Add instruction for 'revb' - reverse bytes in a word.

Author: dpt

aha.h

@@ -4,7 +4,7 @@
 #include "simulator.h"
 
 #ifndef NARGS
-#define NARGS 1                 // Number of args in userfun, 1 or 2.
+#define NARGS 1                 // Number of args in userfun, 1, 2 or 3.
 #endif
 
 const int debug = 0;            // 0 or 1; debugging printouts if 1.

machine.h

@@ -33,6 +33,7 @@ static const isa_t isa[] = {
 // {seleq,  3, 0, {RX,  0,  0}, "seleq", "seleq(", ", " },  // Select if = 0.
 // {sellt,  3, 0, {RX,  0,  0}, "sellt", "sellt(", ", " },  // Select if < 0.
 // {selle,  3, 0, {RX,  0,  0}, "selle", "selle(", ", " },  // Select if <= 0.
+    {revb,   1, 0, {RX,   0, 0}, "revb",   "revb(",  ""     }, // Byte reversal.
 };
 
 #endif /* MACHINE_H */

simulator.c

@@ -43,6 +43,13 @@ int rev(int xi, int y, int z) {
    return x;
 }
 
+int revb(int xi, int y, int z) {
+   unsigned x = xi;
+   return ((x & 0x000000FF) << 24) | ((x >> 24) & 0x000000FF) |
+          ((x & 0x0000FF00) <<  8) | ((x >>  8) & 0x0000FF00);
+}
+
+
 int add (int x, int y, int z) {return x + y;}
 int sub (int x, int y, int z) {return x - y;}
 int rsb (int x, int y, int z) {return y - x;}

simulator.h

@@ -5,9 +5,9 @@
 
 typedef int (simproc)(int, int, int);
 
-simproc neg, _not, pop, nlz, rev, add, sub, rsb, mul, _div, _divu, _mod,
-        _modu, _and, _or, _xor, _bic, rotl, rotr, shl, shr, shrs, cmpeq,
-        cmplt, cmpltu, seleq, sellt, selle;
+simproc neg, _not, pop, nlz, rev, revb, add, sub, rsb, mul, _div, _divu,
+        _mod, _modu, _and, _or, _xor, _bic, rotl, rotr, shl, shr, shrs,
+        cmpeq, cmplt, cmpltu, seleq, sellt, selle;
 
 #endif /* SIMULATOR_H */