Re: A bug in GCC 2.95.2 for SPARC

[James Cheng <James dot Cheng at eng dot sun dot com>]

David,

>    For performance reason. UltraSPARC is a 64-bit processor, where one
>    64-bit store (std) is faster than two 32-bit stores (st). We are
>    building a performance library for media applications.
> 
> Integer 'std' is deprecated in V9 and runs slower on UltraSparc than
> two 'st' stores.  Perhaps you really mean 'stx' integer stores, or
> 'stdf' double float stores?  The latter you can get with -mv8.

You are right that I was referring to 'stdf' which has a suggested asm
syntax of 'std freg, [address]'. The bug I encountered is that some gcc
generated 'stdf's are dealing with non-8-byte-aligned addresses, which
cause bus errors... Wait a minute. On page 222 of "The SPARC Architecture
Manual, Version 9", it reads:

	The store double floating-point instruction (STDF) copies
	a doubleword from a double floating-point register into a 
	word-aligned doubleword in memory.
	^^^^^^^^^^^^

But it seems to me that 'stdf' requires a doubleword-aligned address.
This might be the reason of this bug.

I am going to find the answer for this discrepancy.

Thanks,

-James