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RE: [avr-gcc-list] Can someone benchmark this option please
From: |
Weddington, Eric |
Subject: |
RE: [avr-gcc-list] Can someone benchmark this option please |
Date: |
Wed, 23 Jul 2008 11:17:30 -0600 |
> -----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.