Commit 458f9355 authored by David Mosberger-Tang's avatar David Mosberger-Tang Committed by Tony Luck

[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: default avatarDavid Mosberger-Tang <davidm@hpl.hp.com>
Signed-off-by: default avatarTony Luck <tony.luck@intel.com>
parent e15da401
......@@ -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)
......
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