diff --git a/src/test/ref/examples/eightqueens/eightqueens-recursive.log b/src/test/ref/examples/eightqueens/eightqueens-recursive.log
index 22489cf96..3265c47eb 100644
--- a/src/test/ref/examples/eightqueens/eightqueens-recursive.log
+++ b/src/test/ref/examples/eightqueens/eightqueens-recursive.log
@@ -22,8 +22,8 @@ Eliminating unused variable with no statement print::$5
Eliminating unused variable with no statement print::$8
Eliminating unused variable with no statement print::$9
Converting PHI-variable modified inside __stackcall procedure queen() to load/store count
-Calling convention STACK_CALL adding prepare/execute/finalize for call queen 1
-Calling convention STACK_CALL adding prepare/execute/finalize for call queen queen::$4
+Calling convention __stackcall adding prepare/execute/finalize for call queen 1
+Calling convention __stackcall adding prepare/execute/finalize for call queen queen::$4
Calling convention STACK_CALL replacing param(queen::row) with stackidx(byte,queen::OFFSET_STACK_ROW)
Calling convention STACK_CALL adding stack push stackpush(byte) = 1
Calling convention STACK_CALL adding stack push stackpush(byte) = queen::$4
diff --git a/src/test/ref/procedure-callingconvention-stack-0.log b/src/test/ref/procedure-callingconvention-stack-0.log
index eef196051..5091f81e2 100644
--- a/src/test/ref/procedure-callingconvention-stack-0.log
+++ b/src/test/ref/procedure-callingconvention-stack-0.log
@@ -1,4 +1,4 @@
-Calling convention STACK_CALL adding prepare/execute/finalize for main::$0 = call plus '0' 7
+Calling convention __stackcall adding prepare/execute/finalize for main::$0 = call plus '0' 7
Calling convention STACK_CALL replacing param(plus::a) with stackidx(byte,plus::OFFSET_STACK_A)
Calling convention STACK_CALL replacing param(plus::b) with stackidx(byte,plus::OFFSET_STACK_B)
Calling convention STACK_CALL adding stack return stackidx(byte,plus::OFFSET_STACK_RETURN) = plus::return
diff --git a/src/test/ref/procedure-callingconvention-stack-1.log b/src/test/ref/procedure-callingconvention-stack-1.log
index eef196051..5091f81e2 100644
--- a/src/test/ref/procedure-callingconvention-stack-1.log
+++ b/src/test/ref/procedure-callingconvention-stack-1.log
@@ -1,4 +1,4 @@
-Calling convention STACK_CALL adding prepare/execute/finalize for main::$0 = call plus '0' 7
+Calling convention __stackcall adding prepare/execute/finalize for main::$0 = call plus '0' 7
Calling convention STACK_CALL replacing param(plus::a) with stackidx(byte,plus::OFFSET_STACK_A)
Calling convention STACK_CALL replacing param(plus::b) with stackidx(byte,plus::OFFSET_STACK_B)
Calling convention STACK_CALL adding stack return stackidx(byte,plus::OFFSET_STACK_RETURN) = plus::return
diff --git a/src/test/ref/procedure-callingconvention-stack-10.log b/src/test/ref/procedure-callingconvention-stack-10.log
index bb5b202ff..e5fe9aef4 100644
--- a/src/test/ref/procedure-callingconvention-stack-10.log
+++ b/src/test/ref/procedure-callingconvention-stack-10.log
@@ -1,9 +1,9 @@
Inlined call call __init
Eliminating unused variable with no statement main::$1
Converting PHI-variable modified inside __stackcall procedure main() to load/store idx
-Calling convention STACK_CALL adding prepare/execute/finalize for { main::$1_x, main::$1_y } = call get main::i
-Calling convention STACK_CALL adding prepare/execute/finalize for call print main::p_x main::p_y
-Calling convention STACK_CALL adding prepare/execute/finalize for call main
+Calling convention __stackcall adding prepare/execute/finalize for { main::$1_x, main::$1_y } = call get main::i
+Calling convention __stackcall adding prepare/execute/finalize for call print main::p_x main::p_y
+Calling convention __stackcall adding prepare/execute/finalize for call main
Calling convention STACK_CALL replacing param(get::i) with stackidx(byte,get::OFFSET_STACK_I)
Calling convention STACK_CALL replacing param(print::p_x) with stackidx(byte,print::OFFSET_STACK_P_X)
Calling convention STACK_CALL replacing param(print::p_y) with stackidx(byte,print::OFFSET_STACK_P_Y)
diff --git a/src/test/ref/procedure-callingconvention-stack-11.log b/src/test/ref/procedure-callingconvention-stack-11.log
index df4eb7111..40e27b6c5 100644
--- a/src/test/ref/procedure-callingconvention-stack-11.log
+++ b/src/test/ref/procedure-callingconvention-stack-11.log
@@ -3,9 +3,9 @@ Eliminating unused variable with no statement main::$1
Eliminating unused variable with no statement main::$1_p1
Eliminating unused variable with no statement main::$1_p2
Converting PHI-variable modified inside __stackcall procedure main() to load/store idx
-Calling convention STACK_CALL adding prepare/execute/finalize for { { main::$1_p1_x, main::$1_p1_y }, { main::$1_p2_x, main::$1_p2_y } } = call get main::i
-Calling convention STACK_CALL adding prepare/execute/finalize for call print main::v_p1_x main::v_p1_y main::v_p2_x main::v_p2_y
-Calling convention STACK_CALL adding prepare/execute/finalize for call main
+Calling convention __stackcall adding prepare/execute/finalize for { { main::$1_p1_x, main::$1_p1_y }, { main::$1_p2_x, main::$1_p2_y } } = call get main::i
+Calling convention __stackcall adding prepare/execute/finalize for call print main::v_p1_x main::v_p1_y main::v_p2_x main::v_p2_y
+Calling convention __stackcall adding prepare/execute/finalize for call main
Calling convention STACK_CALL replacing param(get::i) with stackidx(byte,get::OFFSET_STACK_I)
Calling convention STACK_CALL replacing param(print::v_p1_x) with stackidx(byte,print::OFFSET_STACK_V_P1_X)
Calling convention STACK_CALL replacing param(print::v_p1_y) with stackidx(byte,print::OFFSET_STACK_V_P1_Y)
diff --git a/src/test/ref/procedure-callingconvention-stack-12.log b/src/test/ref/procedure-callingconvention-stack-12.log
index f3aaf1bf6..89b742c17 100644
--- a/src/test/ref/procedure-callingconvention-stack-12.log
+++ b/src/test/ref/procedure-callingconvention-stack-12.log
@@ -1,8 +1,8 @@
Inlined call call __init
Converting PHI-variable modified inside __stackcall procedure main() to load/store idx
-Calling convention STACK_CALL adding prepare/execute/finalize for call print main::str 1
-Calling convention STACK_CALL adding prepare/execute/finalize for call print main::str1 2
-Calling convention STACK_CALL adding prepare/execute/finalize for call main
+Calling convention __stackcall adding prepare/execute/finalize for call print main::str 1
+Calling convention __stackcall adding prepare/execute/finalize for call print main::str1 2
+Calling convention __stackcall adding prepare/execute/finalize for call main
Calling convention STACK_CALL replacing param(print::str) with stackidx(byte*,print::OFFSET_STACK_STR)
Calling convention STACK_CALL replacing param(print::spacing) with stackidx(byte,print::OFFSET_STACK_SPACING)
Calling convention STACK_CALL adding stack push stackpush(byte*) = main::str
diff --git a/src/test/ref/procedure-callingconvention-stack-13.log b/src/test/ref/procedure-callingconvention-stack-13.log
index c8ea15b1e..1bc7d7970 100644
--- a/src/test/ref/procedure-callingconvention-stack-13.log
+++ b/src/test/ref/procedure-callingconvention-stack-13.log
@@ -1,5 +1,5 @@
-Calling convention STACK_CALL adding prepare/execute/finalize for main::$0 = call pow2 6
-Calling convention STACK_CALL adding prepare/execute/finalize for pow2::$2 = call pow2 pow2::$1
+Calling convention __stackcall adding prepare/execute/finalize for main::$0 = call pow2 6
+Calling convention __stackcall adding prepare/execute/finalize for pow2::$2 = call pow2 pow2::$1
Calling convention STACK_CALL replacing param(pow2::n) with stackidx(byte,pow2::OFFSET_STACK_N)
Calling convention STACK_CALL adding stack return stackidx(byte,pow2::OFFSET_STACK_RETURN) = pow2::return
Calling convention STACK_CALL adding stack pull main::$0 = stackpull(byte)
diff --git a/src/test/ref/procedure-callingconvention-stack-2.log b/src/test/ref/procedure-callingconvention-stack-2.log
index 34bff33fa..1dd072e62 100644
--- a/src/test/ref/procedure-callingconvention-stack-2.log
+++ b/src/test/ref/procedure-callingconvention-stack-2.log
@@ -1,4 +1,4 @@
-Calling convention STACK_CALL adding prepare/execute/finalize for main::$0 = call plus $1234 $2345
+Calling convention __stackcall adding prepare/execute/finalize for main::$0 = call plus $1234 $2345
Calling convention STACK_CALL replacing param(plus::a) with stackidx(word,plus::OFFSET_STACK_A)
Calling convention STACK_CALL replacing param(plus::b) with stackidx(word,plus::OFFSET_STACK_B)
Calling convention STACK_CALL adding stack return stackidx(word,plus::OFFSET_STACK_RETURN) = plus::return
diff --git a/src/test/ref/procedure-callingconvention-stack-3.log b/src/test/ref/procedure-callingconvention-stack-3.log
index 16e43bc74..1a2a11d06 100644
--- a/src/test/ref/procedure-callingconvention-stack-3.log
+++ b/src/test/ref/procedure-callingconvention-stack-3.log
@@ -1,4 +1,4 @@
-Calling convention STACK_CALL adding prepare/execute/finalize for main::$0 = call plus '0' 7
+Calling convention __stackcall adding prepare/execute/finalize for main::$0 = call plus '0' 7
Calling convention STACK_CALL replacing param(plus::a) with stackidx(word,plus::OFFSET_STACK_A)
Calling convention STACK_CALL replacing param(plus::b) with stackidx(word,plus::OFFSET_STACK_B)
Calling convention STACK_CALL adding stack return stackidx(word,plus::OFFSET_STACK_RETURN) = plus::return
diff --git a/src/test/ref/procedure-callingconvention-stack-4.log b/src/test/ref/procedure-callingconvention-stack-4.log
index fc04cfd65..d9c19d472 100644
--- a/src/test/ref/procedure-callingconvention-stack-4.log
+++ b/src/test/ref/procedure-callingconvention-stack-4.log
@@ -1,6 +1,6 @@
Inlined call call __init
Converting PHI-variable modified inside __stackcall procedure plus() to load/store i
-Calling convention STACK_CALL adding prepare/execute/finalize for main::$1 = call plus '0' main::v
+Calling convention __stackcall adding prepare/execute/finalize for main::$1 = call plus '0' main::v
Calling convention STACK_CALL replacing param(plus::a) with stackidx(byte,plus::OFFSET_STACK_A)
Calling convention STACK_CALL replacing param(plus::b) with stackidx(byte,plus::OFFSET_STACK_B)
Calling convention STACK_CALL adding stack return stackidx(byte,plus::OFFSET_STACK_RETURN) = plus::return
diff --git a/src/test/ref/procedure-callingconvention-stack-5.log b/src/test/ref/procedure-callingconvention-stack-5.log
index 9709b0d9e..3fd4a8588 100644
--- a/src/test/ref/procedure-callingconvention-stack-5.log
+++ b/src/test/ref/procedure-callingconvention-stack-5.log
@@ -1,7 +1,7 @@
Inlined call call __init
Converting PHI-variable modified inside __stackcall procedure next() to load/store current
-Calling convention STACK_CALL adding prepare/execute/finalize for main::$0 = call next
-Calling convention STACK_CALL adding prepare/execute/finalize for main::$1 = call next
+Calling convention __stackcall adding prepare/execute/finalize for main::$0 = call next
+Calling convention __stackcall adding prepare/execute/finalize for main::$1 = call next
Calling convention STACK_CALL adding stack return stackidx(signed word,next::OFFSET_STACK_RETURN) = next::return
Calling convention STACK_CALL adding stack pull main::$0 = stackpull(signed word)
Calling convention STACK_CALL adding stack pull main::$1 = stackpull(signed word)
diff --git a/src/test/ref/procedure-callingconvention-stack-7.log b/src/test/ref/procedure-callingconvention-stack-7.log
index f53079464..38b718e72 100644
--- a/src/test/ref/procedure-callingconvention-stack-7.log
+++ b/src/test/ref/procedure-callingconvention-stack-7.log
@@ -1,5 +1,5 @@
-Calling convention STACK_CALL adding prepare/execute/finalize for call printline
-Calling convention STACK_CALL adding prepare/execute/finalize for call main
+Calling convention __stackcall adding prepare/execute/finalize for call printline
+Calling convention __stackcall adding prepare/execute/finalize for call main
CONTROL FLOW GRAPH SSA
diff --git a/src/test/ref/procedure-callingconvention-stack-8.log b/src/test/ref/procedure-callingconvention-stack-8.log
index e3274480f..ac4747f5c 100644
--- a/src/test/ref/procedure-callingconvention-stack-8.log
+++ b/src/test/ref/procedure-callingconvention-stack-8.log
@@ -1,7 +1,7 @@
Inlined call call __init
Converting PHI-variable modified inside __stackcall procedure main() to load/store val
-Calling convention STACK_CALL adding prepare/execute/finalize for call printline
-Calling convention STACK_CALL adding prepare/execute/finalize for call main
+Calling convention __stackcall adding prepare/execute/finalize for call printline
+Calling convention __stackcall adding prepare/execute/finalize for call main
CONTROL FLOW GRAPH SSA
diff --git a/src/test/ref/procedure-callingconvention-stack-9.log b/src/test/ref/procedure-callingconvention-stack-9.log
index 6850418e0..d2b45c07f 100644
--- a/src/test/ref/procedure-callingconvention-stack-9.log
+++ b/src/test/ref/procedure-callingconvention-stack-9.log
@@ -1,11 +1,11 @@
Inlined call call __init
Converting PHI-variable modified inside __stackcall procedure main() to load/store val
-Calling convention STACK_CALL adding prepare/execute/finalize for call pval
-Calling convention STACK_CALL adding prepare/execute/finalize for call printother
-Calling convention STACK_CALL adding prepare/execute/finalize for call ival
-Calling convention STACK_CALL adding prepare/execute/finalize for call printval
-Calling convention STACK_CALL adding prepare/execute/finalize for call incval
-Calling convention STACK_CALL adding prepare/execute/finalize for call main
+Calling convention __stackcall adding prepare/execute/finalize for call pval
+Calling convention __stackcall adding prepare/execute/finalize for call printother
+Calling convention __stackcall adding prepare/execute/finalize for call ival
+Calling convention __stackcall adding prepare/execute/finalize for call printval
+Calling convention __stackcall adding prepare/execute/finalize for call incval
+Calling convention __stackcall adding prepare/execute/finalize for call main
CONTROL FLOW GRAPH SSA
diff --git a/src/test/ref/varcall-1.asm b/src/test/ref/varcall-1.asm
new file mode 100644
index 000000000..f1c39cf36
--- /dev/null
+++ b/src/test/ref/varcall-1.asm
@@ -0,0 +1,26 @@
+// Test __varcall calling convention
+.pc = $801 "Basic"
+:BasicUpstart(main)
+.pc = $80d "Program"
+ .label BGCOL = $d021
+// setbg(byte zp(2) col)
+setbg: {
+ .label col = 2
+ // *BGCOL = col
+ lda.z col
+ sta BGCOL
+ // }
+ rts
+}
+main: {
+ // setbg(0)
+ lda #0
+ sta.z setbg.col
+ jsr setbg
+ // setbg(0x0b)
+ lda #$b
+ sta.z setbg.col
+ jsr setbg
+ // }
+ rts
+}
diff --git a/src/test/ref/varcall-1.cfg b/src/test/ref/varcall-1.cfg
new file mode 100644
index 000000000..851070d5b
--- /dev/null
+++ b/src/test/ref/varcall-1.cfg
@@ -0,0 +1,19 @@
+
+__varcall void setbg(byte setbg::col)
+setbg: scope:[setbg] from
+ [0] *BGCOL = setbg::col
+ to:setbg::@return
+setbg::@return: scope:[setbg] from setbg
+ [1] return
+ to:@return
+
+void main()
+main: scope:[main] from
+ [2] setbg::col = 0
+ [3] callexecute setbg
+ [4] setbg::col = $b
+ [5] callexecute setbg
+ to:main::@return
+main::@return: scope:[main] from main
+ [6] return
+ to:@return
diff --git a/src/test/ref/varcall-1.log b/src/test/ref/varcall-1.log
new file mode 100644
index 000000000..3c9da72d6
--- /dev/null
+++ b/src/test/ref/varcall-1.log
@@ -0,0 +1,219 @@
+Calling convention __varcall adding prepare/execute/finalize for call setbg 0
+Calling convention __varcall adding prepare/execute/finalize for call setbg $b
+Converting parameter in __varcall procedure to load/store setbg::col
+
+CONTROL FLOW GRAPH SSA
+
+void main()
+main: scope:[main] from __start
+ setbg::col = 0
+ callexecute setbg
+ setbg::col = $b
+ callexecute setbg
+ to:main::@return
+main::@return: scope:[main] from main
+ return
+ to:@return
+
+__varcall void setbg(byte setbg::col)
+setbg: scope:[setbg] from
+ *BGCOL = setbg::col
+ to:setbg::@return
+setbg::@return: scope:[setbg] from setbg
+ return
+ to:@return
+
+void __start()
+__start: scope:[__start] from
+ call main
+ to:__start::@1
+__start::@1: scope:[__start] from __start
+ to:__start::@return
+__start::@return: scope:[__start] from __start::@1
+ return
+ to:@return
+
+SYMBOL TABLE SSA
+const nomodify byte* BGCOL = (byte*)$d021
+void __start()
+void main()
+__varcall void setbg(byte setbg::col)
+byte setbg::col loadstore
+
+Adding number conversion cast (unumber) 0 in setbg::col = 0
+Adding number conversion cast (unumber) $b in setbg::col = $b
+Successful SSA optimization PassNAddNumberTypeConversions
+Inlining cast setbg::col = (unumber)0
+Inlining cast setbg::col = (unumber)$b
+Successful SSA optimization Pass2InlineCast
+Simplifying constant pointer cast (byte*) 53281
+Simplifying constant integer cast 0
+Simplifying constant integer cast $b
+Successful SSA optimization PassNCastSimplification
+Finalized unsigned number type 0
+Finalized unsigned number type $b
+Successful SSA optimization PassNFinalizeNumberTypeConversions
+Removing unused procedure __start
+Removing unused procedure block __start
+Removing unused procedure block __start::@1
+Removing unused procedure block __start::@return
+Successful SSA optimization PassNEliminateEmptyStart
+CALL GRAPH
+Calls in [main] to setbg:3 setbg:5
+
+Created 0 initial phi equivalence classes
+Coalesced down to 0 phi equivalence classes
+
+FINAL CONTROL FLOW GRAPH
+
+__varcall void setbg(byte setbg::col)
+setbg: scope:[setbg] from
+ [0] *BGCOL = setbg::col
+ to:setbg::@return
+setbg::@return: scope:[setbg] from setbg
+ [1] return
+ to:@return
+
+void main()
+main: scope:[main] from
+ [2] setbg::col = 0
+ [3] callexecute setbg
+ [4] setbg::col = $b
+ [5] callexecute setbg
+ to:main::@return
+main::@return: scope:[main] from main
+ [6] return
+ to:@return
+
+
+VARIABLE REGISTER WEIGHTS
+void main()
+__varcall void setbg(byte setbg::col)
+byte setbg::col loadstore 7.5
+
+Initial phi equivalence classes
+Added variable setbg::col to live range equivalence class [ setbg::col ]
+Complete equivalence classes
+[ setbg::col ]
+Allocated zp[1]:2 [ setbg::col ]
+REGISTER UPLIFT POTENTIAL REGISTERS
+Statement [0] *BGCOL = setbg::col [ ] ( setbg:3 [ ] { } setbg:5 [ ] { } ) always clobbers reg byte a
+Statement [2] setbg::col = 0 [ setbg::col ] ( [ setbg::col ] { } ) always clobbers reg byte a
+Statement [4] setbg::col = $b [ setbg::col ] ( [ setbg::col ] { } ) always clobbers reg byte a
+Potential registers zp[1]:2 [ setbg::col ] : zp[1]:2 ,
+
+REGISTER UPLIFT SCOPES
+Uplift Scope [setbg] 7.5: zp[1]:2 [ setbg::col ]
+Uplift Scope [main]
+Uplift Scope []
+
+Uplifting [setbg] best 47 combination zp[1]:2 [ setbg::col ]
+Uplifting [main] best 47 combination
+Uplifting [] best 47 combination
+Attempting to uplift remaining variables inzp[1]:2 [ setbg::col ]
+Uplifting [setbg] best 47 combination zp[1]:2 [ setbg::col ]
+
+ASSEMBLER BEFORE OPTIMIZATION
+ // File Comments
+// Test __varcall calling convention
+ // Upstart
+.pc = $801 "Basic"
+:BasicUpstart(main)
+.pc = $80d "Program"
+ // Global Constants & labels
+ .label BGCOL = $d021
+ // setbg
+// setbg(byte zp(2) col)
+setbg: {
+ .label col = 2
+ // [0] *BGCOL = setbg::col -- _deref_pbuc1=vbuz1
+ lda.z col
+ sta BGCOL
+ jmp __breturn
+ // setbg::@return
+ __breturn:
+ // [1] return
+ rts
+}
+ // main
+main: {
+ // [2] setbg::col = 0 -- vbuz1=vbuc1
+ lda #0
+ sta.z setbg.col
+ // [3] callexecute setbg -- jsr
+ jsr setbg
+ // [4] setbg::col = $b -- vbuz1=vbuc1
+ lda #$b
+ sta.z setbg.col
+ // [5] callexecute setbg -- jsr
+ jsr setbg
+ jmp __breturn
+ // main::@return
+ __breturn:
+ // [6] return
+ rts
+}
+ // File Data
+
+ASSEMBLER OPTIMIZATIONS
+Removing instruction jmp __breturn
+Removing instruction jmp __breturn
+Succesful ASM optimization Pass5NextJumpElimination
+Removing instruction __breturn:
+Removing instruction __breturn:
+Succesful ASM optimization Pass5UnusedLabelElimination
+
+FINAL SYMBOL TABLE
+const nomodify byte* BGCOL = (byte*) 53281
+void main()
+__varcall void setbg(byte setbg::col)
+byte setbg::col loadstore zp[1]:2 7.5
+
+zp[1]:2 [ setbg::col ]
+
+
+FINAL ASSEMBLER
+Score: 41
+
+ // File Comments
+// Test __varcall calling convention
+ // Upstart
+.pc = $801 "Basic"
+:BasicUpstart(main)
+.pc = $80d "Program"
+ // Global Constants & labels
+ .label BGCOL = $d021
+ // setbg
+// setbg(byte zp(2) col)
+setbg: {
+ .label col = 2
+ // *BGCOL = col
+ // [0] *BGCOL = setbg::col -- _deref_pbuc1=vbuz1
+ lda.z col
+ sta BGCOL
+ // setbg::@return
+ // }
+ // [1] return
+ rts
+}
+ // main
+main: {
+ // setbg(0)
+ // [2] setbg::col = 0 -- vbuz1=vbuc1
+ lda #0
+ sta.z setbg.col
+ // [3] callexecute setbg -- jsr
+ jsr setbg
+ // setbg(0x0b)
+ // [4] setbg::col = $b -- vbuz1=vbuc1
+ lda #$b
+ sta.z setbg.col
+ // [5] callexecute setbg -- jsr
+ jsr setbg
+ // main::@return
+ // }
+ // [6] return
+ rts
+}
+ // File Data
+
diff --git a/src/test/ref/varcall-1.sym b/src/test/ref/varcall-1.sym
new file mode 100644
index 000000000..c7e1f8718
--- /dev/null
+++ b/src/test/ref/varcall-1.sym
@@ -0,0 +1,6 @@
+const nomodify byte* BGCOL = (byte*) 53281
+void main()
+__varcall void setbg(byte setbg::col)
+byte setbg::col loadstore zp[1]:2 7.5
+
+zp[1]:2 [ setbg::col ]