insn) with -O -funroll-loops

["hjl.tools at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55838

--- Comment #10 from H.J. Lu <hjl.tools at gmail dot com> 2013-01-01 23:02:02 UTC ---
This patch avoids using (const_int 129 [0x81]) as step in QImode:

diff --git a/gcc/loop-iv.c b/gcc/loop-iv.c
index 50b7536..aafaae4 100644
--- a/gcc/loop-iv.c
+++ b/gcc/loop-iv.c
@@ -421,6 +421,8 @@ iv_constant (struct rtx_iv *iv, rtx cst, enum machine_mode
mode)
 static bool
 iv_subreg (struct rtx_iv *iv, enum machine_mode mode)
 {
+  rtx step;
+
   /* If iv is invariant, just calculate the new value.  */
   if (iv->step == const0_rtx
       && !iv->first_special)
@@ -442,13 +444,17 @@ iv_subreg (struct rtx_iv *iv, enum machine_mode mode)
   if (GET_MODE_BITSIZE (mode) > GET_MODE_BITSIZE (iv->mode))
     return false;

+  step = simplify_gen_binary (MULT, iv->extend_mode, iv->step, iv->mult);
+  if (trunc_int_for_mode (INTVAL (step), mode) != INTVAL (step))
+      return false;
+
   iv->extend = IV_UNKNOWN_EXTEND;
   iv->mode = mode;

   iv->base = simplify_gen_binary (PLUS, iv->extend_mode, iv->delta,
                   simplify_gen_binary (MULT, iv->extend_mode,
                                iv->base, iv->mult));
-  iv->step = simplify_gen_binary (MULT, iv->extend_mode, iv->step, iv->mult);
+  iv->step = step;
   iv->mult = const1_rtx;
   iv->delta = const0_rtx;
   iv->first_special = false;