This adds emulations for the popcntb, popcntw, and popcntd instructions.
Tested for correctness against the popcnt{b,w,d} instructions on ppc64le.

Signed-off-by: Matt Brown <redacted>
---
v2:
        - fixed opcodes
        - fixed typecasting
        - fixed bitshifting error for both 32 and 64bit arch
---
 arch/powerpc/lib/sstep.c | 43 ++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 42 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/lib/sstep.c b/arch/powerpc/lib/sstep.c
index 87d277f..e6a16a3 100644
--- a/arch/powerpc/lib/sstep.c
+++ b/arch/powerpc/lib/sstep.c

@@ -612,6 +612,35 @@ static nokprobe_inline void do_cmpb(struct pt_regs *regs, unsigned long v1,
        regs->gpr[rd] = out_val;
 }

+/*
+ * The size parameter is used to adjust the equivalent popcnt instruction.
+ * popcntb = 8, popcntw = 32, popcntd = 64
+ */
+static nokprobe_inline void do_popcnt(struct pt_regs *regs, unsigned long v1,
+                               int size, int ra)
+{
+       unsigned long long high, low, mask;
+       unsigned int n;
+       int i, j;
+
+       high = 0;
+       low = 0;
+
+       for (i = 0; i < (64 / size); i++) {
+               n = 0;
+               for (j = 0; j < size; j++) {
+                       mask = 1UL << (j + (i * size));
+                       if (v1 & mask)
+                               n++;
+               }
+               if ((i * size) < 32)
+                       low |= n << (i * size);
+               else
+                       high |= n << ((i * size) - 32);
+       }
+       regs->gpr[ra] = (high << 32) | low;
+}