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powerpc: micro-optimize cpu_switch()

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Since the non-volatile registers are restored at the end of cpu_switchin (of
the new thread) they're free for us to use for our own purposes.  Load the
PCB_FLAGS into a non-volatile register so it's preserved across the C
function calls that manage FPU and altivec state.  This removes 4 loads from
each file.  Might be a trivial performance improvement (~12 clock cycles per
context switch).

MFC after:	3 weeks
This commit is contained in:
jhibbits 2019-04-27 00:53:41 +00:00
parent 1078dacf93
commit 2acb78e3a0
2 changed files with 18 additions and 24 deletions
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14
sys/powerpc/powerpc/swtch32.S
View File

@ -98,17 +98,16 @@ ENTRY(cpu_switch)
mr %r16,%r5 /* and the new lock */
mr %r17,%r6 /* and the PCB */
lwz %r7,PCB_FLAGS(%r17)
lwz %r18,PCB_FLAGS(%r17)
/* Save FPU context if needed */
andi. %r7, %r7, PCB_FPU
andi. %r7, %r18, PCB_FPU
beq .L1
bl save_fpu
.L1:
mr %r3,%r14 /* restore old thread ptr */
lwz %r7,PCB_FLAGS(%r17)
/* Save Altivec context if needed */
andi. %r7, %r7, PCB_VEC
andi. %r7, %r18, PCB_VEC
beq .L2
bl save_vec
@ -151,17 +150,16 @@ blocked_loop:
mr %r3,%r2 /* Get new thread ptr */
bl pmap_activate /* Activate the new address space */
lwz %r6, PCB_FLAGS(%r17)
lwz %r19, PCB_FLAGS(%r17)
/* Restore FPU context if needed */
andi. %r6, %r6, PCB_FPU
andi. %r6, %r19, PCB_FPU
beq .L3
mr %r3,%r2 /* Pass curthread to enable_fpu */
bl enable_fpu
.L3:
lwz %r6, PCB_FLAGS(%r17)
/* Restore Altivec context if needed */
andi. %r6, %r6, PCB_VEC
andi. %r6, %r19, PCB_VEC
beq .L4
mr %r3,%r2 /* Pass curthread to enable_vec */
bl enable_vec

28
sys/powerpc/powerpc/swtch64.S
View File

@ -125,26 +125,24 @@ ENTRY(cpu_switch)
stdu %r1,-48(%r1)
lwz %r7, PCB_FLAGS(%r17)
andi. %r7, %r7, PCB_CDSCR
lwz %r18, PCB_FLAGS(%r17)
andi. %r7, %r18, PCB_CDSCR
beq .L0
/* Custom DSCR was set. Reseting it to enter kernel */
li %r7, 0x0
mtspr SPR_DSCR, %r7
li %r6, 0x0
mtspr SPR_DSCR, %r6
.L0:
lwz %r7,PCB_FLAGS(%r17)
/* Save FPU context if needed */
andi. %r7, %r7, PCB_FPU
andi. %r7, %r18, PCB_FPU
beq .L1
bl save_fpu
nop
.L1:
mr %r3,%r14 /* restore old thread ptr */
lwz %r7,PCB_FLAGS(%r17)
/* Save Altivec context if needed */
andi. %r7, %r7, PCB_VEC
andi. %r7, %r18, PCB_VEC
beq .L2
bl save_vec
nop
@ -186,30 +184,28 @@ blocked_loop:
bl pmap_activate /* Activate the new address space */
nop
lwz %r6, PCB_FLAGS(%r17)
lwz %r19, PCB_FLAGS(%r17)
/* Restore FPU context if needed */
andi. %r6, %r6, PCB_FPU
andi. %r6, %r19, PCB_FPU
beq .L3
mr %r3,%r13 /* Pass curthread to enable_fpu */
bl enable_fpu
nop
.L3:
lwz %r6, PCB_FLAGS(%r17)
/* Restore Altivec context if needed */
andi. %r6, %r6, PCB_VEC
andi. %r6, %r19, PCB_VEC
beq .L31
mr %r3,%r13 /* Pass curthread to enable_vec */
bl enable_vec
nop
.L31:
lwz %r6, PCB_FLAGS(%r17)
/* Restore Custom DSCR if needed */
andi. %r6, %r6, PCB_CDSCR
andi. %r6, %r19, PCB_CDSCR
beq .L4
ld %r6, PCB_DSCR(%r17) /* Load the DSCR register*/
mtspr SPR_DSCR, %r6
ld %r7, PCB_DSCR(%r17) /* Load the DSCR register*/
mtspr SPR_DSCR, %r7
/* thread to restore is in r3 */
.L4: