Optimize sign extension to AY

codeGenCpu6502/src/prog8/codegen/cpu6502/AsmGen.kt

@@ -1707,7 +1707,13 @@ $repeatLabel    lda  $counterVar
         // sign extend signed byte in A to full word in AY
         when(valueDt) {
             DataType.UBYTE -> out("  ldy  #0")
-            DataType.BYTE -> out("  jsr  prog8_lib.sign_extend_AY_byte")
+            DataType.BYTE -> out("""
+                ldy  #0
+                cmp  #$80
+                bcc  +
+                dey
++
+            """)
             else -> throw AssemblyError("need byte type")
         }
     }

compiler/res/prog8lib/prog8_lib.asm

@@ -1158,20 +1158,6 @@ sign_extend_stack_byte	.proc
 		rts
 		.pend
 
-
-sign_extend_AY_byte	.proc
-	; -- sign extend the (signed) byte in AY to full 16 bits
-		pha
-		and  #$80
-		beq  +
-		ldy  #$ff
-		pla
-		rts
-+		ldy  #0
-		pla
-		rts
-		.pend
-
 strlen          .proc
         ; -- returns the number of bytes in the string in AY, in Y.
 		sta  P8ZP_SCRATCH_W1