powerpc/perf: Use stack siar instead of mfspr

Minor optimization in the 'perf_instruction_pointer' function code by
making use of stack siar instead of mfspr.

Fixes: 75382aa72f06 ("powerpc/perf: Move code to select SIAR or pt_regs into perf_read_regs")
Signed-off-by: Kajol Jain <kjain@linux.ibm.com>
Tested-by: Nageswara R Sastry <rnsastry@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210818171556.36912-1-kjain@linux.ibm.com

diff --git a/arch/powerpc/perf/core-book3s.c b/arch/powerpc/perf/core-book3s.c
index 91203ed..3a782a3 100644 (file)
--- a/arch/powerpc/perf/core-book3s.c
+++ b/arch/powerpc/perf/core-book3s.c
@@ -2269,7 +2269,7 @@ unsigned long perf_instruction_pointer(struct pt_regs *regs)
                else
                        return regs->nip;
        } else if (use_siar && siar_valid(regs))
-               return mfspr(SPRN_SIAR) + perf_ip_adjust(regs);
+               return siar + perf_ip_adjust(regs);
        else if (use_siar)
                return 0;               // no valid instruction pointer
        else