added math.mul16_last_upper() to fetch the upper 16 bits of the last word multiplication

compiler/res/prog8lib/math.p8

@@ -140,6 +140,16 @@ _sinecosR8	.char  trunc(127.0 * sin(range(180+45) * rad(360.0/180.0)))
         }}
     }
 
+    asmsub mul16_last_upper() -> uword @AY {
+        ; this routine peeks into the internal 32 bits multiplication result buffer of the
+        ; 16*16 bits multiplication routine, to fetch the upper 16 bits of the last calculation.
+        %asm {{
+            lda  multiply_words.result+2
+            ldy  multiply_words.result+3
+            rts
+        }}
+    }
+
 sub direction_sc(byte x1, byte y1, byte x2, byte y2) -> ubyte {
     ; From a pair of signed coordinates around the origin, calculate discrete direction between 0 and 23 into A.
     cx16.r0L = 3        ; quadrant

compiler/res/prog8lib/virtual/math.p8

@@ -2,6 +2,9 @@
 
 math {
 
+    ; TODO: the VM doesn't yet store the full 32 bits result of a 16*16 multiplication, so there is NO mul16_last_upper() routine here at this time.
+
+
     sub sin8u(ubyte angle) -> ubyte {
         ubyte[256] sintab = [$80, $83, $86, $89, $8c, $8f, $92, $95, $98, $9b, $9e, $a2, $a5, $a7, $aa, $ad, $b0, $b3, $b6, $b9,
                              $bc, $be, $c1, $c4, $c6, $c9, $cb, $ce, $d0, $d3, $d5, $d7, $da, $dc, $de, $e0,

docs/source/todo.rst

@@ -1,6 +1,10 @@
 TODO
 ====
 
+- VM: make matn.mul16_last_upper()
+- clean up the active file channel assumptions in diskio (basically do chkin every time and not in f_open?)
+- return the file channel number from f_open and f_open_w instead of just true (so user can change it and set it back if they want instead of relying on the magic numbers 12 and 13)
+  OR just add routines to set it back to 12/13 so no tracking has to occur by the user at all
 - add a compiler switch to replace all calls to the math word mul routine on the X16 by the verafx call instead.
 - [on branch: shortcircuit] investigate McCarthy evaluation again? this may also reduce code size perhaps for things like if a>4 or a<2 ....
 - [on branch: ir-less-branch-opcodes] IR: reduce the number of branch instructions such as BEQ, BEQR, etc (gradually), replace with CMP(I) + status branch instruction

examples/test.p8

@@ -1,38 +1,50 @@
 %import textio
-%import verafx
+;%import verafx
 %zeropage basicsafe
 %option no_sysinit
 
 main {
     sub start() {
 
-        const word MULTIPLIER = 431
 
-        ; verify results:
-        for value in -50 to 50 {
-            if value*MULTIPLIER != verafx.muls(value, MULTIPLIER) {
-                txt.print("verafx muls error\n")
-                sys.exit(1)
-            }
-        }
-
-
-        word value
-        txt.print("verafx muls...")
-        cbm.SETTIM(0,0,0)
-        for value in -50 to 50 {
-            repeat 250 void verafx.muls(value, MULTIPLIER)
-        }
-        txt.print_uw(cbm.RDTIM16())
+        txt.print_uw(math.mul16_last_upper())
+        txt.nl()
+        uword value1=5678
+        uword value2=9999
+        uword result = value1*value2
+        txt.print_uw(result)
+        txt.spc()
+        txt.print_uw(math.mul16_last_upper())
         txt.nl()
 
-        txt.print("6502 muls...")
-        cbm.SETTIM(0,0,0)
-        for value in -50 to 50 {
-            repeat 250 cx16.r0s = value*MULTIPLIER
-        }
-        txt.print_uw(cbm.RDTIM16())
-        txt.nl()
+
+;        const word MULTIPLIER = 431
+;
+;        ; verify results:
+;        for value in -50 to 50 {
+;            if value*MULTIPLIER != verafx.muls(value, MULTIPLIER) {
+;                txt.print("verafx muls error\n")
+;                sys.exit(1)
+;            }
+;        }
+;
+;
+;        word value
+;        txt.print("verafx muls...")
+;        cbm.SETTIM(0,0,0)
+;        for value in -50 to 50 {
+;            repeat 250 void verafx.muls(value, MULTIPLIER)
+;        }
+;        txt.print_uw(cbm.RDTIM16())
+;        txt.nl()
+;
+;        txt.print("6502 muls...")
+;        cbm.SETTIM(0,0,0)
+;        for value in -50 to 50 {
+;            repeat 250 cx16.r0s = value*MULTIPLIER
+;        }
+;        txt.print_uw(cbm.RDTIM16())
+;        txt.nl()
 
     }
 }