tcg/optimize: Propagate sign info for bit counting

The results are generally 6 bit unsigned values, though
the count leading and trailing bits may produce any value
for a zero input.

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Luis Pires <luis.pires@eldorado.org.br>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

tcg/optimize.c

@@ -1229,7 +1229,7 @@ static bool fold_count_zeros(OptContext *ctx, TCGOp *op)
         g_assert_not_reached();
     }
     ctx->z_mask = arg_info(op->args[2])->z_mask | z_mask;
-
+    ctx->s_mask = smask_from_zmask(ctx->z_mask);
     return false;
 }
 
@@ -1249,6 +1249,7 @@ static bool fold_ctpop(OptContext *ctx, TCGOp *op)
     default:
         g_assert_not_reached();
     }
+    ctx->s_mask = smask_from_zmask(ctx->z_mask);
     return false;
 }