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[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>
This commit is contained in:
David Mosberger-Tang 2005-05-04 13:25:00 -07:00 committed by Tony Luck
parent e15da40176
commit 458f935527
1 changed files with 19 additions and 0 deletions
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19
arch/ia64/kernel/ivt.S
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@ -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)