Commit 458f9355 authored May 04, 2005 by David Mosberger-Tang Committed by Tony Luck Jun 28, 2005

[IA64] Speed up lfetch.fault [NULL]

This patch greatly speeds up the handling of lfetch.fault instructions
which result in NaT consumption. Due to the NaT-page mapped at address
0, this is guaranteed to happen when lfetch.fault'ing a NULL pointer.
With this patch in place, we can even define prefetch()/prefetchw() as
lfetch.fault without significant performance degradation. More
importantly, it allows compilers to be more aggressive with using
lfetch.fault on pointers that might be NULL.

Signed-off-by: David Mosberger-Tang <davidm@hpl.hp.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>

parent e15da401

arch/ia64/kernel/ivt.S

+19 −0

Original line number	Diff line number	Diff line
		@@ -1243,6 +1243,25 @@ END(disabled_fp_reg)
		// 0x5600 Entry 26 (size 16 bundles) Nat Consumption (11,23,37,50)
		ENTRY(nat_consumption)
		DBG_FAULT(26)

		mov r16=cr.ipsr
		mov r17=cr.isr
		mov r31=pr // save PR
		;;
		and r18=0xf,r17 // r18 = cr.ipsr.code{3:0}
		tbit.z p6,p0=r17,IA64_ISR_NA_BIT
		;;
		cmp.ne.or p6,p0=IA64_ISR_CODE_LFETCH,r18
		dep r16=-1,r16,IA64_PSR_ED_BIT,1
		(p6) br.cond.spnt 1f // branch if (cr.ispr.na == 0 \|\| cr.ipsr.code{3:0} != LFETCH)
		;;
		mov cr.ipsr=r16 // set cr.ipsr.na
		mov pr=r31,-1
		;;
		rfi

		1: mov pr=r31,-1
		;;
		FAULT(26)
		END(nat_consumption)