[Bug rtl-optimization/35281] [4.3/4.4 Regression] multiply with 0 generated for 64*32->64

[ubizjak at gmail dot com]

------- 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