The grand cpu_switch register reshuffle!
In particular, use r8 to hold the old process, and r7 for medium-term scratch, saving r0-r3 for things we don't need saved over function calls. This gets rid of five register-to-register MOVs.
This commit is contained in:
bjh21
parent
e2a4ec505f
commit
7dd8880e90
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@ -1,4 +1,4 @@
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/* $NetBSD: cpuswitch.S,v 1.26 2002/10/18 21:32:57 bjh21 Exp $ */
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/* $NetBSD: cpuswitch.S,v 1.27 2002/10/18 23:06:33 bjh21 Exp $ */
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/*
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* Copyright (c) 1994-1998 Mark Brinicombe.
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@ -172,12 +172,13 @@ ASENTRY_NP(idle)
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ENTRY(cpu_switch)
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/*
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* Local register usage. Some of these registers are out of date.
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* r1 = oldproc
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* r0-r2 = scratch
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* r3 = whichqs
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* r4 = queue
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* r5 = &qs[queue]
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* r6 = newproc
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* r7 = scratch
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* r7 = &whichqs, new first proc in q, old pcb, new pcb
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* r8 = oldproc
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*/
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mov ip, sp
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stmfd sp!, {r4-r10, fp, ip, lr, pc}
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@ -188,15 +189,12 @@ ENTRY(cpu_switch)
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* a valid process (curproc = 0). Zero the current PCB pointer
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* while we're at it.
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*/
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ldr r7, .Lcurproc
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ldr r6, .Lcurpcb
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ldr r1, .Lcurproc
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ldr r2, .Lcurpcb
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mov r0, #0x00000000
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ldr r1, [r7] /* r1 = curproc */
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str r0, [r7] /* curproc = NULL */
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str r0, [r6] /* curpcb = NULL */
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/* stash the old proc while we call functions */
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mov r5, r1
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ldr r8, [r1] /* r8 = curproc */
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str r0, [r1] /* curproc = NULL */
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str r0, [r2] /* curpcb = NULL */
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#if defined(MULTIPROCESSOR) || defined(LOCKDEBUG)
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/* release the sched_lock before handling interrupts */
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@ -223,8 +221,8 @@ ENTRY(cpu_switch)
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ldr r7, .Lwhichqs
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/* rem: r5 = old proc */
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/* rem: r7 = &whichqs */
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/* rem: r8 = old proc */
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.Lswitch_search:
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IRQdisable
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@ -239,10 +237,7 @@ ENTRY(cpu_switch)
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teq r3, #0x00000000
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beq _ASM_LABEL(idle)
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/* put old proc back in r1 */
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mov r1, r5
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/* rem: r1 = old proc */
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/* rem: r8 = old proc */
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/* rem: r3 = whichqs */
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/* rem: interrupts are disabled */
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@ -270,9 +265,9 @@ ENTRY(cpu_switch)
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ldrb r4, [ r5, r4, lsr #26 ]
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/* rem: r0 = bit mask of chosen queue (1 << r4) */
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/* rem: r1 = old proc */
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/* rem: r3 = whichqs */
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/* rem: r4 = queue number */
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/* rem: r8 = old proc */
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/* rem: interrupts are disabled */
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/* Get the address of the queue (&qs[queue]) */
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@ -289,6 +284,8 @@ ENTRY(cpu_switch)
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ldr r7, [r6, #(P_FORW)]
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str r7, [r5, #(P_FORW)]
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/* rem: r7 = new queue head */
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/*
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* Test to see if the queue is now empty. If the head of the queue
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* points to the queue itself then there are no more processes in
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@ -299,8 +296,6 @@ ENTRY(cpu_switch)
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teq r5, r7
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biceq r3, r3, r0
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/* rem: r0 = bit mask of chosen queue (1 << r4) - NOT NEEDED AN MORE */
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/* Fix the back pointer for the process now at the head of the queue. */
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ldr r0, [r6, #(P_BACK)]
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str r0, [r7, #(P_BACK)]
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@ -309,16 +304,16 @@ ENTRY(cpu_switch)
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ldr r7, .Lwhichqs
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str r3, [r7]
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/* rem: r1 = old proc */
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/* rem: r8 = old proc */
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/* rem: r3 = whichqs - NOT NEEDED ANY MORE */
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/* rem: r4 = queue number - NOT NEEDED ANY MORE */
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/* rem: r6 = new process */
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/* rem: interrupts are disabled */
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/* Clear the want_resched flag */
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ldr r7, .Lwant_resched
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ldr r1, .Lwant_resched
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mov r0, #0x00000000
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str r0, [r7]
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str r0, [r1]
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/*
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* Clear the back pointer of the process we have removed from
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@ -330,9 +325,7 @@ ENTRY(cpu_switch)
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/*
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* unlock the sched_lock, but leave interrupts off, for now.
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*/
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mov r7, r1
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bl _C_LABEL(sched_unlock_idle)
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mov r1, r7
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#endif
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#ifdef MULTIPROCESSOR
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@ -359,7 +352,7 @@ ENTRY(cpu_switch)
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/* At this point we can allow IRQ's again. */
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IRQenable
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/* rem: r1 = old proc */
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/* rem: r8 = old proc */
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/* rem: r6 = new process */
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/* rem: interrupts are enabled */
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@ -367,36 +360,35 @@ ENTRY(cpu_switch)
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* If the new process is the same as the process that called
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* cpu_switch() then we do not need to save and restore any
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* contexts. This means we can make a quick exit.
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* The test is simple if curproc on entry (now in r1) is the
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* The test is simple if curproc on entry (now in r8) is the
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* same as the proc removed from the queue we can jump to the exit.
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*/
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teq r1, r6
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teq r8, r6
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beq .Lswitch_return
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/* Remember the old process in r0 */
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mov r0, r1
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/*
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* If the curproc on entry to cpu_switch was zero then the
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* process that called it was exiting. This means that we do
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* not need to save the current context. Instead we can jump
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* straight to restoring the context for the new process.
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*/
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teq r0, #0x00000000
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teq r8, #0x00000000
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beq .Lswitch_exited
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/* rem: r0 = old proc */
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/* rem: r8 = old proc */
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/* rem: r6 = new process */
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/* rem: interrupts are enabled */
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/* Stage two : Save old context */
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/* Get the user structure for the old process. */
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ldr r1, [r0, #(P_ADDR)]
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ldr r7, [r8, #(P_ADDR)]
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/* Save the remaining registers in the old process's pcb */
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add r7, r1, #(PCB_R11)
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stmia r7, {r11-r13}
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add r0, r7, #(PCB_R11)
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stmia r0, {r11-r13}
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/* rem: r7 = old pcb */
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/*
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* This can be optimised... We know we want to go from SVC32
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@ -407,23 +399,23 @@ ENTRY(cpu_switch)
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orr r2, r2, #(PSR_UND32_MODE | I32_bit)
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msr cpsr_c, r2
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str sp, [r1, #(PCB_UND_SP)]
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str sp, [r7, #(PCB_UND_SP)]
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msr cpsr_c, r3 /* Restore the old mode */
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/* rem: r0 = old proc */
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/* rem: r1 = old pcb */
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/* rem: r6 = new process */
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/* rem: r7 = old pcb */
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/* rem: r8 = old proc */
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/* rem: interrupts are enabled */
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/* What else needs to be saved Only FPA stuff when that is supported */
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/* r1 now free! */
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/* r7 now free! */
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/* Third phase : restore saved context */
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/* rem: r0 = old proc */
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/* rem: r6 = new process */
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/* rem: r8 = old proc */
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/* rem: interrupts are enabled */
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/*
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@ -452,10 +444,10 @@ ENTRY(cpu_switch)
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str r2, [r3]
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/* Get the user structure for the new process in r1 */
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ldr r1, [r6, #(P_ADDR)]
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ldr r7, [r6, #(P_ADDR)]
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/* Get the pagedir physical address for the process. */
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ldr r0, [r1, #(PCB_PAGEDIR)]
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ldr r0, [r7, #(PCB_PAGEDIR)]
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/* Switch the memory to the new process */
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ldr r3, .Lcpufuncs
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@ -471,15 +463,13 @@ ENTRY(cpu_switch)
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orr r2, r2, #(PSR_UND32_MODE)
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msr cpsr_c, r2
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ldr sp, [r1, #(PCB_UND_SP)]
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ldr sp, [r7, #(PCB_UND_SP)]
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msr cpsr_c, r3 /* Restore the old mode */
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/* Restore the saved registers from the PCB */
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add r7, r1, #PCB_R11
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ldmia r7, {r11-r13}
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mov r7, r1 /* preserve PCB pointer */
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add r0, r7, #PCB_R11
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ldmia r0, {r11-r13}
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#ifdef ARMFPE
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add r0, r1, #(USER_SIZE) & 0x00ff
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@ -610,7 +600,7 @@ ENTRY(switch_exit)
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str r0, [r1]
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ldr r7, .Lwhichqs /* r7 = &whichqs */
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mov r5, #0x00000000 /* r5 = old proc = NULL */
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mov r8, #0x00000000 /* r8 = old proc = NULL */
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b .Lswitch_search
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/* LINTSTUB: Func: void savectx(struct pcb *pcb) */
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