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- Newsgroups: comp.dsp
- Path: sparky!uunet!telebit!phr
- From: phr@telebit.com (Paul Rubin)
- Subject: Re: compilers for DSP processors
- In-Reply-To: greg@gmp.lonestar.org's message of 22 Dec 92 14:58:02 GMT
- Message-ID: <PHR.92Dec22191419@napa.telebit.com>
- Sender: news@telebit.com
- Nntp-Posting-Host: napa.telebit.com
- Organization: Telebit Corporation; Sunnyvale, CA, USA
- References: <75774@apple.apple.COM> <FFV7VB1w164w@gmp.lonestar.org>
- Date: 22 Dec 92 19:14:19
- Lines: 24
-
- I did an application that decompressed G4 images and then scaled
- the images for a for a 300 page per minute printer . The C
- compiler was GNU and the risc was the Intel 80960CA. The code had
- beed optimized a lot in C and was still not fast enough.
-
- 300 pages per minute? 5 pages per second??? Yow!
-
- My usual experience with C compilers on DSP's that a 8 to 10 x
- increase in speed is possible in the c to asm port. After looking
- at the output of the GNU 80960 C compiler, I was impressed with
- the efficiency of the assembler output. I estimated that the
- increase in speed in the c to asm port would be a factor of 2 at
- best. I was able to attain a 3x speed increase on the G4
- decompression code and A 8X IMPROVEMENT on the scaling code.
-
- This speed increase was due to 1) using a machine instruction the
- complier was clueless about, and 2) an optimization of the scaling
- algorithmn that would have been not obvious at the compiler level.
-
- You should report the missing machine instruction to the maintainers
- of your compiler (I'm not sure which of the several available 960
- GCC ports you were using), or simply extend the compiler yourself
- to know about the extra instruction. Having the compiler sources
- is great.
-