erts: Stop supporting non-literal empty tuples

Since R12B, empty tuples are literals. Thus the compiler will no
longer generate the instruction:

  put_tuple 0 Destination

for creating an empty tuple. It is now time to stop supporting
that instruction in the run-time system.

While we are at it, correct a typo.

2 files changed, 7 insertions, 10 deletions

diff --git a/erts/emulator/beam/beam_emu.c b/erts/emulator/beam/beam_emu.c
index f0b04535dd..eb95999e55 100644
--- a/erts/emulator/beam/beam_emu.c
+++ b/erts/emulator/beam/beam_emu.c
@@ -3217,12 +3217,6 @@ apply_bif_or_nif_epilogue:
 	StoreBifResult(1, result);
     }
 
- OpCase(i_put_tuple_only_Ad): {
-     tmp_arg1 = make_tuple(HTOP);
-     *HTOP++ = Arg(0);
-     StoreBifResult(1, tmp_arg1);
- }
-
  OpCase(case_end_s):
     GetArg1(0, tmp_arg1);
     c_p->fvalue = tmp_arg1;
diff --git a/erts/emulator/beam/ops.tab b/erts/emulator/beam/ops.tab
index d6feef3fb9..802c6fd1eb 100644
--- a/erts/emulator/beam/ops.tab
+++ b/erts/emulator/beam/ops.tab
@@ -60,12 +60,18 @@ func_info M=a a==am_module_info A=u==0 | label L | move n r => too_old_compiler
 func_info M=a a==am_module_info A=u==1 | label L | move n r => too_old_compiler
 
 # The undocumented and unsupported guard BIF is_constant/1 was removed
-# in R13. The is_constant/2 operation is marked as obosolete in genop.tab,
+# in R13. The is_constant/2 operation is marked as obsolete in genop.tab,
 # so the loader will automatically generate a too_old_compiler message
 # it is used, but we need to handle the is_constant/1 BIF specially here.
 
 bif1 Fail u$func:erlang:is_constant/1 Src Dst => too_old_compiler
 
+# Since the constant pool was introduced in R12B, empty tuples ({})
+# are literals. Therefore we no longer need to allow put_tuple/2
+# with a tuple size of zero.
+
+put_tuple u==0 d => too_old_compiler
+
 #
 # All the other instructions.
 #
@@ -328,11 +334,8 @@ i_is_eq_immed f y c
 # Putting things.
 #
 
-put_tuple u==0 Dst => i_put_tuple_only u Dst
 put_tuple Arity Dst | put V => i_put_tuple Arity V Dst
 
-i_put_tuple_only A d
-
 %macro: i_put_tuple PutTuple -pack
 i_put_tuple A x x
 i_put_tuple A y x