Make the 'r' operand type optional

The 'r' type is now mandatory. That means in order to handle
both of the following instructions:

  move x(0) y(7)
  move x(1) y(7)

we would need to define two specific operations in ops.tab:

  move r y
  move x y

We want to make 'r' operands optional. That is, if we have
only this specific instruction:

  move x y

it will match both of the following instructions:

  move x(0) y(7)
  move x(1) y(7)

Make 'r' optional allows us to save code space when we don't
want to make handling of x(0) a special case, but we can still
use 'r' to optimize commonly used instructions.

1 files changed, 155 insertions, 301 deletions

diff --git a/erts/emulator/beam/ops.tab b/erts/emulator/beam/ops.tab
index 4fa6a087e2..335f8e2db5 100644
--- a/erts/emulator/beam/ops.tab
+++ b/erts/emulator/beam/ops.tab
@@ -39,8 +39,8 @@ too_old_compiler | never() =>
 # necessary.) Since the instructions don't work correctly in R12B, simply
 # refuse to load the module.
 
-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
+func_info M=a a==am_module_info A=u==0 | label L | move n x==0 => too_old_compiler
+func_info M=a a==am_module_info A=u==1 | label L | move n x==0 => too_old_compiler
 
 # The undocumented and unsupported guard BIF is_constant/1 was removed
 # in R13. The is_constant/2 operation is marked as obsolete in genop.tab,
@@ -77,14 +77,14 @@ return
 # there is no line/1 instruction between the move and the call.
 #
 
-move S r | line Loc | call_ext Ar Func => \
-     line Loc | move S r | call_ext Ar Func
-move S r | line Loc | call_ext_last Ar Func=u$is_bif D => \
-     line Loc | move S r | call_ext_last Ar Func D
-move S r | line Loc | call_ext_only Ar Func=u$is_bif => \
-     line Loc | move S r | call_ext_only Ar Func
-move S r | line Loc | call Ar Func => \
-     line Loc | move S r | call Ar Func
+move S X0=x==0 | line Loc | call_ext Ar Func => \
+     line Loc | move S X0 | call_ext Ar Func
+move S X0=x==0 | line Loc | call_ext_last Ar Func=u$is_bif D => \
+     line Loc | move S X0 | call_ext_last Ar Func D
+move S X0=x==0 | line Loc | call_ext_only Ar Func=u$is_bif => \
+     line Loc | move S X0 | call_ext_only Ar Func
+move S X0=x==0 | line Loc | call Ar Func => \
+     line Loc | move S X0 | call Ar Func
 
 #
 # A tail-recursive call to an external function (non-BIF) will
@@ -167,31 +167,24 @@ is_tuple Fail=f S | select_tuple_arity S=d Fail=f Size=u Rest=* => \
 select_tuple_arity S=d Fail=f Size=u Rest=* => \
   gen_select_tuple_arity(S, Fail, Size, Rest)
 
-i_select_val_bins r f I
 i_select_val_bins x f I
 i_select_val_bins y f I
 
-i_select_val_lins r f I
 i_select_val_lins x f I
 i_select_val_lins y f I
 
-i_select_val2 r f c c f f
 i_select_val2 x f c c f f
 i_select_val2 y f c c f f
 
-i_select_tuple_arity r f I
 i_select_tuple_arity x f I
 i_select_tuple_arity y f I
 
-i_select_tuple_arity2 r f A A f f
 i_select_tuple_arity2 x f A A f f
 i_select_tuple_arity2 y f A A f f
 
-i_jump_on_val_zero r f I
 i_jump_on_val_zero x f I
 i_jump_on_val_zero y f I
 
-i_jump_on_val r f I I
 i_jump_on_val x f I I
 i_jump_on_val y f I I
 
@@ -203,30 +196,13 @@ is_ne_exact L1 S1 S2 | jump Fail | label L2 | same_label(L1, L2) => \
 %macro: get_list GetList -pack
 get_list x x x
 get_list x x y
-get_list x x r
 get_list x y x
 get_list x y y
-get_list x y r
-get_list x r x
-get_list x r y
 
 get_list y x x
 get_list y x y
-get_list y x r
 get_list y y x
 get_list y y y
-get_list y y r
-get_list y r x
-get_list y r y
-
-get_list r x x
-get_list r x y
-get_list r x r
-get_list r y x
-get_list r y y
-get_list r y r
-get_list r r x
-get_list r r y
 
 # Old-style catch.
 catch y f
@@ -247,21 +223,15 @@ set_tuple_element s d P
 
 %macro: i_get_tuple_element GetTupleElement -pack
 i_get_tuple_element x P x
-i_get_tuple_element r P x
 i_get_tuple_element y P x
-i_get_tuple_element x P r
-i_get_tuple_element y P r
 
 %cold
-i_get_tuple_element r P r
 i_get_tuple_element x P y
-i_get_tuple_element r P y
 i_get_tuple_element y P y
 %hot
 
 %macro: is_number IsNumber -fail_action
 %cold
-is_number f r
 is_number f x
 is_number f y
 %hot
@@ -271,16 +241,12 @@ is_number Fail Literal=q => move Literal x | is_number Fail x
 
 jump f
 
-case_end Literal=c => move Literal x | case_end x
-badmatch Literal=c => move Literal x | badmatch x
+case_end NotInX=cy => move NotInX x | case_end x
+badmatch NotInX=cy => move NotInX x | badmatch x
 
-case_end r
 case_end x
-case_end y
 
-badmatch r
 badmatch x
-badmatch y
 
 if_end
 raise s s
@@ -289,7 +255,7 @@ raise s s
 badarg j
 system_limit j
 
-move C=cxy r | jump Lbl => move_jump Lbl C
+move C=cxy x==0 | jump Lbl => move_jump Lbl C
 
 %macro: move_jump MoveJump -nonext
 move_jump f n
@@ -307,8 +273,6 @@ move_window/6
 
 # x -> y
 
-move S1=r S2=y | move X1=x Y1=y => move2 S1 S2 X1 Y1
-
 move X1=x Y1=y | move X2=x Y2=y | move X3=x Y3=y | succ(Y1,Y2) | succ(Y2,Y3) => \
     move_window X1 X2 X3 Y1 Y3
 
@@ -329,12 +293,13 @@ move X1=x Y1=y | move X2=x Y2=y => move2 X1 Y1 X2 Y2
 move Y1=y X1=x | move Y2=y X2=x => move2 Y1 X1 Y2 X2
 move X1=x X2=x | move X3=x X4=x => move2 X1 X2 X3 X4
 
-move S1=x S2=r | move S3=x S4=x => move2 S1 S2 S3 S4
-move S1=x S2=r | move X1=x Y1=y => move2 S1 S2 X1 Y1
-move S1=y S2=r | move X1=x Y1=y => move2 S1 S2 X1 Y1
+move X1=x X2=x | move X3=x Y1=y => move2 X1 X2 X3 Y1
+
+move S1=x S2=x | move X1=x Y1=y => move2 S1 S2 X1 Y1
+move S1=y S2=x | move X1=x Y1=y => move2 S1 S2 X1 Y1
 
-move Y1=y X1=x | move S1=r D1=x => move2 Y1 X1 S1 D1
-move S1=r D1=x | move Y1=y X1=x => move2 S1 D1 Y1 X1
+move Y1=y X1=x | move S1=x D1=x => move2 Y1 X1 S1 D1
+move S1=x D1=x | move Y1=y X1=x => move2 S1 D1 Y1 X1
 
 move2 X1=x Y1=y X2=x Y2=y | move X3=x Y3=y => move3 X1 Y1 X2 Y2 X3 Y3
 move2 Y1=y X1=x Y2=y X2=x | move Y3=y X3=x => move3 Y1 X1 Y2 X2 Y3 X3
@@ -351,14 +316,13 @@ move2 x y x y
 move2 y x y x
 move2 x x x x
 
-move2 x r x x
+move2 x x x y
 
-move2 x r x y
-move2 r y x y
-move2 y r x y
+move2 x y x y
+move2 y x x y
 
-move2 r x y x
-move2 y x r x
+move2 x x y x
+move2 y x x x
 
 %macro: move3 Move3
 move3 x y x y x y
@@ -373,20 +337,14 @@ move S=c D=y => move S x | move x D
 %macro:move Move -pack -gen_dest
 move x x
 move x y
-move x r
 move y x
-move y r
-move r x
-move r y
-move c r
 move c x
 move n x
-move n r
 move y y
 
 # Receive operations.
 
-loop_rec Fail Src | smp_mark_target_label(Fail) => i_loop_rec Fail Src
+loop_rec Fail x==0 | smp_mark_target_label(Fail) => i_loop_rec Fail
 
 label L | wait_timeout Fail Src | smp_already_locked(L) => label L | i_wait_timeout_locked Fail Src
 wait_timeout Fail Src => i_wait_timeout Fail Src
@@ -401,7 +359,7 @@ label L | timeout | smp_already_locked(L) => label L | timeout_locked
 remove_message
 timeout
 timeout_locked
-i_loop_rec f r
+i_loop_rec f
 loop_rec_end f
 wait f
 wait_locked f
@@ -419,29 +377,25 @@ send
 # Optimized comparisons with one immediate/literal operand.
 #
 
-is_eq_exact Lbl R=rxy C=ian => i_is_eq_exact_immed Lbl R C
-is_eq_exact Lbl R=rxy C=q => i_is_eq_exact_literal R Lbl C
+is_eq_exact Lbl R=xy C=ian => i_is_eq_exact_immed Lbl R C
+is_eq_exact Lbl R=xy C=q => i_is_eq_exact_literal Lbl R C
 
-is_ne_exact Lbl R=rxy C=ian => i_is_ne_exact_immed Lbl R C
-is_ne_exact Lbl R=rxy C=q => i_is_ne_exact_literal R Lbl C
+is_ne_exact Lbl R=xy C=ian => i_is_ne_exact_immed Lbl R C
+is_ne_exact Lbl R=xy C=q => i_is_ne_exact_literal Lbl R C
 
 %macro: i_is_eq_exact_immed EqualImmed -fail_action
-i_is_eq_exact_immed f r c
 i_is_eq_exact_immed f x c
 i_is_eq_exact_immed f y c
 
-i_is_eq_exact_literal r f c
-i_is_eq_exact_literal x f c
-i_is_eq_exact_literal y f c
+i_is_eq_exact_literal f x c
+i_is_eq_exact_literal f y c
 
 %macro: i_is_ne_exact_immed NotEqualImmed -fail_action
-i_is_ne_exact_immed f r c
 i_is_ne_exact_immed f x c
 i_is_ne_exact_immed f y c
 
-i_is_ne_exact_literal r f c
-i_is_ne_exact_literal x f c
-i_is_ne_exact_literal y f c
+i_is_ne_exact_literal f x c
+i_is_ne_exact_literal f y c
 
 #
 # Common Compare Specializations
@@ -449,31 +403,21 @@ i_is_ne_exact_literal y f c
 # to keep the instruction set small-ish
 #
 
-is_eq_exact Lbl S1=xy S2=r => is_eq_exact Lbl S2 S1
-is_eq_exact Lbl S1=rx S2=xy => i_is_eq_exact_spec Lbl S1 S2
+is_eq_exact Lbl S1=y S2=x => is_eq_exact Lbl S2 S1
+is_eq_exact Lbl S1=x S2=xy => i_is_eq_exact_spec Lbl S1 S2
 %macro: i_is_eq_exact_spec EqualExact -fail_action
 
 i_is_eq_exact_spec f x x
 i_is_eq_exact_spec f x y
-i_is_eq_exact_spec f r x
-i_is_eq_exact_spec f r y
-%cold
-i_is_eq_exact_spec f r r
-%hot
 
-is_lt Lbl S1=rxc S2=rxc  => i_is_lt_spec Lbl S1 S2
+is_lt Lbl S1=xc S2=xc  => i_is_lt_spec Lbl S1 S2
 
 %macro: i_is_lt_spec IsLessThan -fail_action
 
 i_is_lt_spec f x x
-i_is_lt_spec f x r
 i_is_lt_spec f x c
-i_is_lt_spec f r x
-i_is_lt_spec f r c
 i_is_lt_spec f c x
-i_is_lt_spec f c r
 %cold
-i_is_lt_spec f r r
 i_is_lt_spec f c c
 %hot
 
@@ -523,7 +467,6 @@ i_put_tuple Dst Arity Puts=* | put S => \
 i_put_tuple/2
 
 %macro:i_put_tuple PutTuple -pack -goto:do_put_tuple
-i_put_tuple r I
 i_put_tuple x I
 i_put_tuple y I
 
@@ -540,48 +483,25 @@ put_list x n x
 put_list y n x
 put_list x x x
 put_list y x x
-put_list x x r
-put_list y r r
 
 put_list y y x
 put_list x y x
-put_list r x x
-put_list r y x
-put_list r x r
-put_list y y r
-put_list y r x
-put_list r n x
-
-put_list x r x
-put_list x y r
-put_list y x r
-put_list y x x
 
-put_list x r r
+put_list y x x
 
 # put_list SrcReg Constant Dst
-put_list r c r
-put_list r c x
-put_list r c y
 
-put_list x c r
 put_list x c x
 put_list x c y
 
-put_list y c r
 put_list y c x
 put_list y c y
 
 # put_list Constant SrcReg Dst
-put_list c r r
-put_list c r x
-put_list c r y
 
-put_list c x r
 put_list c x x
 put_list c x y
 
-put_list c y r
 put_list c y x
 put_list c y y
 
@@ -590,18 +510,12 @@ put_list s s d
 %hot
 
 %macro: i_fetch FetchArgs -pack
-i_fetch c r
 i_fetch c x
 i_fetch c y
-i_fetch r c
-i_fetch r x
-i_fetch r y
 i_fetch x c
-i_fetch x r
 i_fetch x x
 i_fetch x y
 i_fetch y c
-i_fetch y r
 i_fetch y x
 i_fetch y y
 
@@ -629,27 +543,27 @@ return_trace
 # Note: There is no 'move_return y r', since there never are any y registers
 # when we do move_return (if we have y registers, we must do move_deallocate_return).
 
-move S r | return => move_return S r
+move S x==0 | return => move_return S
 
 %macro: move_return MoveReturn -nonext
-move_return x r
-move_return c r
-move_return n r
+move_return x
+move_return c
+move_return n
 
-move S r | deallocate D | return => move_deallocate_return S r D
+move S x==0 | deallocate D | return => move_deallocate_return S D
 
 %macro: move_deallocate_return MoveDeallocateReturn -pack -nonext
-move_deallocate_return x r Q
-move_deallocate_return y r Q
-move_deallocate_return c r Q
-move_deallocate_return n r Q
+move_deallocate_return x Q
+move_deallocate_return y Q
+move_deallocate_return c Q
+move_deallocate_return n Q
 
 deallocate D | return => deallocate_return D
 
 %macro: deallocate_return DeallocateReturn -nonext
 deallocate_return Q
 
-test_heap Need u==1 | put_list Y=y r r => test_heap_1_put_list Need Y
+test_heap Need u==1 | put_list Y=y x==0 x==0 => test_heap_1_put_list Need Y
 
 %macro: test_heap_1_put_list TestHeapPutList -pack
 test_heap_1_put_list I y
@@ -658,18 +572,16 @@ test_heap_1_put_list I y
 
 is_tuple Fail Literal=q => move Literal x | is_tuple Fail x
 is_tuple Fail=f c => jump Fail
-is_tuple Fail=f S=rxy | test_arity Fail=f S=rxy Arity => is_tuple_of_arity Fail S Arity
+is_tuple Fail=f S=xy | test_arity Fail=f S=xy Arity => is_tuple_of_arity Fail S Arity
 
 %macro:is_tuple_of_arity IsTupleOfArity -fail_action
 
 is_tuple_of_arity f x A
 is_tuple_of_arity f y A
-is_tuple_of_arity f r A
 
 %macro: is_tuple IsTuple -fail_action
 is_tuple f x
 is_tuple f y
-is_tuple f r
 
 test_arity Fail Literal=q Arity => move Literal x | test_arity Fail x Arity
 test_arity Fail=f c Arity => jump Fail
@@ -677,7 +589,6 @@ test_arity Fail=f c Arity => jump Fail
 %macro: test_arity IsArity -fail_action
 test_arity f x A
 test_arity f y A
-test_arity f r A
 
 is_tuple_of_arity Fail=f Reg Arity | get_tuple_element Reg P=u==0 Dst=xy => \
   is_tuple_of_arity Fail Reg Arity | extract_next_element Dst | original_reg Reg P
@@ -726,46 +637,40 @@ is_integer Fail=f i =>
 is_integer Fail=f an => jump Fail
 is_integer Fail Literal=q => move Literal x | is_integer Fail x
 
-is_integer Fail=f S=rx | allocate Need Regs => is_integer_allocate Fail S Need Regs
+is_integer Fail=f S=x | allocate Need Regs => is_integer_allocate Fail S Need Regs
 
 %macro: is_integer_allocate IsIntegerAllocate -fail_action
 is_integer_allocate f x I I
-is_integer_allocate f r I I
 
 %macro: is_integer IsInteger -fail_action
 is_integer f x
 is_integer f y
-is_integer f r
 
 is_list Fail=f n =>
 is_list Fail Literal=q => move Literal x | is_list Fail x
 is_list Fail=f c => jump Fail
 %macro: is_list IsList -fail_action
-is_list f r
 is_list f x
 %cold
 is_list f y
 %hot
 
-is_nonempty_list Fail=f S=rx | allocate Need Rs => is_nonempty_list_allocate Fail S Need Rs
+is_nonempty_list Fail=f S=x | allocate Need Rs => is_nonempty_list_allocate Fail S Need Rs
 
 %macro:is_nonempty_list_allocate IsNonemptyListAllocate -fail_action -pack
 is_nonempty_list_allocate f x I t
-is_nonempty_list_allocate f r I t
 
-is_nonempty_list F=f r | test_heap I1 I2 => is_non_empty_list_test_heap F r I1 I2
+is_nonempty_list F=f x==0 | test_heap I1 I2 => is_non_empty_list_test_heap F I1 I2
 
 %macro: is_non_empty_list_test_heap IsNonemptyListTestHeap -fail_action -pack
-is_non_empty_list_test_heap f r I t
+is_non_empty_list_test_heap f I t
 
 %macro: is_nonempty_list IsNonemptyList -fail_action
 is_nonempty_list f x
 is_nonempty_list f y
-is_nonempty_list f r
 
 %macro: is_atom IsAtom -fail_action
 is_atom f x
-is_atom f r
 %cold
 is_atom f y
 %hot
@@ -773,7 +678,6 @@ is_atom Fail=f a =>
 is_atom Fail=f niq => jump Fail
 
 %macro: is_float IsFloat -fail_action
-is_float f r
 is_float f x
 %cold
 is_float f y
@@ -787,12 +691,10 @@ is_nil Fail=f qia => jump Fail
 %macro: is_nil IsNil -fail_action
 is_nil f x
 is_nil f y
-is_nil f r
 
 is_binary Fail Literal=q => move Literal x | is_binary Fail x
 is_binary Fail=f c => jump Fail
 %macro: is_binary IsBinary -fail_action
-is_binary f r
 is_binary f x
 %cold
 is_binary f y
@@ -804,7 +706,6 @@ is_bitstr Fail Term => is_bitstring Fail Term
 is_bitstring Fail Literal=q => move Literal x | is_bitstring Fail x
 is_bitstring Fail=f c => jump Fail
 %macro: is_bitstring IsBitstring -fail_action
-is_bitstring f r
 is_bitstring f x
 %cold
 is_bitstring f y
@@ -812,7 +713,6 @@ is_bitstring f y
 
 is_reference Fail=f cq => jump Fail
 %macro: is_reference IsRef -fail_action
-is_reference f r
 is_reference f x
 %cold
 is_reference f y
@@ -820,7 +720,6 @@ is_reference f y
 
 is_pid Fail=f cq => jump Fail
 %macro: is_pid IsPid -fail_action
-is_pid f r
 is_pid f x
 %cold
 is_pid f y
@@ -828,7 +727,6 @@ is_pid f y
 
 is_port Fail=f cq => jump Fail
 %macro: is_port IsPort -fail_action
-is_port f r
 is_port f x
 %cold
 is_port f y
@@ -840,7 +738,6 @@ is_boolean Fail=f ac => jump Fail
 
 %cold
 %macro: is_boolean IsBoolean -fail_action
-is_boolean f r
 is_boolean f x
 is_boolean f y
 %hot
@@ -986,76 +883,76 @@ call_ext_only u==3 u$func:erlang:hibernate/3 => i_hibernate
 %unless USE_VM_PROBES
 
 call_ext Arity u$func:erlang:dt_get_tag/0 => \
-    move a=am_undefined r
+    move a=am_undefined x=0
 call_ext_last Arity u$func:erlang:dt_get_tag/0 D => \
-    move a=am_undefined r | deallocate D | return
+    move a=am_undefined x=0 | deallocate D | return
 call_ext_only Arity u$func:erlang:dt_get_tag/0 => \
-    move a=am_undefined r | return
-
-move Any r | call_ext Arity u$func:erlang:dt_put_tag/1 => \
-    move a=am_undefined r
-move Any r | call_ext_last Arity u$func:erlang:dt_put_tag/1 D => \
-    move a=am_undefined r | deallocate D | return
-move Any r | call_ext_only Arity u$func:erlang:dt_put_tag/1 => \
-    move a=am_undefined r | return
+    move a=am_undefined x=0 | return
+
+move Any x==0 | call_ext Arity u$func:erlang:dt_put_tag/1 => \
+    move a=am_undefined x=0
+move Any x==0 | call_ext_last Arity u$func:erlang:dt_put_tag/1 D => \
+    move a=am_undefined x=0 | deallocate D | return
+move Any x==0 | call_ext_only Arity u$func:erlang:dt_put_tag/1 => \
+    move a=am_undefined x=0 | return
 call_ext Arity u$func:erlang:dt_put_tag/1 => \
-    move a=am_undefined r
+    move a=am_undefined x=0
 call_ext_last Arity u$func:erlang:dt_put_tag/1 D => \
-    move a=am_undefined r | deallocate D | return
+    move a=am_undefined x=0 | deallocate D | return
 call_ext_only Arity u$func:erlang:dt_put_tag/1 => \
-    move a=am_undefined r | return
+    move a=am_undefined x=0 | return
 
 call_ext Arity u$func:erlang:dt_get_tag_data/0 => \
-    move a=am_undefined r
+    move a=am_undefined x=0
 call_ext_last Arity u$func:erlang:dt_get_tag_data/0 D => \
-    move a=am_undefined r | deallocate D | return
+    move a=am_undefined x=0 | deallocate D | return
 call_ext_only Arity u$func:erlang:dt_get_tag_data/0 => \
-    move a=am_undefined r | return
-
-move Any r | call_ext Arity u$func:erlang:dt_spread_tag/1 => \
-    move a=am_true r
-move Any r | call_ext_last Arity u$func:erlang:dt_spread_tag/1 D => \
-    move a=am_true r | deallocate D | return
-move Any r | call_ext_only Arity u$func:erlang:dt_spread_tag/1 => \
-    move a=am_true r | return
+    move a=am_undefined x=0 | return
+
+move Any x==0 | call_ext Arity u$func:erlang:dt_spread_tag/1 => \
+    move a=am_true x=0
+move Any x==0 | call_ext_last Arity u$func:erlang:dt_spread_tag/1 D => \
+    move a=am_true x=0 | deallocate D | return
+move Any x==0 | call_ext_only Arity u$func:erlang:dt_spread_tag/1 => \
+    move a=am_true x=0 | return
 call_ext Arity u$func:erlang:dt_spread_tag/1 => \
-    move a=am_true r
+    move a=am_true x=0
 call_ext_last Arity u$func:erlang:dt_spread_tag/1 D => \
-    move a=am_true r | deallocate D | return
+    move a=am_true x=0 | deallocate D | return
 call_ext_only Arity u$func:erlang:dt_spread_tag/1 => \
-    move a=am_true r | return
-
-move Any r | call_ext Arity u$func:erlang:dt_restore_tag/1 => \
-    move a=am_true r
-move Any r | call_ext_last Arity u$func:erlang:dt_restore_tag/1 D => \
-    move a=am_true r | deallocate D | return
-move Any r | call_ext_only Arity u$func:erlang:dt_restore_tag/1 => \
-    move a=am_true r | return
+    move a=am_true x=0 | return
+
+move Any x==0 | call_ext Arity u$func:erlang:dt_restore_tag/1 => \
+    move a=am_true x=0
+move Any x==0 | call_ext_last Arity u$func:erlang:dt_restore_tag/1 D => \
+    move a=am_true x=0 | deallocate D | return
+move Any x==0 | call_ext_only Arity u$func:erlang:dt_restore_tag/1 => \
+    move a=am_true x=0 | return
 call_ext Arity u$func:erlang:dt_restore_tag/1 => \
-    move a=am_true r
+    move a=am_true x=0
 call_ext_last Arity u$func:erlang:dt_restore_tag/1 D => \
-    move a=am_true r | deallocate D | return
+    move a=am_true x=0 | deallocate D | return
 call_ext_only Arity u$func:erlang:dt_restore_tag/1 => \
-    move a=am_true r | return
-
-move Any r | call_ext Arity u$func:erlang:dt_prepend_vm_tag_data/1 => \
-    move Any r
-move Any r | call_ext_last Arity u$func:erlang:dt_prepend_vm_tag_data/1 D => \
-    move Any r | deallocate D | return
-move Any r | call_ext_only Arity u$func:erlang:dt_prepend_vm_tag_data/1 => \
-    move Any r | return
+    move a=am_true x=0 | return
+
+move Any x==0 | call_ext Arity u$func:erlang:dt_prepend_vm_tag_data/1 => \
+    move Any x=0
+move Any x==0 | call_ext_last Arity u$func:erlang:dt_prepend_vm_tag_data/1 D => \
+    move Any x=0 | deallocate D | return
+move Any x==0 | call_ext_only Arity u$func:erlang:dt_prepend_vm_tag_data/1 => \
+    move Any x=0 | return
 call_ext Arity u$func:erlang:dt_prepend_vm_tag_data/1 =>
 call_ext_last Arity u$func:erlang:dt_prepend_vm_tag_data/1 D => \
     deallocate D | return
 call_ext_only Arity u$func:erlang:dt_prepend_vm_tag_data/1 => \
     return
 
-move Any r | call_ext Arity u$func:erlang:dt_append_vm_tag_data/1 => \
-    move Any r
-move Any r | call_ext_last Arity u$func:erlang:dt_append_vm_tag_data/1 D => \
-    move Any r | deallocate D | return
-move Any r | call_ext_only Arity u$func:erlang:dt_append_vm_tag_data/1 => \
-    move Any r | return
+move Any x==0 | call_ext Arity u$func:erlang:dt_append_vm_tag_data/1 => \
+    move Any x=0
+move Any x==0 | call_ext_last Arity u$func:erlang:dt_append_vm_tag_data/1 D => \
+    move Any x=0 | deallocate D | return
+move Any x==0 | call_ext_only Arity u$func:erlang:dt_append_vm_tag_data/1 => \
+    move Any x=0 | return
 call_ext Arity u$func:erlang:dt_append_vm_tag_data/1 =>
 call_ext_last Arity u$func:erlang:dt_append_vm_tag_data/1 D => \
     deallocate D | return
@@ -1063,7 +960,7 @@ call_ext_only Arity u$func:erlang:dt_append_vm_tag_data/1 => \
     return
 
 # Can happen after one of the transformations above.
-move Discarded r | move Something r => move Something r
+move Discarded x==0 | move Something x==0 => move Something x=0
 
 %endif
 
@@ -1088,9 +985,9 @@ call_ext_only Ar=u Bif=u$is_bif => \
 # with call instructions.
 #
 
-move S=c r | call_ext Ar=u Func=u$is_not_bif => i_move_call_ext S r Func
-move S=c r | call_ext_last Ar=u Func=u$is_not_bif D => i_move_call_ext_last Func D S r
-move S=c r | call_ext_only Ar=u Func=u$is_not_bif => i_move_call_ext_only Func S r 
+move S=c x==0 | call_ext Ar=u Func=u$is_not_bif => i_move_call_ext S Func
+move S=c x==0 | call_ext_last Ar=u Func=u$is_not_bif D => i_move_call_ext_last Func D S
+move S=c x==0 | call_ext_only Ar=u Func=u$is_not_bif => i_move_call_ext_only Func S
 
 call_ext Ar Func        => i_call_ext Func
 call_ext_last Ar Func D => i_call_ext_last Func D
@@ -1117,7 +1014,7 @@ bif0 u$bif:erlang:node/0 Dst=d => node Dst
 
 bif1 Fail Bif=u$bif:erlang:get/1 Src=s Dst=d => i_get Src Dst
 
-bif2 Jump=j u$bif:erlang:element/2 S1=s S2=rxy Dst=d => gen_element(Jump, S1, S2, Dst)
+bif2 Jump=j u$bif:erlang:element/2 S1=s S2=xy Dst=d => gen_element(Jump, S1, S2, Dst)
 
 bif1 p Bif S1 Dst => bif1_body Bif S1 Dst
 
@@ -1127,24 +1024,20 @@ bif2 Fail Bif S1 S2 Dst => i_fetch S1 S2 | i_bif2 Fail Bif Dst
 i_get s d
 
 %macro: self Self
-self r
 self x
 self y
 
 %macro: node Node
-node r
 node x
 %cold
 node y
 %hot
 
-i_fast_element r j I d
-i_fast_element x j I d
-i_fast_element y j I d
+i_fast_element j x I d
+i_fast_element j y I d
 
-i_element r j s d
-i_element x j s d
-i_element y j s d
+i_element j x s d
+i_element j y s d
 
 bif1 f b s d
 bif1_body b s d
@@ -1155,37 +1048,37 @@ i_bif2_body b d
 # Internal calls.
 #
 
-move S=c r | call Ar P=f => i_move_call S r P
-move S=s r | call Ar P=f => move_call S r P
+move S=c x==0 | call Ar P=f => i_move_call S P
+move S=s x==0 | call Ar P=f => move_call S P
 
-i_move_call c r f
+i_move_call c f
 
 %macro:move_call MoveCall -arg_f -size -nonext
-move_call/3
+move_call/2
 
-move_call x r f
-move_call y r f
+move_call x f
+move_call y f
 
-move S=c r | call_last Ar P=f D => i_move_call_last P D S r
-move S r | call_last Ar P=f D => move_call_last S r P D
+move S=c x==0 | call_last Ar P=f D => i_move_call_last P D S
+move S x==0 | call_last Ar P=f D => move_call_last S P D
 
-i_move_call_last f P c r
+i_move_call_last f P c
 
 %macro:move_call_last MoveCallLast -arg_f -nonext -pack
 
-move_call_last/4
-move_call_last x r f Q
-move_call_last y r f Q
+move_call_last/3
+move_call_last x f Q
+move_call_last y f Q
 
-move S=c r | call_only Ar P=f => i_move_call_only P S r
-move S=x r | call_only Ar P=f => move_call_only S r P
+move S=c x==0 | call_only Ar P=f => i_move_call_only P S
+move S=x x==0 | call_only Ar P=f => move_call_only S P
 
-i_move_call_only f c r
+i_move_call_only f c
 
 %macro:move_call_only MoveCallOnly -arg_f -nonext
-move_call_only/3
+move_call_only/2
 
-move_call_only x r f
+move_call_only x f
 
 call Ar Func        => i_call Func
 call_last Ar Func D => i_call_last Func D
@@ -1199,9 +1092,9 @@ i_call_ext e
 i_call_ext_last e P
 i_call_ext_only e
 
-i_move_call_ext c r e
-i_move_call_ext_last e P c r
-i_move_call_ext_only e c r
+i_move_call_ext c e
+i_move_call_ext_last e P c
+i_move_call_ext_only e c
 
 # Fun calls.
 
@@ -1221,7 +1114,6 @@ i_make_fun I t
 %macro: is_function IsFunction -fail_action
 is_function f x
 is_function f y
-is_function f r
 is_function Fail=f c => jump Fail
 
 func_info M F A => i_func_info u M F A
@@ -1233,126 +1125,102 @@ func_info M F A => i_func_info u M F A
 %cold
 bs_start_match2 Fail=f ica X Y D => jump Fail
 bs_start_match2 Fail Bin X Y D => i_bs_start_match2 Bin Fail X Y D
-i_bs_start_match2 r f I I d
 i_bs_start_match2 x f I I d
 i_bs_start_match2 y f I I d
 
 bs_save2 Reg Index => gen_bs_save(Reg, Index)
-i_bs_save2 r I
 i_bs_save2 x I
 
 bs_restore2 Reg Index => gen_bs_restore(Reg, Index)
-i_bs_restore2 r I
 i_bs_restore2 x I
 
 # Matching integers
 bs_match_string Fail Ms Bits Val => i_bs_match_string Ms Fail Bits Val
 
-i_bs_match_string r f I I
 i_bs_match_string x f I I
 
 # Fetching integers from binaries.
-bs_get_integer2 Fail=f Ms=rx Live=u Sz=sq Unit=u Flags=u Dst=d => \
+bs_get_integer2 Fail=f Ms=x Live=u Sz=sq Unit=u Flags=u Dst=d => \
 			gen_get_integer2(Fail, Ms, Live, Sz, Unit, Flags, Dst)
 
-i_bs_get_integer_small_imm r I f I d
 i_bs_get_integer_small_imm x I f I d
-i_bs_get_integer_imm r I I f I d
 i_bs_get_integer_imm x I I f I d
 i_bs_get_integer f I I d
-i_bs_get_integer_8 r f d
 i_bs_get_integer_8 x f d
-i_bs_get_integer_16 r f d
 i_bs_get_integer_16 x f d
-i_bs_get_integer_32 r f I d
 i_bs_get_integer_32 x f I d
 
 # Fetching binaries from binaries.
-bs_get_binary2 Fail=f Ms=rx Live=u Sz=sq Unit=u Flags=u Dst=d => \
+bs_get_binary2 Fail=f Ms=x Live=u Sz=sq Unit=u Flags=u Dst=d => \
 			gen_get_binary2(Fail, Ms, Live, Sz, Unit, Flags, Dst)
 
 %macro: i_bs_get_binary_imm2 BsGetBinaryImm_2 -fail_action -gen_dest
 %macro: i_bs_get_binary2 BsGetBinary_2 -fail_action -gen_dest
 %macro: i_bs_get_binary_all2 BsGetBinaryAll_2 -fail_action -gen_dest
 
-i_bs_get_binary_imm2 f r I I I d
 i_bs_get_binary_imm2 f x I I I d
-i_bs_get_binary2 f r I s I d
 i_bs_get_binary2 f x I s I d
-i_bs_get_binary_all2 f r I I d
 i_bs_get_binary_all2 f x I I d
-i_bs_get_binary_all_reuse r f I
 i_bs_get_binary_all_reuse x f I
 
 # Fetching float from binaries.
-bs_get_float2 Fail=f Ms=rx Live=u Sz=s Unit=u Flags=u Dst=d => \
+bs_get_float2 Fail=f Ms=x Live=u Sz=s Unit=u Flags=u Dst=d => \
 		gen_get_float2(Fail, Ms, Live, Sz, Unit, Flags, Dst)
 
-bs_get_float2 Fail=f Ms=rx Live=u Sz=q Unit=u Flags=u Dst=d => jump Fail
+bs_get_float2 Fail=f Ms=x Live=u Sz=q Unit=u Flags=u Dst=d => jump Fail
 
 %macro: i_bs_get_float2 BsGetFloat2 -fail_action -gen_dest
-i_bs_get_float2 f r I s I d
 i_bs_get_float2 f x I s I d
 
 # Miscellanous
 
-bs_skip_bits2 Fail=f Ms=rx Sz=s Unit=u Flags=u => \
-			gen_skip_bits2(Fail, Ms, Sz, Unit, Flags)
-bs_skip_bits2 Fail=f Ms=rx Sz=q Unit=u Flags=u => \
+bs_skip_bits2 Fail=f Ms=x Sz=sq Unit=u Flags=u => \
 			gen_skip_bits2(Fail, Ms, Sz, Unit, Flags)
 
 %macro: i_bs_skip_bits_imm2 BsSkipBitsImm2 -fail_action
-i_bs_skip_bits_imm2 f r I
 i_bs_skip_bits_imm2 f x I
 
 %macro: i_bs_skip_bits2 BsSkipBits2 -fail_action
-i_bs_skip_bits2 f r x I
-i_bs_skip_bits2 f r y I
 i_bs_skip_bits2 f x x I
-i_bs_skip_bits2 f x r I
 i_bs_skip_bits2 f x y I
 
 %macro: i_bs_skip_bits_all2 BsSkipBitsAll2 -fail_action
-i_bs_skip_bits_all2 f r I
 i_bs_skip_bits_all2 f x I 
 
-bs_test_tail2 Fail=f Ms=rx Bits=u==0 => bs_test_zero_tail2 Fail Ms
-bs_test_tail2 Fail=f Ms=rx Bits=u => bs_test_tail_imm2 Fail Ms Bits
-bs_test_zero_tail2 f r
+bs_test_tail2 Fail=f Ms=x Bits=u==0 => bs_test_zero_tail2 Fail Ms
+bs_test_tail2 Fail=f Ms=x Bits=u => bs_test_tail_imm2 Fail Ms Bits
 bs_test_zero_tail2 f x
-bs_test_tail_imm2 f r I
 bs_test_tail_imm2 f x I
 
 bs_test_unit F Ms Unit=u==8 => bs_test_unit8 F Ms
-bs_test_unit f r I
 bs_test_unit f x I
-bs_test_unit8 f r
 bs_test_unit8 f x
 
-bs_context_to_binary r
+# An y register operand for bs_context_to_binary is rare,
+# but can happen because of inlining.
+
+bs_context_to_binary Y=y => move Y x | bs_context_to_binary x
+
 bs_context_to_binary x
-bs_context_to_binary y
 
 #
 # Utf8/utf16/utf32 support. (R12B-5)
 #
-bs_get_utf8 Fail=f Ms=rx u u Dst=d => i_bs_get_utf8 Ms Fail Dst
-i_bs_get_utf8 r f d
+bs_get_utf8 Fail=f Ms=x u u Dst=d => i_bs_get_utf8 Ms Fail Dst
 i_bs_get_utf8 x f d
 
-bs_skip_utf8 Fail=f Ms=rx u u => i_bs_get_utf8 Ms Fail x
+bs_skip_utf8 Fail=f Ms=x u u => i_bs_get_utf8 Ms Fail x
 
-bs_get_utf16 Fail=f Ms=rx u Flags=u Dst=d => i_bs_get_utf16 Ms Fail Flags Dst
-bs_skip_utf16 Fail=f Ms=rx u Flags=u => i_bs_get_utf16 Ms Fail Flags x
+bs_get_utf16 Fail=f Ms=x u Flags=u Dst=d => i_bs_get_utf16 Ms Fail Flags Dst
+bs_skip_utf16 Fail=f Ms=x u Flags=u => i_bs_get_utf16 Ms Fail Flags x
 
-i_bs_get_utf16 r f I d
 i_bs_get_utf16 x f I d
 
-bs_get_utf32 Fail=f Ms=rx Live=u Flags=u Dst=d => \
+bs_get_utf32 Fail=f Ms=x Live=u Flags=u Dst=d => \
 	bs_get_integer2 Fail Ms Live i=32 u=1 Flags Dst | \
 	i_fetch Dst Ms | \
 	i_bs_validate_unicode_retract Fail
-bs_skip_utf32 Fail=f Ms=rx Live=u Flags=u => \
+bs_skip_utf32 Fail=f Ms=x Live=u Flags=u => \
 	bs_get_integer2 Fail Ms Live i=32 u=1 Flags x | \
 	i_fetch x Ms | \
 	i_bs_validate_unicode_retract Fail
@@ -1379,9 +1247,8 @@ bs_init2 Fail Sz=u Words Regs Flags Dst => \
 bs_init2 Fail Sz Words=u==0 Regs Flags Dst => \
   i_bs_init_fail Sz Fail Regs Dst
 bs_init2 Fail Sz Words Regs Flags Dst => \
-  i_fetch Sz r | i_bs_init_fail_heap Words Fail Regs Dst
+  i_fetch Sz x=0 | i_bs_init_fail_heap Words Fail Regs Dst
 
-i_bs_init_fail r j I d
 i_bs_init_fail x j I d
 i_bs_init_fail y j I d
 
@@ -1402,9 +1269,8 @@ bs_init_bits Fail Sz=u Words Regs Flags Dst =>  i_bs_init_bits_heap Sz Words Reg
 bs_init_bits Fail Sz Words=u==0 Regs Flags Dst => \
   i_bs_init_bits_fail Sz Fail Regs Dst
 bs_init_bits Fail Sz Words Regs Flags Dst => \
-  i_fetch Sz r | i_bs_init_bits_fail_heap Words Fail Regs Dst
+  i_fetch Sz x=0 | i_bs_init_bits_fail_heap Words Fail Regs Dst
 
-i_bs_init_bits_fail r j I d
 i_bs_init_bits_fail x j I d
 i_bs_init_bits_fail y j I d
 
@@ -1577,7 +1443,6 @@ is_map Fail Lit=q | literal_is_map(Lit) =>
 is_map Fail cq => jump Fail
 
 %macro: is_map IsMap -fail_action
-is_map f r
 is_map f x
 is_map f y
 
@@ -1588,35 +1453,25 @@ has_map_fields Fail Src Size Rest=* => \
 
 ## Transform get_map_elements(s) #{ K1 := V1, K2 := V2 }
 
-get_map_elements Fail Src=rxy Size=u==2 Rest=* => \
+get_map_elements Fail Src=xy Size=u==2 Rest=* => \
     gen_get_map_element(Fail, Src, Size, Rest)
 get_map_elements Fail Src Size Rest=* | map_key_sort(Size, Rest) => \
    gen_get_map_elements(Fail, Src, Size, Rest)
 
 i_get_map_elements f s I
 
-i_get_map_element Fail Src=rxy Key=ry Dst => \
+i_get_map_element Fail Src=xy Key=y Dst => \
     move Key x | i_get_map_element Fail Src x Dst
 
 %macro: i_get_map_element_hash GetMapElementHash -fail_action
-i_get_map_element_hash f r c I r
-i_get_map_element_hash f x c I r
-i_get_map_element_hash f y c I r
-i_get_map_element_hash f r c I x
 i_get_map_element_hash f x c I x
 i_get_map_element_hash f y c I x
-i_get_map_element_hash f r c I y
 i_get_map_element_hash f x c I y
 i_get_map_element_hash f y c I y
 
 %macro: i_get_map_element GetMapElement -fail_action
-i_get_map_element f r x r
-i_get_map_element f x x r
-i_get_map_element f y x r
-i_get_map_element f r x x
 i_get_map_element f x x x
 i_get_map_element f y x x
-i_get_map_element f r x y
 i_get_map_element f x x y
 i_get_map_element f y x y
 
@@ -1625,9 +1480,9 @@ i_get_map_element f y x y
 # the i_increment/4 instruction (in bodies, not in guards).
 #
 
-gc_bif2 p Live u$bif:erlang:splus/2 Int=i Reg=d Dst => \
+gc_bif2 p Live u$bif:erlang:splus/2 Int=i Reg=x Dst => \
 	gen_increment(Reg, Int, Live, Dst)
-gc_bif2 p Live u$bif:erlang:splus/2 Reg=d Int=i Dst => \
+gc_bif2 p Live u$bif:erlang:splus/2 Reg=x Int=i Dst => \
 	gen_increment(Reg, Int, Live, Dst)
 
 gc_bif2 p Live u$bif:erlang:sminus/2 Reg=d Int=i Dst | \
@@ -1662,7 +1517,6 @@ gc_bif1 Fail I u$bif:erlang:bnot/1 Src Dst=d => i_int_bnot Fail Src I Dst
 gc_bif1 Fail I u$bif:erlang:sminus/1 Src Dst=d => i_fetch i Src | i_minus Fail I Dst
 gc_bif1 Fail I u$bif:erlang:splus/1 Src Dst=d => i_fetch i Src | i_plus Fail I Dst
 
-i_increment r I I d
 i_increment x I I d
 i_increment y I I d