diff --git a/basis/compiler/cfg/builder/builder.factor b/basis/compiler/cfg/builder/builder.factor
index 7bad44f7a6..fdc0032a10 100755
--- a/basis/compiler/cfg/builder/builder.factor
+++ b/basis/compiler/cfg/builder/builder.factor
@@ -21,8 +21,6 @@ IN: compiler.cfg.builder
 
 ! Convert tree SSA IR to CFG SSA IR.
 
-: stop-iterating ( -- next ) end-basic-block f ;
-
 SYMBOL: procedures
 SYMBOL: current-word
 SYMBOL: current-label
@@ -211,7 +209,7 @@ M: #dispatch emit-node
 ! #call
 M: #call emit-node
     dup word>> dup "intrinsic" word-prop
-    [ emit-intrinsic iterate-next ] [ nip emit-call ] if ;
+    [ emit-intrinsic ] [ nip emit-call ] if ;
 
 ! #call-recursive
 M: #call-recursive emit-node label>> id>> emit-call ;
diff --git a/basis/compiler/cfg/def-use/def-use.factor b/basis/compiler/cfg/def-use/def-use.factor
index 177f172a76..7e97961eb3 100644
--- a/basis/compiler/cfg/def-use/def-use.factor
+++ b/basis/compiler/cfg/def-use/def-use.factor
@@ -18,7 +18,6 @@ M: ##string-nth defs-vregs dst/tmp-vregs ;
 M: ##compare defs-vregs dst/tmp-vregs ;
 M: ##compare-imm defs-vregs dst/tmp-vregs ;
 M: ##compare-float defs-vregs dst/tmp-vregs ;
-M: ##fixnum-overflow defs-vregs temp>> 1array ;
 M: insn defs-vregs drop f ;
 
 M: ##unary uses-vregs src>> 1array ;
diff --git a/basis/compiler/cfg/instructions/instructions.factor b/basis/compiler/cfg/instructions/instructions.factor
index 4c050a3495..9e82851c12 100644
--- a/basis/compiler/cfg/instructions/instructions.factor
+++ b/basis/compiler/cfg/instructions/instructions.factor
@@ -93,10 +93,13 @@ INSN: ##sar-imm < ##binary-imm ;
 INSN: ##not < ##unary ;
 
 ! Overflowing arithmetic
-TUPLE: ##fixnum-overflow < insn src1 src2 temp ;
+TUPLE: ##fixnum-overflow < insn src1 src2 ;
 INSN: ##fixnum-add < ##fixnum-overflow ;
+INSN: ##fixnum-add-tail < ##fixnum-overflow ;
 INSN: ##fixnum-sub < ##fixnum-overflow ;
+INSN: ##fixnum-sub-tail < ##fixnum-overflow ;
 INSN: ##fixnum-mul < ##fixnum-overflow ;
+INSN: ##fixnum-mul-tail < ##fixnum-overflow ;
 
 : ##tag-fixnum ( dst src -- ) tag-bits get ##shl-imm ; inline
 : ##untag-fixnum ( dst src -- ) tag-bits get ##sar-imm ; inline
diff --git a/basis/compiler/cfg/intrinsics/fixnum/fixnum.factor b/basis/compiler/cfg/intrinsics/fixnum/fixnum.factor
index f22623650a..f4a0218565 100644
--- a/basis/compiler/cfg/intrinsics/fixnum/fixnum.factor
+++ b/basis/compiler/cfg/intrinsics/fixnum/fixnum.factor
@@ -3,7 +3,10 @@
 USING: sequences accessors layouts kernel math namespaces
 combinators fry locals
 compiler.tree.propagation.info
-compiler.cfg.stacks compiler.cfg.hats compiler.cfg.instructions
+compiler.cfg.hats
+compiler.cfg.stacks
+compiler.cfg.iterator
+compiler.cfg.instructions
 compiler.cfg.utilities ;
 IN: compiler.cfg.intrinsics.fixnum
 
@@ -65,5 +68,14 @@ IN: compiler.cfg.intrinsics.fixnum
 : emit-fixnum>bignum ( -- )
     ds-pop ^^untag-fixnum ^^integer>bignum ds-push ;
 
-: emit-fixnum-overflow-op ( quot -- )
-    [ 2inputs i 1 ##inc-d ] dip call begin-basic-block ; inline
+: emit-fixnum-overflow-op ( quot quot-tail -- next )
+    [ 2inputs 1 ##inc-d ] 2dip
+    tail-call? [
+        ##epilogue
+        nip call
+        stop-iterating
+    ] [
+        drop call
+        begin-basic-block
+        iterate-next
+    ] if ; inline
diff --git a/basis/compiler/cfg/intrinsics/intrinsics.factor b/basis/compiler/cfg/intrinsics/intrinsics.factor
index 7a073f56b0..50d5525f2d 100644
--- a/basis/compiler/cfg/intrinsics/intrinsics.factor
+++ b/basis/compiler/cfg/intrinsics/intrinsics.factor
@@ -8,7 +8,8 @@ compiler.cfg.intrinsics.alien
 compiler.cfg.intrinsics.allot
 compiler.cfg.intrinsics.fixnum
 compiler.cfg.intrinsics.float
-compiler.cfg.intrinsics.slots ;
+compiler.cfg.intrinsics.slots
+compiler.cfg.iterator ;
 QUALIFIED: kernel
 QUALIFIED: arrays
 QUALIFIED: byte-arrays
@@ -87,63 +88,63 @@ IN: compiler.cfg.intrinsics
         alien.accessors:set-alien-double
     } [ t "intrinsic" set-word-prop ] each ;
 
-: emit-intrinsic ( node word -- )
+: emit-intrinsic ( node word -- node/f )
     {
-        { \ kernel.private:tag [ drop emit-tag ] }
-        { \ math.private:fixnum+ [ drop [ ##fixnum-add ] emit-fixnum-overflow-op ] }
-        { \ math.private:fixnum- [ drop [ ##fixnum-sub ] emit-fixnum-overflow-op ] }
-        { \ math.private:fixnum* [ drop [ ##fixnum-mul ] emit-fixnum-overflow-op ] }
-        { \ math.private:fixnum+fast [ [ ^^add ] [ ^^add-imm ] emit-fixnum-op ] }
-        { \ math.private:fixnum-fast [ [ ^^sub ] [ ^^sub-imm ] emit-fixnum-op ] }
-        { \ math.private:fixnum-bitand [ [ ^^and ] [ ^^and-imm ] emit-fixnum-op ] }
-        { \ math.private:fixnum-bitor [ [ ^^or ] [ ^^or-imm ] emit-fixnum-op ] }
-        { \ math.private:fixnum-bitxor [ [ ^^xor ] [ ^^xor-imm ] emit-fixnum-op ] }
-        { \ math.private:fixnum-shift-fast [ emit-fixnum-shift-fast ] }
-        { \ math.private:fixnum-bitnot [ drop emit-fixnum-bitnot ] }
-        { \ math.private:fixnum*fast [ emit-fixnum*fast ] }
-        { \ math.private:fixnum< [ cc< emit-fixnum-comparison ] }
-        { \ math.private:fixnum<= [ cc<= emit-fixnum-comparison ] }
-        { \ math.private:fixnum>= [ cc>= emit-fixnum-comparison ] }
-        { \ math.private:fixnum> [ cc> emit-fixnum-comparison ] }
-        { \ kernel:eq? [ cc= emit-fixnum-comparison ] }
-        { \ math.private:bignum>fixnum [ drop emit-bignum>fixnum ] }
-        { \ math.private:fixnum>bignum [ drop emit-fixnum>bignum ] }
-        { \ math.private:float+ [ drop [ ^^add-float ] emit-float-op ] }
-        { \ math.private:float- [ drop [ ^^sub-float ] emit-float-op ] }
-        { \ math.private:float* [ drop [ ^^mul-float ] emit-float-op ] }
-        { \ math.private:float/f [ drop [ ^^div-float ] emit-float-op ] }
-        { \ math.private:float< [ drop cc< emit-float-comparison ] }
-        { \ math.private:float<= [ drop cc<= emit-float-comparison ] }
-        { \ math.private:float>= [ drop cc>= emit-float-comparison ] }
-        { \ math.private:float> [ drop cc> emit-float-comparison ] }
-        { \ math.private:float= [ drop cc= emit-float-comparison ] }
-        { \ math.private:float>fixnum [ drop emit-float>fixnum ] }
-        { \ math.private:fixnum>float [ drop emit-fixnum>float ] }
-        { \ slots.private:slot [ emit-slot ] }
-        { \ slots.private:set-slot [ emit-set-slot ] }
-        { \ strings.private:string-nth [ drop emit-string-nth ] }
-        { \ classes.tuple.private:<tuple-boa> [ emit-<tuple-boa> ] }
-        { \ arrays:<array> [ emit-<array> ] }
-        { \ byte-arrays:<byte-array> [ emit-<byte-array> ] }
-        { \ math.private:<complex> [ emit-simple-allot ] }
-        { \ math.private:<ratio> [ emit-simple-allot ] }
-        { \ kernel:<wrapper> [ emit-simple-allot ] }
-        { \ alien.accessors:alien-unsigned-1 [ 1 emit-alien-unsigned-getter ] }
-        { \ alien.accessors:set-alien-unsigned-1 [ 1 emit-alien-integer-setter ] }
-        { \ alien.accessors:alien-signed-1 [ 1 emit-alien-signed-getter ] }
-        { \ alien.accessors:set-alien-signed-1 [ 1 emit-alien-integer-setter ] }
-        { \ alien.accessors:alien-unsigned-2 [ 2 emit-alien-unsigned-getter ] }
-        { \ alien.accessors:set-alien-unsigned-2 [ 2 emit-alien-integer-setter ] }
-        { \ alien.accessors:alien-signed-2 [ 2 emit-alien-signed-getter ] }
-        { \ alien.accessors:set-alien-signed-2 [ 2 emit-alien-integer-setter ] }
-        { \ alien.accessors:alien-unsigned-4 [ 4 emit-alien-unsigned-getter ] }
-        { \ alien.accessors:set-alien-unsigned-4 [ 4 emit-alien-integer-setter ] }
-        { \ alien.accessors:alien-signed-4 [ 4 emit-alien-signed-getter ] }
-        { \ alien.accessors:set-alien-signed-4 [ 4 emit-alien-integer-setter ] }
-        { \ alien.accessors:alien-cell [ emit-alien-cell-getter ] }
-        { \ alien.accessors:set-alien-cell [ emit-alien-cell-setter ] }
-        { \ alien.accessors:alien-float [ single-float-regs emit-alien-float-getter ] }
-        { \ alien.accessors:set-alien-float [ single-float-regs emit-alien-float-setter ] }
-        { \ alien.accessors:alien-double [ double-float-regs emit-alien-float-getter ] }
-        { \ alien.accessors:set-alien-double [ double-float-regs emit-alien-float-setter ] }
+        { \ kernel.private:tag [ drop emit-tag iterate-next ] }
+        { \ math.private:fixnum+ [ drop [ ##fixnum-add ] [ ##fixnum-add-tail ] emit-fixnum-overflow-op ] }
+        { \ math.private:fixnum- [ drop [ ##fixnum-sub ] [ ##fixnum-sub-tail ] emit-fixnum-overflow-op ] }
+        { \ math.private:fixnum* [ drop [ ##fixnum-mul ] [ ##fixnum-mul-tail ] emit-fixnum-overflow-op ] }
+        { \ math.private:fixnum+fast [ [ ^^add ] [ ^^add-imm ] emit-fixnum-op iterate-next ] }
+        { \ math.private:fixnum-fast [ [ ^^sub ] [ ^^sub-imm ] emit-fixnum-op iterate-next ] }
+        { \ math.private:fixnum-bitand [ [ ^^and ] [ ^^and-imm ] emit-fixnum-op iterate-next ] }
+        { \ math.private:fixnum-bitor [ [ ^^or ] [ ^^or-imm ] emit-fixnum-op iterate-next ] }
+        { \ math.private:fixnum-bitxor [ [ ^^xor ] [ ^^xor-imm ] emit-fixnum-op iterate-next ] }
+        { \ math.private:fixnum-shift-fast [ emit-fixnum-shift-fast iterate-next ] }
+        { \ math.private:fixnum-bitnot [ drop emit-fixnum-bitnot iterate-next ] }
+        { \ math.private:fixnum*fast [ emit-fixnum*fast iterate-next ] }
+        { \ math.private:fixnum< [ cc< emit-fixnum-comparison iterate-next ] }
+        { \ math.private:fixnum<= [ cc<= emit-fixnum-comparison iterate-next ] }
+        { \ math.private:fixnum>= [ cc>= emit-fixnum-comparison iterate-next ] }
+        { \ math.private:fixnum> [ cc> emit-fixnum-comparison iterate-next ] }
+        { \ kernel:eq? [ cc= emit-fixnum-comparison iterate-next ] }
+        { \ math.private:bignum>fixnum [ drop emit-bignum>fixnum iterate-next ] }
+        { \ math.private:fixnum>bignum [ drop emit-fixnum>bignum iterate-next ] }
+        { \ math.private:float+ [ drop [ ^^add-float ] emit-float-op iterate-next ] }
+        { \ math.private:float- [ drop [ ^^sub-float ] emit-float-op iterate-next ] }
+        { \ math.private:float* [ drop [ ^^mul-float ] emit-float-op iterate-next ] }
+        { \ math.private:float/f [ drop [ ^^div-float ] emit-float-op iterate-next ] }
+        { \ math.private:float< [ drop cc< emit-float-comparison iterate-next ] }
+        { \ math.private:float<= [ drop cc<= emit-float-comparison iterate-next ] }
+        { \ math.private:float>= [ drop cc>= emit-float-comparison iterate-next ] }
+        { \ math.private:float> [ drop cc> emit-float-comparison iterate-next ] }
+        { \ math.private:float= [ drop cc= emit-float-comparison iterate-next ] }
+        { \ math.private:float>fixnum [ drop emit-float>fixnum iterate-next ] }
+        { \ math.private:fixnum>float [ drop emit-fixnum>float iterate-next ] }
+        { \ slots.private:slot [ emit-slot iterate-next ] }
+        { \ slots.private:set-slot [ emit-set-slot iterate-next ] }
+        { \ strings.private:string-nth [ drop emit-string-nth iterate-next ] }
+        { \ classes.tuple.private:<tuple-boa> [ emit-<tuple-boa> iterate-next ] }
+        { \ arrays:<array> [ emit-<array> iterate-next ] }
+        { \ byte-arrays:<byte-array> [ emit-<byte-array> iterate-next ] }
+        { \ math.private:<complex> [ emit-simple-allot iterate-next ] }
+        { \ math.private:<ratio> [ emit-simple-allot iterate-next ] }
+        { \ kernel:<wrapper> [ emit-simple-allot iterate-next ] }
+        { \ alien.accessors:alien-unsigned-1 [ 1 emit-alien-unsigned-getter iterate-next ] }
+        { \ alien.accessors:set-alien-unsigned-1 [ 1 emit-alien-integer-setter iterate-next ] }
+        { \ alien.accessors:alien-signed-1 [ 1 emit-alien-signed-getter iterate-next ] }
+        { \ alien.accessors:set-alien-signed-1 [ 1 emit-alien-integer-setter iterate-next ] }
+        { \ alien.accessors:alien-unsigned-2 [ 2 emit-alien-unsigned-getter iterate-next ] }
+        { \ alien.accessors:set-alien-unsigned-2 [ 2 emit-alien-integer-setter iterate-next ] }
+        { \ alien.accessors:alien-signed-2 [ 2 emit-alien-signed-getter iterate-next ] }
+        { \ alien.accessors:set-alien-signed-2 [ 2 emit-alien-integer-setter iterate-next ] }
+        { \ alien.accessors:alien-unsigned-4 [ 4 emit-alien-unsigned-getter iterate-next ] }
+        { \ alien.accessors:set-alien-unsigned-4 [ 4 emit-alien-integer-setter iterate-next ] }
+        { \ alien.accessors:alien-signed-4 [ 4 emit-alien-signed-getter iterate-next ] }
+        { \ alien.accessors:set-alien-signed-4 [ 4 emit-alien-integer-setter iterate-next ] }
+        { \ alien.accessors:alien-cell [ emit-alien-cell-getter iterate-next ] }
+        { \ alien.accessors:set-alien-cell [ emit-alien-cell-setter iterate-next ] }
+        { \ alien.accessors:alien-float [ single-float-regs emit-alien-float-getter iterate-next ] }
+        { \ alien.accessors:set-alien-float [ single-float-regs emit-alien-float-setter iterate-next ] }
+        { \ alien.accessors:alien-double [ double-float-regs emit-alien-float-getter iterate-next ] }
+        { \ alien.accessors:set-alien-double [ double-float-regs emit-alien-float-setter iterate-next ] }
     } case ;
diff --git a/basis/compiler/cfg/stack-frame/stack-frame.factor b/basis/compiler/cfg/stack-frame/stack-frame.factor
index ade2e8ac5e..d545b6d15c 100644
--- a/basis/compiler/cfg/stack-frame/stack-frame.factor
+++ b/basis/compiler/cfg/stack-frame/stack-frame.factor
@@ -37,6 +37,9 @@ M: insn compute-stack-frame*
 \ ##fixnum-add t frame-required? set-word-prop
 \ ##fixnum-sub t frame-required? set-word-prop
 \ ##fixnum-mul t frame-required? set-word-prop
+\ ##fixnum-add-tail f frame-required? set-word-prop
+\ ##fixnum-sub-tail f frame-required? set-word-prop
+\ ##fixnum-mul-tail f frame-required? set-word-prop
 
 : compute-stack-frame ( insns -- )
     frame-required? off
diff --git a/basis/compiler/cfg/utilities/utilities.factor b/basis/compiler/cfg/utilities/utilities.factor
index cef14d06e4..99a138a763 100644
--- a/basis/compiler/cfg/utilities/utilities.factor
+++ b/basis/compiler/cfg/utilities/utilities.factor
@@ -33,5 +33,7 @@ IN: compiler.cfg.utilities
     building off
     basic-block off ;
 
+: stop-iterating ( -- next ) end-basic-block f ;
+
 : emit-primitive ( node -- )
     word>> ##call ##branch begin-basic-block ;
diff --git a/basis/compiler/codegen/codegen.factor b/basis/compiler/codegen/codegen.factor
index f26c034e9f..b66b6a11c7 100644
--- a/basis/compiler/codegen/codegen.factor
+++ b/basis/compiler/codegen/codegen.factor
@@ -156,14 +156,15 @@ M: ##shr-imm generate-insn dst/src1/src2 %shr-imm ;
 M: ##sar-imm generate-insn dst/src1/src2 %sar-imm ;
 M: ##not     generate-insn dst/src       %not     ;
 
-: src1/src2/temp ( insn -- src1 src2 temp )
-    [ src1>> register ]
-    [ src2>> register ]
-    [ temp>> register ] tri ; inline
+: src1/src2 ( insn -- src1 src2 )
+    [ src1>> register ] [ src2>> register ] bi ; inline
 
-M: ##fixnum-add generate-insn src1/src2/temp %fixnum-add ;
-M: ##fixnum-sub generate-insn src1/src2/temp %fixnum-sub ;
-M: ##fixnum-mul generate-insn src1/src2/temp %fixnum-mul ;
+M: ##fixnum-add generate-insn src1/src2 %fixnum-add ;
+M: ##fixnum-add-tail generate-insn src1/src2 %fixnum-add-tail ;
+M: ##fixnum-sub generate-insn src1/src2 %fixnum-sub ;
+M: ##fixnum-sub-tail generate-insn src1/src2 %fixnum-sub-tail ;
+M: ##fixnum-mul generate-insn src1/src2 %fixnum-mul ;
+M: ##fixnum-mul-tail generate-insn src1/src2 %fixnum-mul-tail ;
 
 : dst/src/temp ( insn -- dst src temp )
     [ dst/src ] [ temp>> register ] bi ; inline
diff --git a/basis/cpu/architecture/architecture.factor b/basis/cpu/architecture/architecture.factor
index 0f867e9027..2fdad0132a 100644
--- a/basis/cpu/architecture/architecture.factor
+++ b/basis/cpu/architecture/architecture.factor
@@ -77,9 +77,12 @@ HOOK: %shr-imm cpu ( dst src1 src2 -- )
 HOOK: %sar-imm cpu ( dst src1 src2 -- )
 HOOK: %not     cpu ( dst src -- )
 
-HOOK: %fixnum-add cpu ( src1 src2 temp -- )
-HOOK: %fixnum-sub cpu ( src1 src2 temp -- )
-HOOK: %fixnum-mul cpu ( src1 src2 temp -- )
+HOOK: %fixnum-add cpu ( src1 src2 -- )
+HOOK: %fixnum-add-tail cpu ( src1 src2 -- )
+HOOK: %fixnum-sub cpu ( src1 src2 -- )
+HOOK: %fixnum-sub-tail cpu ( src1 src2 -- )
+HOOK: %fixnum-mul cpu ( src1 src2 -- )
+HOOK: %fixnum-mul-tail cpu ( src1 src2 -- )
 
 HOOK: %integer>bignum cpu ( dst src temp -- )
 HOOK: %bignum>integer cpu ( dst src temp -- )
diff --git a/basis/cpu/x86/32/32.factor b/basis/cpu/x86/32/32.factor
index 0972ff5592..ecf92b7ede 100644
--- a/basis/cpu/x86/32/32.factor
+++ b/basis/cpu/x86/32/32.factor
@@ -48,6 +48,8 @@ M: x86.32 %alien-global 0 [] MOV rc-absolute-cell rel-dlsym ;
 
 M: x86.32 %alien-invoke (CALL) rel-dlsym ;
 
+M: x86.32 %alien-invoke-tail (JMP) rel-dlsym ;
+
 M: x86.32 struct-small-enough? ( size -- ? )
     heap-size { 1 2 4 8 } member?
     os { linux netbsd solaris } member? not and ;
diff --git a/basis/cpu/x86/64/64.factor b/basis/cpu/x86/64/64.factor
index 9233af2a93..b6c76a78fd 100644
--- a/basis/cpu/x86/64/64.factor
+++ b/basis/cpu/x86/64/64.factor
@@ -168,6 +168,11 @@ M: x86.64 %alien-invoke
     rc-absolute-cell rel-dlsym
     R11 CALL ;
 
+M: x86.64 %alien-invoke-tail
+    R11 0 MOV
+    rc-absolute-cell rel-dlsym
+    R11 JMP ;
+
 M: x86.64 %prepare-alien-indirect ( -- )
     "unbox_alien" f %alien-invoke
     RBP RAX MOV ;
diff --git a/basis/cpu/x86/x86.factor b/basis/cpu/x86/x86.factor
index 0feab43545..104a1f155b 100644
--- a/basis/cpu/x86/x86.factor
+++ b/basis/cpu/x86/x86.factor
@@ -108,22 +108,42 @@ M: x86 %not     drop NOT ;
         ]
     } cond ;
 
-:: overflow-template ( src1 src2 temp insn func -- )
-    <label> "end" set
-    temp src1 MOV
-    temp src2 insn call
-    ds-reg [] temp MOV
-    "end" get JNO
+HOOK: %alien-invoke-tail cpu ( func dll -- )
+
+:: overflow-template ( src1 src2 insn inverse func -- )
+    <label> "no-overflow" set
+    src1 src2 insn call
+    ds-reg [] src1 MOV
+    "no-overflow" get JNO
+    src1 src2 inverse call
     src1 src2 move>args
     %prepare-alien-invoke
     func f %alien-invoke
-    "end" resolve-label ;
+    "no-overflow" resolve-label ; inline
 
-M: x86 %fixnum-add ( src1 src2 temp -- )
-    [ ADD ] "overflow_fixnum_add" overflow-template ;
+:: overflow-template-tail ( src1 src2 insn inverse func -- )
+    <label> "no-overflow" set
+    src1 src2 insn call
+    "no-overflow" get JNO
+    src1 src2 inverse call
+    src1 src2 move>args
+    %prepare-alien-invoke
+    func f %alien-invoke-tail
+    "no-overflow" resolve-label
+    ds-reg [] src1 MOV
+    0 RET ; inline
 
-M: x86 %fixnum-sub ( src1 src2 temp -- )
-    [ SUB ] "overflow_fixnum_subtract" overflow-template ;
+M: x86 %fixnum-add ( src1 src2 -- )
+    [ ADD ] [ SUB ] "overflow_fixnum_add" overflow-template ;
+
+M: x86 %fixnum-add-tail ( src1 src2 -- )
+    [ ADD ] [ SUB ] "overflow_fixnum_add" overflow-template-tail ;
+
+M: x86 %fixnum-sub ( src1 src2 -- )
+    [ SUB ] [ ADD ] "overflow_fixnum_subtract" overflow-template ;
+
+M: x86 %fixnum-sub-tail ( src1 src2 -- )
+    [ SUB ] [ ADD ] "overflow_fixnum_subtract" overflow-template-tail ;
 
 : bignum@ ( reg n -- op )
     cells bignum tag-number - [+] ; inline