RE: [avr-gcc-list] Can someone benchmark this option please

[Weddington, Eric]

> -----Original Message-----
> From: 
> address@hidden 
> [mailto:address@hidden
> org] On Behalf Of Andy H
> Sent: Tuesday, July 22, 2008 6:40 PM
> To: AVR-GCC
> Subject: [avr-gcc-list] Can someone benchmark this option please
> 
> Hi,
> 
> I have noted problem where gcc is optimizing if-then-else 
> constructs - 
> with disastrous results. For example:
> 
> if (a  >= 0)
>   return 8;
> else
>  return 0;
> 
> (This is now reported as bug.)
> 
> Can folks try the following gcc option
> 
>  -fno-if-conversion
> 
> on their own code at -Os optimization, and see if this produce 
> better/worse or same code? This will help figure if the whole pass 
> should be skipped - or whether it still contains useful optimizations.
> 

Hi Andy,

I tried it on the BC100 Kit code for gcc, which uses these options:

-mmcu=attiny861
-gdwarf-2 
-Os 
-funsigned-char 
-funsigned-bitfields 
-fpack-struct 
-fshort-enums 
-Wall 
-Wstrict-prototypes 
-std=gnu99 
-ffunction-sections 
-fno-inline-small-functions 
-fno-split-wide-types

When I added -fno-if-conversion, there was no change in code size: 5588 bytes.