Two mechanical fixes SplitLint found: MVQA, and RSTA for zero

Twenty four places moved Q into A or B by pushing it and popping it back.
That is four bus cycles and two bytes to do what MVQA does in one of each,
and several of them are inside loops - Life, the calculator, int8. Nineteen
more loaded zero with INIA 0d0 where RSTA says the same thing in one byte.

Both are equivalent at the CPU rather than by assertion: RSTA and INIA both
leave Status alone, and PSHQ followed by POPA nets to A = Q with the Stack
Pointer where it started. The one difference is that the pair leaves a copy
of Q in memory just below the Stack Pointer and MVQA does not, which
nothing here reads.

Five recorded outputs moved and every one of them says the change worked:

- 16x16Life fits five more generations into the same cycle budget, the
  first 457 lines identical, because the loop got cheaper.
- Life.sbx is 1409 bytes rather than 1411, in three tests that list it.
- Edit.sbx is 1995 rather than 1996.

That last one broke a check I added this morning, and the hole is worth
recording: the CosmOS README's claim about Edit's size did not have the
word "Edit" on the same line as the number, because the subject was in the
sentence before, so the check that measures quoted sizes skipped it
silently. The sentence now names what it is talking about, which makes it
both checkable and clearer, and the check fails on a wrong number there.

Comments on either half of a replaced pair are carried onto the
instruction that replaces them, so nothing anybody wrote was lost.

Programs/CosmOS/Apps/Fib-8.asm

@@ -8,7 +8,7 @@
 
 start:
   ; Load our initial values into A and B.
-  INIA 0x00
+  RSTA
   CALL printByteDecimal
   CALL blankSpace
   ; Move the value into B.
@@ -25,8 +25,7 @@ start:
   PSHA
   POPB
   ; Copy Q into A
-  PSHQ
-  POPA
+  MVQA
   ; Print A.
   CALL printByteDecimal
   CALL blankSpace

Programs/CosmOS/Assembler/classify.asm

@@ -33,7 +33,7 @@ clsToken:
   INIB 0x23                 ; '#'
   XOR
   BNQ clsTryInstruction
-  INIA 0d0
+  RSTA
   SETD.0 ClsType
   STA.0
   BRI clsYes

Programs/CosmOS/README.md

@@ -462,7 +462,7 @@ Typed in as bytes, checked by disassembling it back, and run. It ends with `SWI
 
 `Edit` is the first program on this machine that makes a file a person typed - every byte on every disk before it was put there by the host tool. It is line oriented in the manner of `ed`: `l` lists, `a` adds at the end, `i` and `c` and `d` take a line number, `w` writes and `q` stops.
 
-It includes nothing but `services.asm` and `text.asm`: the filesystem and the console are the system's, asked for rather than carried. That is what took it from 4,941 bytes to 1,996 without a line of its own logic changing - and the way that was checked is worth knowing, because the recorded output of the `cosmosEdit` test did not move by a single byte across the rewrite.
+It includes nothing but `services.asm` and `text.asm`: the filesystem and the console are the system's, asked for rather than carried. That is what brought `Edit` down from 4,941 bytes to 1,995 bytes without a line of its own logic changing - and the way that was checked is worth knowing, because the recorded output of the `cosmosEdit` test did not move by a single byte across the rewrite.
 
 It keeps the document as a **linked list of lines** rather than one buffer with newlines in it. Each line says where the next one is, how long it is, and then its bytes. Inserting is two pointers changed and nothing moved; with a flat buffer it would mean shifting every byte after the edit, on a machine whose only block move is a device asked politely. The price is that deleted lines are not reused, so a heavy session uses more room than the document needs and writing it out is what tidies up.
 

Programs/CosmOS/Source/text.asm

@@ -94,8 +94,7 @@ textHexWord:
 textHexLoop:
   LDA.0
   CALL textHexDigit
-  PSHQ
-  POPA
+  MVQA
   INIB 0xFF
   CCF
   SUB

Programs/Examples/Fibonacci/8bitFibonacci.asm

@@ -5,7 +5,7 @@
 #Program
 start:
   ; Load our initial values into A and B.
-  INIA 0x00
+  RSTA
   CALL printByteDecimal
   CALL blankSpace
   ; Move the value into B.
@@ -22,8 +22,7 @@ start:
   PSHA
   POPB
   ; Copy Q into A
-  PSHQ
-  POPA
+  MVQA
   ; Print A.
   CALL printByteDecimal
   CALL blankSpace

Programs/Examples/gameOfLife/16x16Life.asm

@@ -193,50 +193,43 @@ countNeighbors:
   LDB
   CCF
   ADD
-  PSHQ
-  POPA
+  MVQA
   DPUP 0d02
 
   LDB
   CCF
   ADD
-  PSHQ
-  POPA
+  MVQA
   DPUP 0d02
 
   LDB
   CCF
   ADD
-  PSHQ
-  POPA
+  MVQA
   DPUP 0d32
 
   LDB
   CCF
   ADD
-  PSHQ
-  POPA
+  MVQA
   DPUP 0d04
 
   LDB
   CCF
   ADD
-  PSHQ
-  POPA
+  MVQA
   DPUP 0d32
 
   LDB
   CCF
   ADD
-  PSHQ
-  POPA
+  MVQA
   DPUP 0d02
 
   LDB
   CCF
   ADD
-  PSHQ
-  POPA
+  MVQA
   DPUP 0d02
 
   LDB

Programs/Examples/inputTest.asm

@@ -20,7 +20,7 @@ start:
   INCD              ; Increment to the next spot in the buffer.
   BRI inputLoop     ; Loop again to grab more string.
  inputEnd:
-  INIA 0x00         ; Set A to 0.
+  RSTA         ; Set A to 0.
   STA               ; Store it in the buffer.
   SETD Buffer       ; Set the Data Pointer to the start of the buffer again.
   CALL printString  ; Print it out.

Programs/Examples/replCalculator.asm

@@ -18,8 +18,7 @@ repl:
   CALL printString
 
   CALL readNonSpace
-  PSHQ
-  POPA
+  MVQA
 
   ; Q, q, or end-of-file exits.
   INIB 0xFF
@@ -39,14 +38,12 @@ repl:
   BRQ inputError
 
   CALL readNonSpace
-  PSHQ
-  POPA
+  MVQA
   SETD Operator
   STA
 
   CALL readNonSpace
-  PSHQ
-  POPA
+  MVQA
   CALL readHexByteFirst
   SETD RightOperand
   STQ
@@ -98,7 +95,7 @@ readNonSpaceLoop:
   INIB 0x0D
   XOR
   BRQ readNonSpaceLoop
-  INIB 0x00
+  RSTB
   CCF
   ADD
   RET
@@ -108,12 +105,11 @@ readNonSpaceLoop:
 readHexByteFirst:
   CALL clearParseStatus
   CALL hexNibble
-  PSHQ
-  POPA
+  MVQA
   INIB 0xFF
   XOR
   BRQ invalidByte
-  INIB 0x00
+  RSTB
   SHL
   SHL
   SHL
@@ -121,11 +117,9 @@ readHexByteFirst:
   PSHA
 
   CALL readNonSpace
-  PSHQ
-  POPA
+  MVQA
   CALL hexNibble
-  PSHQ
-  POPA
+  MVQA
   INIB 0xFF
   XOR
   BRQ invalidLowNibble
@@ -142,7 +136,7 @@ invalidByte:
   STA
   POPD
   INIA 0xFF
-  INIB 0x00
+  RSTB
   CCF
   ADD
   RET
@@ -157,8 +151,7 @@ hexNibble:
   CCF
   SUB
   BRC tryUpperHex
-  PSHQ
-  POPA
+  MVQA
   INIB 0d10
   CCF
   SUB
@@ -171,8 +164,7 @@ tryUpperHex:
   CCF
   SUB
   BRC tryLowerHex
-  PSHQ
-  POPA
+  MVQA
   INIB 0d06
   CCF
   SUB
@@ -185,8 +177,7 @@ tryLowerHex:
   CCF
   SUB
   BRC badNibble
-  PSHQ
-  POPA
+  MVQA
   INIB 0d06
   CCF
   SUB
@@ -195,14 +186,14 @@ tryLowerHex:
 badNibble:
   POPA
   INIA 0xFF
-  INIB 0x00
+  RSTB
   CCF
   ADD
   RET
 
 decimalNibble:
   POPB
-  INIB 0x00
+  RSTB
   CCF
   ADD
   RET
@@ -223,8 +214,7 @@ lowerNibble:
 
 ; Return Q=0 if Q was 0xFF, otherwise return a nonzero value.
 resultIsInvalid:
-  PSHQ
-  POPA
+  MVQA
   INIB 0xFF
   XOR
   RET
@@ -288,7 +278,7 @@ evaluate:
   INIA 0x01
   STA
   RSTA
-  INIB 0x00
+  RSTB
   CCF
   ADD
   RET
@@ -360,7 +350,7 @@ multiplyLoop:
 multiplyDone:
   SETD Product
   LDA
-  INIB 0x00
+  RSTB
   CCF
   ADD
   RET

Programs/Libraries/int8.asm

@@ -25,8 +25,7 @@ int8mult:
   DECA ; Subtract one from the multiplier.
   BRA int8multDone ; If the multiplier becomes zero, we're done.
   PSHA ; Push the multiplier back to the stack.
-  PSHQ ; Push the running total to the stack.
-  POPA ; Pop the running total into A.
+  MVQA                 ; Push the running total to the stack. Pop the running total into A.
   BRI int8multLoop
  return0:
   RSTA
@@ -58,8 +57,7 @@ int8div:
   POPA ; Pop the quotient counter from the stack.
   INCA ; Increment it.
   PSHA ; Push it back onto the stack.
-  PSHQ ; Push the running total onto the stack.
-  POPA ; Pop the runing total into A.
+  MVQA                 ; Push the running total onto the stack. Pop the runing total into A.
   BRI int8divLoop ; Branch back to the loop.
  int8divDone:
   CCF  ; Clear the Carry Flag.
@@ -76,13 +74,11 @@ int8mod:
  int8modLoop:
   SUB ; Subtract B from A.
   BRC int8modDone
-  PSHQ
-  POPA
+  MVQA
   BRI int8modLoop
  int8modDone:
   ; Add the divisor to Q to get the remainder.
   CCF
-  PSHQ
-  POPA
+  MVQA
   ADD
   RET

Programs/Libraries/print.asm

@@ -97,10 +97,10 @@ printByteDecimal:
 
 ; Expects A to contain the byte you want to print as a hexadecimal value.
 printByteHex:
-  INIB 0x00                 ; Set B to 0.
+  RSTB                 ; Set B to 0.
   SHR SHR SHR SHR           ; Shift Right four times to move the high nybble into the lower half of A.
   CALL printHexDigit        ; Print the nybble.
-  INIA 0x00                 ; Set A to 0.
+  RSTA                 ; Set A to 0.
   SHL SHL SHL SHL           ; Shift left four times to move the low nybble back into the lower half of A.
   CALL printHexDigit        ; Print the nybble.
   RET                       ; Return to the caller.

Programs/testPrograms/inputTest.asm

@@ -20,7 +20,7 @@ start:
   INCD              ; Increment to the next spot in the buffer.
   BRI inputLoop     ; Loop again to grab more string.
  inputEnd:
-  INIA 0x00         ; Set A to 0.
+  RSTA         ; Set A to 0.
   STA               ; Store it in the buffer.
   SETD Buffer       ; Set the Data Pointer to the start of the buffer again.
   CALL printString  ; Print it out.

Programs/testPrograms/printTest.asm

@@ -8,8 +8,8 @@
 #Program
 
 clearRegisters:
-  INIA 0x00;
-  INIB 0x00;
+  RSTA
+  RSTB
   ADD
   RET
 

Programs/testPrograms/rawCallAndOffsets.asm

@@ -36,12 +36,12 @@ start:
 
   ; ---- Offsetting by a whole sixteen bit value ----
   SETD.1 Text
-  INIA 0x00
+  RSTA
   INIB 0d13
   DPUW.1
   LDA.1
   OUTA 0x00
-  INIA 0x00
+  RSTA
   INIB 0d13
   DPDW.1
   LDA.1

Programs/testPrograms/registryTest.asm

@@ -21,7 +21,7 @@
 #Program
 
 start:
-  INIA 0x00
+  RSTA
   CALL reportPort
   INIA 0x10
   CALL reportPort