Fix legalize-br-table test case for basic blocks. (#990)

cranelift/filetests/filetests/isa/x86/legalize-br-table-bb.clif

@@ -0,0 +1,31 @@
+test compile
+target x86_64
+feature "basic-blocks"
+; regex: V=v\d+
+; regex: EBB=ebb\d+
+
+function u0:0(i64) system_v {
+    ss0 = explicit_slot 1
+    jt0 = jump_table [ebb1]
+
+ebb0(v0: i64):
+    v1 = stack_addr.i64 ss0
+    v2 = load.i8 v1
+    br_table v2, ebb2, jt0
+; check:     $(oob=$V) = ifcmp_imm $(idx=$V), 1
+; ebb2 is replaced by ebb1 by fold_redundant_jump
+; nextln:    brif uge $oob, ebb1
+; nextln:    fallthrough $(inb=$EBB)
+; check:   $inb:
+; nextln:    $(final_idx=$V) = uextend.i64 $idx
+; nextln:    $(base=$V) = jump_table_base.i64 jt0
+; nextln:    $(rel_addr=$V) = jump_table_entry $final_idx, $base, 4, jt0
+; nextln:    $(addr=$V) = iadd $base, $rel_addr
+; nextln:    indirect_jump_table_br $addr, jt0
+
+ebb2:
+    jump ebb1
+
+ebb1:
+    return
+}

cranelift/filetests/filetests/isa/x86/legalize-br-table.clif

@@ -1,5 +1,4 @@
 test compile
-
 target x86_64
 feature !"basic-blocks"
 ; regex: V=v\d+