new version

NOTE: `t` and `x` registers swapped, otherwise we would overwrite Xlo

diff --git a/foo.c b/foo.c
index 1bc2f04..29ddee4 100644 (file)
--- a/foo.c
+++ b/foo.c
@@ -2,10 +2,6 @@
 #include "fakeasm.h"
 typedef unsigned char u8;
 
-u8 data[] = {   
-       0x84, 0x9d, 0xb0, 0x69, 0x9d, 0x84, 0x69, 0x58,
-       0x75, 0x8c, 0xb0, 0x69, 0x8c, 0x75, 0x69, 0x58
-};
 u8 zero;       //r16
 u8 acc;                //r17
 u8 i0;         //r18
@@ -16,12 +12,12 @@ u8 n;               //r22
 u8 s;          //r23
 u8 _;          //r24
                //r25
-u8 t;/*==Ml*/  //r26 (Xlo)
-u8 x;/*==Mh*/  //r27 (Xhi)
+u8 x;/*==Ml*/  //r26 (Xlo)
+u8 t;/*==Mh*/  //r27 (Xhi)
                //r28
                //r29
-/*fakestack_l*/        //r30 (Zlo)
-/*fakestack_h*/        //r31 (Zhi)
+void *Z;       //r30 (Zlo)
+/*...*/                //r31 (Zhi)
 #define Mh x //mod3 vars
 #define Ml t // -"-
 //http://homepage.divms.uiowa.edu/~jones/bcd/mod.shtml
@@ -58,6 +54,11 @@ void mod3(void) {
 void g(void) {
        // g(i, t) -> t
        // tempvars: `x` and `_`
+static void* mul_jmptable[] = { // replaces data[] section at the top
+       &&mul_84, &&mul_9d, &&mul_b0, &&mul_69, &&mul_9d, &&mul_84, &&mul_69, &&mul_58,
+       &&mul_75, &&mul_8c, &&mul_b0, &&mul_69, &&mul_8c, &&mul_75, &&mul_69, &&mul_58
+       // addresses of mul_* stored in little endian (i.e. { lo(mul_84), hi(mul_84), ... })
+};
        #define tmp _
        ANDI    (t, 0x07)
        MOV     (tmp, i2)
@@ -66,62 +67,25 @@ void g(void) {
        #undef tmp
        BREQ    (skip)
        SUBI    (t, -8)
-       skip:
-       //TODO: directly load address to mul_* routine and jump to it?
-       ;static void* mul_jmptable[] = {   
-               &&mul_84, &&mul_9d, &&mul_b0, &&mul_69, &&mul_9d, &&mul_84, &&mul_69, &&mul_58,
-               &&mul_75, &&mul_8c, &&mul_b0, &&mul_69, &&mul_8c, &&mul_75, &&mul_69, &&mul_58
-       };
-       void *t_;
-       t_ = mul_jmptable[t];
+       skip:;
        #define a1 x
        #define a2 _
        #define a0 t
        CLR     (a2)
        CLR     (a1)
-       goto *t_; //GNU extension simulates indirect jump
-       /*
-         LDI  Xlo==x, data_lo
+       goto *mul_jmptable[t]; /*
+         LDI  Xlo, lo(mul_jmptable)
+         LDI  Xhi, hi(mul_jmptable)
          ADD  Xlo, t
-         ADD  Xlo, t  ; 16 bit value; advance by 2*u8
-         LDI  Xhi==t, data_hi <--this won't work, need t afterwards
+         ADC  Xhi, zero
+         ADD  Xlo, t      ; advance twice, since it's a 16 bit address
          ADC  Xhi, zero
          LD   Zlo, X
          SUBI Xlo, -1
          ADC  Xhi, zero
          LD   Zhi, X
-         IJMP Z
-       */
-#if 0
-       t = data[t];
-       /*MOV X_hi==x, data_hi _
-         MOV X_lo==t, data_lo  \_ this won't
-         ADD X_lo, t          _/  work! XXX
-         ADC X_hi, zero
-         LD  t, X         */
-       #define a1 x
-       #define a2 _
-       #define a0 t
-       // start MUL
-       CLR     (a2)
-       CLR     (a1)
-#endif
+         IJMP Z */
 
-       //sorted by ocurrence, then longest cycle count first
-       CPI     (t, 0x69)
-       BREQ    (mul_69)
-       CPI     (t, 0x75)
-       BREQ    (mul_75)
-       CPI     (t, 0x9d)
-       BREQ    (mul_9d)
-       CPI     (t, 0x58)
-       BREQ    (mul_58)
-       CPI     (t, 0x8c)
-       BREQ    (mul_8c)
-       CPI     (t, 0x84)
-       BREQ    (mul_84)
-       CPI     (t, 0xb0)
-       BREQ    (mul_b0)
        mul_58: // 0101 1000 (24cy)
                LSR (a2)
                ROR (a1)