README
No OneTemporary
Actions

Size

1 KB

Subscribers

None

README
View Options

	This directory contains mpn functions for various HP PA-RISC chips. Code
	that runs faster on the PA7100 and later implementations, is in the pa7100
	directory.

	RELEVANT OPTIMIZATION ISSUES

	Load and Store timing

	On the PA7000 no memory instructions can issue the two cycles after a store.
	For the PA7100, this is reduced to one cycle.

	The PA7100 has a lookup-free cache, so it helps to schedule loads and the
	dependent instruction really far from each other.

	STATUS

	1. mpn_mul_1 could be improved to 6.5 cycles/limb on the PA7100, using the
	instructions bwlow (but some sw pipelining is needed to avoid the
	xmpyu-fstds delay):

	fldds s1_ptr

	xmpyu
	fstds N(%r30)
	xmpyu
	fstds N(%r30)

	ldws N(%r30)
	ldws N(%r30)
	ldws N(%r30)
	ldws N(%r30)

	addc
	stws res_ptr
	addc
	stws res_ptr

	addib Loop

	2. mpn_addmul_1 could be improved from the current 10 to 7.5 cycles/limb
	(asymptotically) on the PA7100, using the instructions below. With proper
	sw pipelining and the unrolling level below, the speed becomes 8
	cycles/limb.

	fldds s1_ptr
	fldds s1_ptr

	xmpyu
	fstds N(%r30)
	xmpyu
	fstds N(%r30)
	xmpyu
	fstds N(%r30)
	xmpyu
	fstds N(%r30)

	ldws N(%r30)
	ldws N(%r30)
	ldws N(%r30)
	ldws N(%r30)
	ldws N(%r30)
	ldws N(%r30)
	ldws N(%r30)
	ldws N(%r30)
	addc
	addc
	addc
	addc
	addc %r0,%r0,cy-limb

	ldws res_ptr
	ldws res_ptr
	ldws res_ptr
	ldws res_ptr
	add
	stws res_ptr
	addc
	stws res_ptr
	addc
	stws res_ptr
	addc
	stws res_ptr

	addib