|Re: Q: P6 branch prediction email@example.com.OZ.AU (1996-05-01)|
|Re: Q: P6 branch prediction firstname.lastname@example.org (1996-05-14)|
|Re: Using memory below the SP (Was: Q: P6 branch prediction) email@example.com (1996-05-18)|
|Re: Using memory below the SP (Was: Q: P6 branch prediction) firstname.lastname@example.org (Michael Meissner) (1996-05-24)|
|From:||Michael Meissner <email@example.com>|
|Date:||24 May 1996 15:34:40 -0400|
|References:||<3179B05D.firstname.lastname@example.org> <email@example.com.OZ.AU> 96-05-012 96-05-100 96-05-105|
firstname.lastname@example.org (Zalman Stern) writes:
| Using the IBM calling convention on PowerPC, the 64 bytes immediately
| below the stack pointer (that is just outside the stack region) are
| guaranteed to be useable by a fucntion. This gives a function access
| to a small amount of memory without the expense of buying a stack
| frame. So on that platform, this technique is undeniably safe.
Its actually 220 bytes according to the ABI (so that r31 - r13, and f31 - f14
can be stored before updating the stack pointer). This usage is in fact
blest by the ABI (page 3-26 of the June 30th PowerOpen ABI).
Note, for the System V.4 and EABI ABI's, there is no such guarantee of space
beyond the current stack pointer.
Michael Meissner, Cygnus Support (East Coast)
Suite 105, 48 Grove Street, Somerville, MA 02144, USA
email@example.com, 617-629-3016 (office), 617-629-3010 (fax)
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