[Bug middle-end/33348] [4.3 Regression] gfortran.dg/g77/19990826-3.f fails at -O1

[rakdver at kam dot mff dot cuni dot cz]

------- Comment #4 from rakdver at kam dot mff dot cuni dot cz  2007-09-16 22:07 -------
Subject: Re:  [4.3 Regression] gfortran.dg/g77/19990826-3.f fails at -O1

> What happens in this testcase is (mis)behaviour of invariant code motion.
> On instruction:
> (set (mem/c/i:SI (plus:DI (reg/f:DI 113 sfp)
>             (const_int 80 [0x50])) [3 S4 A32])
>     (fix:SI (reg:DF 135)))
> 
> the invariant code is trying to replace the write->load pair, however the
> truncsfdf2 expander is expanding fix from reg to reg will offload the value to
> memory again, so we are replacing load by:
> 
> (insn 44 0 45 (parallel [
>             (set (mem/c/i:SI (plus:DI (reg/f:DI 113 sfp)
>                         (const_int 84 [0x54])) [3 S4 A32])
>                 (fix:SI (reg:DF 135)))
>             (clobber (reg:DI 138))
>         ]) -1 (nil))
> 
> (insn 45 44 46 (set (reg:SI 137)
>         (mem/c/i:SI (plus:DI (reg/f:DI 113 sfp)
>                 (const_int 84 [0x54])) [3 S4 A32])) -1 (expr_list:REG_EQUAL
> (fix:SI (reg:DF 135))
>         (nil)))
> 
> (insn 46 45 0 (set (reg:SI 136)
>         (reg:SI 137)) -1 (nil))
> 
> This is not very sane transformation at all IMO.

Actually, it may make some sense -- the newly generated memory store &
load are outside of the loop; so the code inside the loop is simplified,
and in some cases we might even avoid memory accesses inside the loop.
Nevertheless, force_operand in move_invariant_reg causes other problems
as well, so I guess I will remove this code.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33348