GCC4.3.4 downside against GCC3.4.4 on mips?

[Andrew Haley]

On 05/25/2010 09:28 AM, Amker.Cheng wrote:
> Hi all,
>   I compared assembly files of a function compiled by GCC4.3.4 and GCC3.4.4.
> The function focuses on array computation and has no branch, or any
> loop structure,
> The command line is like "-march=mips32r2 -O3", and here is the
> instruction statics:
> 
>             total    : 1879 : 1534
>              addiu  :    6   :    6
>              addu  :  216  :  129
>               jr       :    1   :    1
>              lui      :    5    :    5
>               lw     :  396  :  353
>             madd  :   41   :    0
>             mfhi    :   80   :   80
>             mflo    :  121  :   86
>             move  :    0    :   21
>             mtlo   :   39   :    0
>              mul   :   85   :    0
>             mult   :   18   :   80
>            multu  :   64   :    0
>               or    :   80   :   80
>              sll     :   80  :   80
>              sra   :   79   :   47
>              srl    :   80   :   80
>             subu  :   80   :   80
>               sw   :  408  :  406
> 
> Considering there is no any branch or loop structure ,It seems result
> of GCC3.4.4
> is much better, since generating much less instructions.
> 
> secondly, GCC4.3.4 does consume less stack slots(1224 bytes against 1408).
> 
> So, any comments? Thanks in advance.

You're using -O3, which means "optimize as much as possible, don't worry
about code size".

Andrew.