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[Bug rtl-optimization/35281] [4.3/4.4 Regression] multiply with 0 generated for 64*32->64
- From: "ubizjak at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 5 Mar 2008 10:32:31 -0000
- Subject: [Bug rtl-optimization/35281] [4.3/4.4 Regression] multiply with 0 generated for 64*32->64
- References: <bug-35281-10175@http.gcc.gnu.org/bugzilla/>
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
------- Comment #6 from ubizjak at gmail dot com 2008-03-05 10:32 -------
4.2 figures out in cse1 pass that:
(insn 9 8 10 2 (parallel [
(set (reg:DI 60 [ b ])
(zero_extend:DI (mem/c/i:SI (symbol_ref:SI ("b") <var_decl
0xb7caf108 b>) [3 b+0 S4 A32])))
(clobber (reg:CC 17 flags))
]) 79 {zero_extendsidi2_32} (nil)
(nil))
...
(insn 11 10 12 2 (parallel [
(set (reg:SI 61)
(mult:SI (reg:SI 62 [ a ])
(subreg:SI (reg:DI 60 [ b ]) 4)))
(clobber (reg:CC 17 flags))
]) 182 {*mulsi3_1} (nil)
(nil))
can simply be substituted with:
(insn 11 9 12 2 (set (reg:SI 61)
(const_int 0 [0x0])) 34 {*movsi_1} (nil)
(nil))
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35281