------- Comment #6 from rguenth at gcc dot gnu dot org 2010-01-08 15:00 -------
Hm, actually what is wrong is the evolution of l_2_18:
(scalar = l_2_18)
(scalar_evolution = {255, +, 0x0ffffffff}_1))
that of l_2_10 is correct:
(scalar = l_2_10)
(scalar_evolution = (unsigned int) {254, +, 255}_1))
<bb 3>:
# l_2_18 = PHI <l_2_10(4), 0x0ffffffff(2)>
# prephitmp.10_25 = PHI <g_3.2_7(4), pretmp.9_24(2)>
# ivtmp.19_37 = PHI <ivtmp.19_29(4), 255(2)>
D.1960_3 = (short unsigned int) l_2_18;
g_3.1_5 = (short unsigned int) prephitmp.10_25;
D.1963_6 = D.1960_3 | g_3.1_5;
g_3.2_7 = (short int) D.1963_6;
g_3_lsm.18_11 = g_3.2_7;
D.1965_8 = (unsigned char) l_2_18;
D.1966_9 = D.1965_8 + 255;
l_2_10 = (unsigned int) D.1966_9;
ivtmp.19_29 = ivtmp.19_37 - 1;
if (ivtmp.19_29 != 0)
goto <bb 4>;
else
goto <bb 5>;
<bb 4>:
goto <bb 3>;
Thus we need to verify we maintain the correct initial condition only?
Like for example with
Index: tree-scalar-evolution.c
===================================================================
--- tree-scalar-evolution.c (revision 155732)
+++ tree-scalar-evolution.c (working copy)
@@ -1642,6 +1642,15 @@ interpret_loop_phi (struct loop *loop, g
init_cond = analyze_initial_condition (loop_phi_node);
res = analyze_evolution_in_loop (loop_phi_node, init_cond);
+ /* Verify we maintained the correct initial condition throughout
+ possible conversions in the SSA chain. */
+ if (res != chrec_dont_know)
+ {
+ tree new_init = initial_condition (res);
+ if (!operand_equal_p (init_cond, new_init, 0))
+ return chrec_dont_know;
+ }
+
return res;
}
Maybe too strict in case the returned chrec is wrapped in a conversion
operation itself (no idea if that ever happens - at least initial_condition
doesn't seem to deal with that during recursion either).
I'm going to test that patch.
--
rguenth at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
AssignedTo|unassigned at gcc dot gnu |rguenth at gcc dot gnu dot
|dot org |org
Status|NEW |ASSIGNED
Last reconfirmed|2009-12-26 20:00:19 |2010-01-08 15:00:44
date| |
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42512
