From: David Mosberger-Tang Date: Thu, 28 Apr 2005 04:16:07 +0000 (-0700) Subject: [IA64] On return from syscall, hint b7 with __kernel_syscall_via_epc(). X-Git-Tag: v2.6.13-rc2~59^2~14^2~13 X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=96e017495e6833adcbad84783e3c5eb685836bbf;p=linux-2.6 [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 Signed-off-by: Tony Luck --- diff --git a/arch/ia64/kernel/entry.S b/arch/ia64/kernel/entry.S index 0c84bed1bd..6359d7ffbb 100644 --- a/arch/ia64/kernel/entry.S +++ b/arch/ia64/kernel/entry.S @@ -692,7 +692,7 @@ ENTRY(ia64_leave_syscall) ;; (p6) ld4 r31=[r18] // load current_thread_info()->flags ld8 r19=[r2],PT(B6)-PT(LOADRS) // load ar.rsc value for "loadrs" - mov b7=r0 // clear b7 + nop.i 0 ;; ld8 r23=[r3],PT(R11)-PT(AR_BSPSTORE) // load ar.bspstore (may be garbage) ld8 r18=[r2],PT(R9)-PT(B6) // load b6 @@ -754,7 +754,14 @@ ENTRY(ia64_leave_syscall) (pUStk) ld4 r17=[r3] // r17 = cpu_data->phys_stacked_size_p8 mov.m ar.csd=r0 // M2 clear ar.csd mov f10=f0 // clear f10 + + nop.m 0 + movl r14=__kernel_syscall_via_epc // X ;; + nop.m 0 + nop.m 0 + mov b7=r14 // I0 clear b7 (hint with __kernel_syscall_via_epc) + mov r14=r0 // clear r14 mov f11=f0 // clear f11 (pKStk) br.cond.dpnt.many skip_rbs_switch