[PATCH v4 22/23] powerpc/syscall: Optimise checks in beginning of system_call_exception()

[Christophe Leroy]

Combine all tests of regs->msr into a single logical one.

Before the patch:

   0:   81 6a 00 84     lwz     r11,132(r10)
   4:   90 6a 00 88     stw     r3,136(r10)
   8:   69 60 00 02     xori    r0,r11,2
   c:   54 00 ff fe     rlwinm  r0,r0,31,31,31
  10:   0f 00 00 00     twnei   r0,0
  14:   69 63 40 00     xori    r3,r11,16384
  18:   54 63 97 fe     rlwinm  r3,r3,18,31,31
  1c:   0f 03 00 00     twnei   r3,0
  20:   69 6b 80 00     xori    r11,r11,32768
  24:   55 6b 8f fe     rlwinm  r11,r11,17,31,31
  28:   0f 0b 00 00     twnei   r11,0

After the patch:

   0:   81 6a 00 84     lwz     r11,132(r10)
   4:   90 6a 00 88     stw     r3,136(r10)
   8:   7d 6b 58 f8     not     r11,r11
   c:   71 6b c0 02     andi.   r11,r11,49154
  10:   0f 0b 00 00     twnei   r11,0

6 cycles less on powerpc 8xx (328 => 322 cycles).

Signed-off-by: Christophe Leroy <christophe.le...@csgroup.eu>
---
 arch/powerpc/kernel/syscall.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/kernel/syscall.c b/arch/powerpc/kernel/syscall.c
index a40775daa88b..47ae55f94d1c 100644
--- a/arch/powerpc/kernel/syscall.c
+++ b/arch/powerpc/kernel/syscall.c
@@ -28,6 +28,7 @@ notrace long system_call_exception(long r3, long r4, long r5,
                                   unsigned long r0, struct pt_regs *regs)
 {
        syscall_fn f;
+       unsigned long expected_msr;
 
        regs->orig_gpr3 = r3;
 
@@ -39,10 +40,13 @@ notrace long system_call_exception(long r3, long r4, long 
r5,
 
        trace_hardirqs_off(); /* finish reconciling */
 
+       expected_msr = MSR_PR;
        if (!IS_ENABLED(CONFIG_BOOKE) && !IS_ENABLED(CONFIG_40x))
-               BUG_ON(!(regs->msr & MSR_RI));
-       BUG_ON(!(regs->msr & MSR_PR));
-       BUG_ON(arch_irq_disabled_regs(regs));
+               expected_msr |= MSR_RI;
+       if (IS_ENABLED(CONFIG_PPC32))
+               expected_msr |= MSR_EE;
+       BUG_ON((regs->msr & expected_msr) ^ expected_msr);
+       BUG_ON(IS_ENABLED(CONFIG_PPC64) && arch_irq_disabled_regs(regs));
 
 #ifdef CONFIG_PPC_PKEY
        if (mmu_has_feature(MMU_FTR_PKEY)) {
-- 
2.25.0