fix forloop 6502 codegen in case of descending word values

codeGenIntermediate/src/prog8/codegen/intermediate/IRCodeGen.kt

@@ -552,16 +552,16 @@ class IRCodeGen(
 
         addInstr(result, IRInstruction(Opcode.STOREM, loopvarDtIr, reg1=fromTr.resultReg, labelSymbol=loopvarSymbol), null)
         result += labelFirstChunk(translateNode(forLoop.statements), loopLabel)
-        addInstr(result, IRInstruction(Opcode.LOADM, loopvarDtIr, reg1 = fromTr.resultReg, labelSymbol = loopvarSymbol), null)
         if(step==1 || step==-1) {
-            // if endvalue == index, stop loop, else iterate
+            // if endvalue == loopvar, stop loop, else iterate
+            addInstr(result, IRInstruction(Opcode.LOADM, loopvarDtIr, reg1 = fromTr.resultReg, labelSymbol = loopvarSymbol), null)
             addInstr(result, IRInstruction(Opcode.BEQR, loopvarDtIr, reg1=toTr.resultReg, reg2=fromTr.resultReg, labelSymbol = labelAfterFor), null)
             result += addConstMem(loopvarDtIr, null, loopvarSymbol, step)
             addInstr(result, IRInstruction(Opcode.JUMP, labelSymbol = loopLabel), null)
         } else {
             // ind/dec index, then:
-            // ascending: if endvalue >= index, iterate
+            // ascending: if endvalue >= loopvar, iterate
-            // descending: if index >= endvalue, iterate
+            // descending: if loopvar >= endvalue, iterate
             result += addConstMem(loopvarDtIr, null, loopvarSymbol, step)
             addInstr(result, IRInstruction(Opcode.LOADM, loopvarDtIr, reg1=fromTr.resultReg, labelSymbol = loopvarSymbol), null)
             if(step > 0)

docs/source/todo.rst

@@ -1,11 +1,7 @@
 TODO
 ====
 
-- investigate if the hiscores issue on the forum is a compiler bug or not.
-
 - IR: instructions that do type conversion (SZ etc, CONCAT, SGN) should put the result in a DIFFERENT register.
-- IR: optimize forloop codegen to use a reg as loop variable instead of a memory variable, just store it in the mem var before entering the loop body
-      check repeat loop as well it shouldn't be using a tempvar just a register to count.
 
 ...
 

examples/test.p8

@@ -1,56 +1,32 @@
-%import string
 %import textio
-%import conv
-
 %zeropage basicsafe
 
+; (127 instructions in 15 chunks, 47 registers)
+; 679 steps
+
+
 main {
 
-str[10] names = ["1??","2??","3??","4??","5??","6??","7??","8??","9??","a??"]
-str[10] scores = ["9000","8000","7000","6000","5000","4000","3000","2000","1000","50"]
-str p_str = "winner"
-uword top_score
-
 sub start() {
-    print_hiscores()
+    uword i
-    ubyte r = check_score(7500)
+    uword n
-    print_hiscores()
-}
 
-sub check_score(uword score) -> ubyte {
+    repeat 10 {
-	ubyte n
+        txt.chrout('.')
-	ubyte i
+    }
-	str tmp = "?????"
+    txt.nl()
     
-	if score < top_score {
+    n=10
-		return(10) }
+    for i in 0 to n step 3 {
-	else {
+        txt.print_uw(i)
-		for n in 0 to 9 {
-			if score > conv.str2uword(scores[n]) {
-				for i in 8 to n step -1 {
-					names[i+1] = names[i]
-					scores[i+1] = scores[i]
-			    }
-				;string.copy(p_str,names[n])
-				;conv.str_uw0(score)
-				;string.copy(conv.string_out,scores[n])
-				return(n)
-			}
-		}
-	}
-}
-
-sub print_hiscores() {
-	ubyte n
-	for n in 0 to 9 {
-		txt.print_ub(n)
-		txt.spc()
-		txt.print(names[n])
-		txt.spc()
-		txt.print(scores[n])
         txt.nl()
     }
     txt.nl()
-}
 
+    n=0
+    for i in 10 downto n step -3 {
+        txt.print_uw(i)
+        txt.nl()
+    }
+}
 }