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[Bug target/27856] With -Os, loading a constant to a register can use another register
- From: "pinskia at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 1 Jun 2006 17:21:06 -0000
- Subject: [Bug target/27856] With -Os, loading a constant to a register can use another register
- References: <bug-27856-1034@http.gcc.gnu.org/bugzilla/>
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
------- Comment #1 from pinskia at gcc dot gnu dot org 2006-06-01 17:21 -------
Confirmed, this is a RA issue.
Before register allocation:
(insn:HI 10 7 11 2 (set (reg:SI 63)
(const_int 3 [0x3])) 34 {*movsi_1} (nil)
(expr_list:REG_EQUIV (const_int 3 [0x3])
(nil)))
(insn:HI 11 10 15 2 (parallel [
(set (reg:SI 61)
(udiv:SI (reg/v:SI 59 [ val ])
(reg:SI 63)))
(set (reg:SI 62)
(umod:SI (reg/v:SI 59 [ val ])
(reg:SI 63)))
(clobber (reg:CC 17 flags))
]) 197 {udivmodsi4} (insn_list:REG_DEP_TRUE 6 (insn_list:REG_DEP_TRUE
10 (nil)))
(expr_list:REG_UNUSED (reg:CC 17 flags)
(expr_list:REG_UNUSED (reg:SI 62)
(expr_list:REG_DEAD (reg/v:SI 59 [ val ])
(expr_list:REG_DEAD (reg:SI 63)
(expr_list:REG_UNUSED (reg:CC 17 flags)
(expr_list:REG_UNUSED (reg:SI 62)
(nil))))))))
-----------
After:
(insn:HI 10 7 30 2 (set (reg:SI 1 dx [63])
(const_int 3 [0x3])) 34 {*movsi_1} (nil)
(expr_list:REG_EQUIV (const_int 3 [0x3])
(nil)))
(insn 30 10 11 2 (set (reg:SI 2 cx)
(reg:SI 1 dx [63])) 34 {*movsi_1} (nil)
(nil))
(insn:HI 11 30 15 2 (parallel [
(set (reg:SI 0 ax [61])
(udiv:SI (reg/v:SI 0 ax [orig:59 val ] [59])
(reg:SI 2 cx)))
(set (reg:SI 1 dx [62])
(umod:SI (reg/v:SI 0 ax [orig:59 val ] [59])
(reg:SI 2 cx)))
(clobber (reg:CC 17 flags))
]) 197 {udivmodsi4} (insn_list:REG_DEP_TRUE 6 (insn_list:REG_DEP_TRUE
10 (nil)))
(nil))
--
pinskia at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |NEW
Ever Confirmed|0 |1
Keywords| |ra
Last reconfirmed|0000-00-00 00:00:00 |2006-06-01 17:21:06
date| |
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=27856