From 3c79c8b1d92a9ae3edf3cbcd2c43c553ee0f1d83 Mon Sep 17 00:00:00 2001
From: David Mosberger-Tang <davidm@hpl.hp.com>
Date: Wed, 27 Apr 2005 21:15:13 -0700
Subject: [PATCH] [IA64] Schedule fp-clearing insns at least 6 cycles after
 reading ar.bsp.

Decreases syscall overhead by approximately 6 cycles.

Signed-off-by: David Mosberger-Tang <davidm@hpl.hp.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
---
 arch/ia64/kernel/entry.S | 25 +++++++++++++++----------
 1 file changed, 15 insertions(+), 10 deletions(-)

diff --git a/arch/ia64/kernel/entry.S b/arch/ia64/kernel/entry.S
index c0f28339d58b..0c84bed1bda9 100644
--- a/arch/ia64/kernel/entry.S
+++ b/arch/ia64/kernel/entry.S
@@ -705,15 +705,15 @@ ENTRY(ia64_leave_syscall)
 	// start restoring the state saved on the kernel stack (struct pt_regs):
 	ld8 r9=[r2],PT(CR_IPSR)-PT(R9)
 	ld8 r11=[r3],PT(CR_IIP)-PT(R11)
-	mov f6=f0		// clear f6
+	nop.i 0
 	;;
 	invala			// M0|1 invalidate ALAT
 	rsm psr.i | psr.ic	// M2 initiate turning off of interrupt and interruption collection
-	mov f9=f0		// clear f9
+	nop.i 0
 
 	ld8 r29=[r2],16		// load cr.ipsr
 	ld8 r28=[r3],16			// load cr.iip
-	mov f8=f0		// clear f8
+	mov r22=r0		// clear r22
 	;;
 	ld8 r30=[r2],16		// M0|1 load cr.ifs
 	ld8 r25=[r3],16		// M0|1 load ar.unat
@@ -721,15 +721,15 @@ ENTRY(ia64_leave_syscall)
 	;;
 	ld8 r26=[r2],PT(B0)-PT(AR_PFS)	// M0|1 load ar.pfs
 (pKStk)	mov r22=psr		// M2 read PSR now that interrupts are disabled
-	mov f10=f0		// clear f10
+(pUStk) add r14=IA64_TASK_THREAD_ON_USTACK_OFFSET,r13
 	;;
 	ld8 r21=[r2],PT(AR_RNAT)-PT(B0) // load b0
 	ld8 r27=[r3],PT(PR)-PT(AR_RSC)	// load ar.rsc
-	mov f11=f0		// clear f11
+	mov f6=f0		// clear f6
 	;;
 	ld8 r24=[r2],PT(AR_FPSR)-PT(AR_RNAT)	// load ar.rnat (may be garbage)
 	ld8 r31=[r3],PT(R1)-PT(PR)		// load predicates
-(pUStk) add r14=IA64_TASK_THREAD_ON_USTACK_OFFSET,r13
+	mov f7=f0		// clear f7
 	;;
 	ld8 r20=[r2],PT(R12)-PT(AR_FPSR)	// load ar.fpsr
 	ld8.fill r1=[r3],16	// load r1
@@ -737,24 +737,29 @@ ENTRY(ia64_leave_syscall)
 	;;
 	srlz.d			// M0  ensure interruption collection is off
 	ld8.fill r13=[r3],16
-	mov f7=f0		// clear f7
+	mov f8=f0		// clear f8
 	;;
 	ld8.fill r12=[r2]	// restore r12 (sp)
 	mov.m ar.ssd=r0		// M2 clear ar.ssd
-	mov r22=r0		// clear r22
+	mov b6=r18		// I0  restore b6
 
+	nop.m 0
+	mov f9=f0		// clear f9
+	shr.u r18=r19,16	// I0|1 get byte size of existing "dirty" partition
+	;;
 	ld8.fill r15=[r3]	// restore r15
 (pUStk) st1 [r14]=r17
 	addl r3=THIS_CPU(ia64_phys_stacked_size_p8),r0
 	;;
 (pUStk)	ld4 r17=[r3]		// r17 = cpu_data->phys_stacked_size_p8
 	mov.m ar.csd=r0		// M2 clear ar.csd
-	mov b6=r18		// I0  restore b6
+	mov f10=f0		// clear f10
 	;;
 	mov r14=r0		// clear r14
-	shr.u r18=r19,16	// I0|1 get byte size of existing "dirty" partition
+	mov f11=f0		// clear f11
 (pKStk) br.cond.dpnt.many skip_rbs_switch
 
+
 	mov.m ar.ccv=r0		// clear ar.ccv
 (pNonSys) br.cond.dpnt.many dont_preserve_current_frame
 	br.cond.sptk.many rbs_switch
-- 
2.39.5