powerpc sstep: Add support for cnttzw, cnttzd instructions

This adds emulation support for the following integer instructions:
  * Count Trailing Zeros Word (cnttzw[.])
  * Count Trailing Zeros Doubleword (cnttzd[.])
Signed-off-by: Sandipan Das <sandipan@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/lib/sstep.c

@@ -1819,6 +1819,20 @@ int analyse_instr(struct instruction_op *op, const struct pt_regs *regs,
 		case 506:	/* popcntd */
 			do_popcnt(regs, op, regs->gpr[rd], 64);
 			goto logical_done_nocc;
+#endif
+		case 538:	/* cnttzw */
+			if (!cpu_has_feature(CPU_FTR_ARCH_300))
+				return -1;
+			val = (unsigned int) regs->gpr[rd];
+			op->val = (val ? __builtin_ctz(val) : 32);
+			goto logical_done;
+#ifdef __powerpc64__
+		case 570:	/* cnttzd */
+			if (!cpu_has_feature(CPU_FTR_ARCH_300))
+				return -1;
+			val = regs->gpr[rd];
+			op->val = (val ? __builtin_ctzl(val) : 64);
+			goto logical_done;
 #endif
 		case 922:	/* extsh */
 			op->val = (signed short) regs->gpr[rd];