[Bug rtl-optimization/50904] Induct benchmark of polyhedron slows down when -fno-protect-parens is enabled by -Ofast.

[venkataramanan.kumar.gnu at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50904

--- Comment #7 from Venkataramanan Kumar <venkataramanan.kumar.gnu at gmail dot com> 2011-11-02 05:50:44 UTC ---
(In reply to comment #6)
> > I don't see why RTL invariant motion should move the one variant but not
> > the other.  Of course this also shows that we should, after loop unrolling
> > on the tree level, also perform loop invariant motion again ...
> The problem seems to be in RTL PRE, which hoists simple loads but not loads
> that are wrapped up in a PLUS or a MINUS.  Even with -fprotect-parens, load
> hoisting opportunities are lost because of this.

You mean to say PRE hosits the when expression of this pattern.

(Snip)
(insn 536 533 537 14 (set (reg:V2DF 1172 [ MEM[(real(kind=8)[9] *)&y2gauss] ])
        (mem/c:V2DF (symbol_ref:DI ("y2gauss.2335") [flags 0x2]  <var_decl
0x2aaaabb09dc0 y2gauss>) [8 MEM[(real(kind=8)[9] *)&y2gauss]+0 S16 A256]))
induct2.f90:1662 1102 {*movv2df_internal}
(Snip)


But not of this pattern.

(Snip)
(insn 526 525 527 14 (set (reg:V2DF 1123)
        (plus:V2DF (reg:V2DF 1124)
            (mem/c:V2DF (symbol_ref:DI ("y2gauss.2335") [flags 0x2]  <var_decl
0x2aaaabb09dc0 y2gauss>) [8 MEM[(real(kind=8)[9] *)&y2gauss]+0 S16 A256])))
../induct2.f90:1662 1130 {*addv2df3}
(Snip)