------- Comment #9 from bergner at gcc dot gnu dot org 2010-02-23 21:57 -------
This is a generic reload bug. With this test case and options, we have the
following instructions just before IRA:
(insn 203 2 213 2 (set (reg/f:DI 256 [ vect_pk.44 ])
(plus:DI (reg/f:DI 255)
(const_int 16 [0x10]))) 83 {*adddi3_internal1} (expr_list:REG_EQUAL
(const:DI (plus:DI (symbol_ref:DI ("*.LANCHOR2") [flags 0x182])
(const_int 16 [0x10])))
(nil)))
...
(insn 21 214 25 2 pr42431.f:27 (set (reg:DI 270)
(const_int 16 [0x10])) 371 {*movdi_internal64} (nil))
...
(insn 20 17 23 3 pr42431.f:27 (set (mem:V4SI (reg/f:DI 256 [ vect_pk.44 ]) [4
S16 A128])
(reg:V4SI 269)) 926 {*altivec_movv4si} (expr_list:REG_EQUAL
(const_vector:V4SI [
(const_int 0 [0x0])
(const_int 0 [0x0])
(const_int 0 [0x0])
(const_int 0 [0x0])
])
(nil)))
(insn 23 20 232 3 pr42431.f:27 (set (mem:V4SI (plus:DI (reg/f:DI 256 [
vect_pk.44 ])
(reg:DI 270)) [4 S16 A128])
(reg:V4SI 269)) 926 {*altivec_movv4si} (expr_list:REG_EQUAL
(const_vector:V4SI [
(const_int 0 [0x0])
(const_int 0 [0x0])
(const_int 0 [0x0])
(const_int 0 [0x0])
])
(nil)))
Both r256 and r270 are marked for spilling. This leads to two chained reloads:
(const:DI (plus:DI (symbol_ref:DI ("*.LANCHOR2") [flags 0x182]) (const_int 16
[0x10])))
and
(const_int 16 [0x10])
With these chained reloads, we eventually drop into
gen_reload_chain_without_interm_reg_p(). This function does a copy_rtx() to
create a scratch rtx it can modify to run some tests on and then throw away.
The bug is that copy_rtx() simply returns the passed in rtx pointer for CONST
rtxs, so we end up modifying the program's real rtl rather than some scratch
rtl. Since we cannot execute the copy_rtx/substitue statements without causing
problems, I'm testing the patch below to see if it fixes the
problem...although, if there are CONSTs buried deep within the reload rtx, we
probably could still end up with a similar problem on a different test case.
Comments anyone?
Index: reload1.c
===================================================================
--- reload1.c (revision 156816)
+++ reload1.c (working copy)
@@ -5221,6 +5221,10 @@
r1 = r2;
r2 = n;
}
+
+ if (GET_CODE (rld[r1].in) == CONST)
+ return true;
+
gcc_assert (reg_mentioned_p (rld[r2].in, rld[r1].in));
regno = rld[r1].regno >= 0 ? rld[r1].regno : rld[r2].regno;
gcc_assert (regno >= 0);
--
bergner at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |vmakarov at gcc dot gnu dot
| |org
Component|target |middle-end
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42431
