Copyright 2002, 2005 Free Software Foundation, Inc.

This file is part of the GNU MP Library.

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  * the GNU General Public License as published by the Free Software

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    later version.

or both in parallel, as here.

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or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

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                    POWERPC 32-BIT MPN SUBROUTINES

This directory contains mpn functions for various 32-bit PowerPC chips.

CODE ORGANIZATION

	directory	  used for

	================================================

	powerpc           generic, 604, 604e, 744x, 745x

	powerpc/750       740, 750, 7400, 7410

The top-level powerpc directory is currently mostly aimed at 604/604e but

should be reasonable on all powerpcs.

STATUS

The code is quite well optimized for the 604e, other chips have had less

attention.

Altivec SIMD available in 74xx might hold some promise, but unfortunately

GMP only guarantees 32-bit data alignment, so there's lots of fiddling

around with partial operations at the start and end of limb vectors.  A

128-bit limb would be a novel idea, but is unlikely to be practical, since

it would have to work with ordinary +, -, * etc in the C code.

Also, Altivec isn't very well suited for the GMP multiplication needs.

Using floating-point based multiplication has much better better performance

potential for all current powerpcs, both the ones with slow integer multiply

units (603, 740, 750, 7400, 7410) and those with fast (604, 604e, 744x,

745x).  This is because all powerpcs do some level of pipelining in the FPU:

603 and 750 can sustain one fmadd every 2nd cycle.

604 and 604e can sustain one fmadd per cycle.

7400 and 7410 can sustain 3 fmadd in 4 cycles.

744x and 745x can sustain 4 fmadd in 5 cycles.

REGISTER NAMES

The normal powerpc convention is to give registers as plain numbers, like

"mtctr 6", but on Apple MacOS X (powerpc*-*-rhapsody* and

powerpc*-*-darwin*) the assembler demands an "r" like "mtctr r6".  Note

however when register 0 in an instruction means a literal zero the "r" is

omitted, for instance "lwzx r6,0,r7".

The GMP code uses the "r" forms, powerpc-defs.m4 transforms them to plain

numbers according to what GMP_ASM_POWERPC_R_REGISTERS finds is needed.

(Note that this style isn't fully general, as the identifier r4 and the

register r4 will not be distinguishable on some systems.  However, this is

not a problem for the limited GMP assembly usage.)

GLOBAL REFERENCES

Linux non-PIC

	lis	9, __gmp_binvert_limb_table@ha

	rlwinm	11, 5, 31, 25, 31

	la	9, __gmp_binvert_limb_table@l(9)

	lbzx	11, 9, 11

Linux PIC (FIXME)

.LCL0:

	.long .LCTOC1-.LCF0

	bcl	20, 31, .LCF0

.LCF0:

	mflr	30

	lwz	7, .LCL0-.LCF0(30)

	add	30, 7, 30

	lwz	11, .LC0-.LCTOC1(30)

	rlwinm	3, 5, 31, 25, 31

	lbzx	7, 11, 3

AIX (always PIC)

LC..0:

	.tc __gmp_binvert_limb_table[TC],__gmp_binvert_limb_table[RW]

	lwz	9, LC..0(2)

	rlwinm	0, 5, 31, 25, 31

	lbzx	0, 9, 0

Darwin (non-PIC)

	lis	r2, ha16(___gmp_binvert_limb_table)

	rlwinm	r9, r5, 31, 25, 31

	la	r2, lo16(___gmp_binvert_limb_table)(r2)

	lbzx	r0, r2, r9

Darwin (PIC)

	mflr	r0

	bcl	20, 31, L0001$pb

L0001$pb:

	mflr	r7

	mtlr	r0

	addis	r2, r7, ha16(L___gmp_binvert_limb_table$non_lazy_ptr-L0001$pb)

	rlwinm	r9, r5, 31, 25, 31

	lwz	r2, lo16(L___gmp_binvert_limb_table$non_lazy_ptr-L0001$pb)(r2)

	lbzx	r0, r2, r9

------

	.non_lazy_symbol_pointer

L___gmp_binvert_limb_table$non_lazy_ptr:

	.indirect_symbol ___gmp_binvert_limb_table

	.long	0

	.subsections_via_symbols

For GNU/Linux and Darwin, we might want to duplicate __gmp_binvert_limb_table

into the text section in this file.  We should thus be able to reach it like

this:

	blr	L0

L0:	mflr	r2

	rlwinm	r9, r5, 31, 25, 31

	addi	r9, r9, lo16(local_binvert_table-L0)

	lbzx	r0, r2, r9

REFERENCES

PowerPC Microprocessor Family: The Programming Environments for 32-bit

Microprocessors, IBM document G522-0290-01, 2000.

PowerPC 604e RISC Microprocessor User's Manual with Supplement for PowerPC

604 Microprocessor, IBM document G552-0330-00, Freescale document

MPC604EUM/AD, 3/1998.

MPC7410/MPC7400 RISC Microprocessor User's Manual, Freescale document

MPC7400UM/D, rev 1, 11/2002.

MPC7450 RISC Microprocessor Family Reference Manual, Freescale document

MPC7450UM, rev 5, 1/2005.

The above are available online from

	http://www.ibm.com/chips/techlib/techlib.nsf/productfamilies/PowerPC

	http://www.freescale.com/PowerPC

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