Add optimization to conditionals that always/never jump.

Author: dmsc

src/compiler/peephole.cc

@@ -1313,6 +1313,49 @@ class peephole
                         del(3);
                     }
                 }
+                //   x == 0 -> 1 / 0
+                if(mtok(0, "TOK_NUM") && mword(1) && mtok(2, "TOK_COMP_0"))
+                {
+                    set_w(1, val(1) ? 1 : 0);
+                    del(2);
+                    continue;
+                }
+                //   x / TOK_CNJUMP -> remove or always jump
+                if(mtok(0, "TOK_NUM") && mword(1) && mtok(2, "TOK_CNJUMP"))
+                {
+                    if(!val(1))
+                    {
+                        del(3);
+                        del(2);
+                        del(1);
+                        del(0);
+                    }
+                    else
+                    {
+                        set_tok(2, "TOK_JUMP");
+                        del(1);
+                        del(0);
+                    }
+                    continue;
+                }
+                //   x / TOK_CJUMP -> remove or always jump
+                if(mtok(0, "TOK_NUM") && mword(1) && mtok(2, "TOK_CJUMP"))
+                {
+                    if(val(1))
+                    {
+                        del(3);
+                        del(2);
+                        del(1);
+                        del(0);
+                    }
+                    else
+                    {
+                        set_tok(2, "TOK_JUMP");
+                        del(1);
+                        del(0);
+                    }
+                    continue;
+                }
                 // CALL xxxxx / RETURN  ->  JUMP xxxxx
                 //   TOK_CALL / x / TOK_RET -> TOK_JUMP / x
                 if(mtok(0, "TOK_CALL") && mtok(2, "TOK_RET"))

testsuite/tests/testloop.bas

@@ -98,3 +98,31 @@ for i=1 to 10
 next i
 ? "="; a
 
+' Check "void" loop optimizations
+repeat
+ ? "repeat until 1"
+until 1
+
+while 0
+ ? "while 0"
+wend
+
+' Check "always" loop optimizations
+i = 0
+repeat
+ ? "repeat until 0"
+ inc i
+ if i > 4 then exit
+until 0
+
+i = 0
+while 1
+ ? "while 1"
+ inc i
+ if i > 4 then exit
+wend
+
+' Check IF/FOR special
+if 0 then ? "if 0"
+if 1 then ? "if 1"
+for I=1 to 0 : ? "for 0" : next

testsuite/tests/testloop.chk

@@ -51,3 +51,15 @@ Test nested FOR with EXIT
 9         10        =2
 10        =3
 =295
+repeat until 1
+repeat until 0
+repeat until 0
+repeat until 0
+repeat until 0
+repeat until 0
+while 1
+while 1
+while 1
+while 1
+while 1
+if 1