added read_flags() function, uword2bcd routine no longer enables irq again if it wasn't enabled before calling it.

compiler/res/prog8lib/c64utils.p8

@@ -99,6 +99,10 @@ asmsub  uword2bcd  (uword value @ AY) -> clobbers(A,Y) -> ()  {
 	%asm {{
 		sta  c64.SCRATCH_ZPB1
 		sty  c64.SCRATCH_ZPREG
+		php
+		pla             ; read status register
+		and  #%00000100
+		sta  _had_irqd
 		sei				; disable interrupts because of bcd math
 		sed				; switch to decimal mode
 		lda  #0				; ensure the result is clear
@@ -121,8 +125,11 @@ asmsub  uword2bcd  (uword value @ AY) -> clobbers(A,Y) -> ()  {
 		dey				; and repeat for next bit
 		bne  -
 		cld				; back to binary
-		cli				; enable interrupts again      @todo don't re-enable if it wasn't enabled before
-		rts
+		lda  _had_irqd
+		bne  +
+		cli				; enable interrupts again (only if they were enabled before)
++		rts
+_had_irqd  .byte  0
 	}}
 }
 
@@ -987,7 +994,7 @@ asmsub  getchr  (ubyte col @Y, ubyte row @A) -> clobbers(Y) -> (ubyte @ A) {
 		bcc  _mod
 		inc  _mod+2
 _mod		lda  $ffff		; modified
-		rts		
+		rts
 	}}
 }
 
@@ -1028,7 +1035,7 @@ asmsub  getclr  (ubyte col @Y, ubyte row @A) -> clobbers(Y) -> (ubyte @ A) {
 		bcc  _mod
 		inc  _mod+2
 _mod		lda  $ffff		; modified
-		rts		
+		rts
 	}}
 }
 

compiler/res/prog8lib/prog8lib.asm

@@ -640,6 +640,15 @@ greatereq_w	.proc
 		bmi  equal_b._equal_b_false
 		.pend
 
+func_read_flags	.proc
+		; -- put the processor status register on the stack
+		php
+		pla
+		sta  c64.ESTACK_LO,x
+		dex
+		rts
+		.pend
+		
 
 func_sin8	.proc
 		ldy  c64.ESTACK_LO+1,x

compiler/src/prog8/functions/BuiltinFunctions.kt

@@ -70,6 +70,7 @@ val BuiltinFunctions = mapOf(
     "clear_carry" to FunctionSignature(false, emptyList(), null),
     "set_irqd"    to FunctionSignature(false, emptyList(), null),
     "clear_irqd"  to FunctionSignature(false, emptyList(), null),
+    "read_flags"  to FunctionSignature(false, emptyList(), DataType.UBYTE),
     "swap"        to FunctionSignature(false, listOf(BuiltinFunctionParam("first", NumericDatatypes), BuiltinFunctionParam("second", NumericDatatypes)), null),
     "memcopy"     to FunctionSignature(false, listOf(
                                                         BuiltinFunctionParam("from", IterableDatatypes + setOf(DataType.UWORD)),

compiler/src/prog8/stackvm/StackVm.kt

@@ -80,7 +80,8 @@ enum class Syscall(val callNr: Short) {
     FUNC_SUM_F(134),
     FUNC_MEMCOPY(138),
     FUNC_MEMSET(139),
-    FUNC_MEMSETW(140)
+    FUNC_MEMSETW(140),
+    FUNC_READ_FLAGS(141)
 
     // note: not all builtin functions of the Prog8 language are present as functions:
     // some of them are straight opcodes (such as MSB, LSB, LSL, LSR, ROL_BYTE, ROR, ROL2, ROR2, and FLT)!
@@ -1613,6 +1614,14 @@ class StackVm(private var traceOutputFile: String?) {
                 val text = heap.get(strPtr).str!!
                 evalstack.push(Value(DataType.UBYTE, text.length))
             }
+            Syscall.FUNC_READ_FLAGS -> {
+                val carry = if(P_carry) 1 else 0
+                val zero = if(P_zero) 2 else 0
+                val irqd = if(P_irqd) 4 else 0
+                val negative = if(P_negative) 128 else 0
+                val flags = carry or zero or irqd or negative
+                evalstack.push(Value(DataType.UBYTE, flags))
+            }
             Syscall.FUNC_SIN -> evalstack.push(Value(DataType.FLOAT, sin(evalstack.pop().numericValue().toDouble())))
             Syscall.FUNC_COS -> evalstack.push(Value(DataType.FLOAT, cos(evalstack.pop().numericValue().toDouble())))
             Syscall.FUNC_SIN8 -> {

docs/source/programming.rst

@@ -735,3 +735,6 @@ rsave()
 
 rrestore()
     Restores the CPU registers and the status flags from previously saved values.
+
+read_flags()
+    Returns the current value of the CPU status register.

docs/source/targetsystem.rst

@@ -117,7 +117,8 @@ The following 6502 CPU hardware registers are directly usable in program code (a
 
 - ``A``, ``X``, ``Y``  the three main cpu registers (8 bits)
 - the status register (P) carry flag and interrupt disable flag can be written via a couple of special
-  builtin functions (``set_carry()``, ``clear_carry()``, ``set_irqd()``,  ``clear_irqd()``)
+  builtin functions (``set_carry()``, ``clear_carry()``, ``set_irqd()``,  ``clear_irqd()``),
+  and read via the ``read_flags()`` function.
 
 However, you must assume that the 3 hardware registers ``A``, ``X`` and ``Y``
 are volatile. Their values cannot be depended upon, the compiler will use them as required.

examples/test.p8

@@ -9,11 +9,34 @@
 
     sub start() {
 
-    for ubyte @zp fastindex in 10 to 20 {
-        c64scr.print_ub(fastindex)
+        uword w = 12345
+        ubyte flags
+
+        c64.CHROUT('\n')
+
+        clear_irqd()
+        c64utils.uword2bcd(w)
+        flags=read_flags()
+        c64scr.print_ubbin(1,flags)
+        c64.CHROUT('\n')
+
+        set_irqd()
+        c64utils.uword2bcd(w)
+        flags=read_flags()
+        c64scr.print_ubbin(1,flags)
+        c64.CHROUT('\n')
+
+        clear_irqd()
+        c64utils.uword2bcd(w)
+        flags=read_flags()
+        c64scr.print_ubbin(1,flags)
+        c64.CHROUT('\n')
+
+        set_irqd()
+        c64utils.uword2bcd(w)
+        flags=read_flags()
+        c64scr.print_ubbin(1,flags)
         c64.CHROUT('\n')
-        ; do something
-    }
 
     }
 }