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authorDavid Mosberger-Tang <davidm@hpl.hp.com>2005-04-28 00:16:07 -0400
committerTony Luck <tony.luck@intel.com>2005-04-28 00:16:07 -0400
commit96e017495e6833adcbad84783e3c5eb685836bbf (patch)
tree41504d1ba4f94282d109224936ae6829109c3e6d
parent3c79c8b1d92a9ae3edf3cbcd2c43c553ee0f1d83 (diff)
[IA64] On return from syscall, hint b7 with __kernel_syscall_via_epc().
Why is this a good idea? Clearing b7 to 0 is guaranteed to do us no good and writing it with __kernel_syscall_via_epc() yields a 6 cycle improvement _if_ the application performs another EPC-based system- call without overwriting b7, which is not all that uncommon. Well worth the minimal cost of 1 bundle of code. Signed-off-by: David Mosberger-Tang <davidm@hpl.hp.com> Signed-off-by: Tony Luck <tony.luck@intel.com>
-rw-r--r--arch/ia64/kernel/entry.S9
1 files changed, 8 insertions, 1 deletions
diff --git a/arch/ia64/kernel/entry.S b/arch/ia64/kernel/entry.S
index 0c84bed1bda9..6359d7ffbb7c 100644
--- a/arch/ia64/kernel/entry.S
+++ b/arch/ia64/kernel/entry.S
@@ -692,7 +692,7 @@ ENTRY(ia64_leave_syscall)
692 ;; 692 ;;
693(p6) ld4 r31=[r18] // load current_thread_info()->flags 693(p6) ld4 r31=[r18] // load current_thread_info()->flags
694 ld8 r19=[r2],PT(B6)-PT(LOADRS) // load ar.rsc value for "loadrs" 694 ld8 r19=[r2],PT(B6)-PT(LOADRS) // load ar.rsc value for "loadrs"
695 mov b7=r0 // clear b7 695 nop.i 0
696 ;; 696 ;;
697 ld8 r23=[r3],PT(R11)-PT(AR_BSPSTORE) // load ar.bspstore (may be garbage) 697 ld8 r23=[r3],PT(R11)-PT(AR_BSPSTORE) // load ar.bspstore (may be garbage)
698 ld8 r18=[r2],PT(R9)-PT(B6) // load b6 698 ld8 r18=[r2],PT(R9)-PT(B6) // load b6
@@ -754,7 +754,14 @@ ENTRY(ia64_leave_syscall)
754(pUStk) ld4 r17=[r3] // r17 = cpu_data->phys_stacked_size_p8 754(pUStk) ld4 r17=[r3] // r17 = cpu_data->phys_stacked_size_p8
755 mov.m ar.csd=r0 // M2 clear ar.csd 755 mov.m ar.csd=r0 // M2 clear ar.csd
756 mov f10=f0 // clear f10 756 mov f10=f0 // clear f10
757
758 nop.m 0
759 movl r14=__kernel_syscall_via_epc // X
757 ;; 760 ;;
761 nop.m 0
762 nop.m 0
763 mov b7=r14 // I0 clear b7 (hint with __kernel_syscall_via_epc)
764
758 mov r14=r0 // clear r14 765 mov r14=r0 // clear r14
759 mov f11=f0 // clear f11 766 mov f11=f0 // clear f11
760(pKStk) br.cond.dpnt.many skip_rbs_switch 767(pKStk) br.cond.dpnt.many skip_rbs_switch