added first CPU specific optimizations

c64/kernal/interrupts/ea81.return_from_interrupt.s

@@ -11,10 +11,16 @@ return_from_interrupt:
 
 	// Restore registers and return
 	// Sequence according to Compute's Mapping the 64 p73
+
+#if CONFIG_CPU_MOS_6502
 	pla
 	tay
 	pla
 	tax
+#else
+	ply
+	plx
+#endif
 	pla
 	rti
 

c64/kernal/interrupts/fe47.default_nmi_handler.s

@@ -6,10 +6,15 @@ default_nmi_handler:
 
 	// Save registers, sequence according to Compute's Mapping the Commodore 64, page 73
 	pha
+#if CONFIG_CPU_MOS_6502
 	txa
 	pha
 	tya
 	pha
+#else
+	phx
+	phy
+#endif
 
 	// XXX: RS-232 support is not implemented
 

c64/kernal/interrupts/irq_handler.s

@@ -10,12 +10,19 @@ irq_handler:
 
 	// Save registers, sequence according to Compute's Mapping the Commodore 64, page 73
 	pha
+#if CONFIG_CPU_MOS_6502
 	txa
 	pha
 	tya
 	pha
+#else
+	phx
+	phy
+#endif
 
-	cld // clear decimal flag, to prevent possible problems
+#if CONFIG_CPU_MOS_6502 && CONFIG_BCD_SAFE_INTERRUPTS
+	cld // clear decimal flag to allow using it without disabling interrupts
+#endif
 
 	// Check if caused by BRK
 	tsx

c64/kernal/interrupts/nmi_handler.s

@@ -2,7 +2,10 @@
 nmi_handler:
 
 	sei // don't allow IRQ to interfere, see https://www.c64-wiki.com/wiki/Interrupt
-	cld // clear decimal flag, to prevent possible problems
+
+#if CONFIG_CPU_MOS_6502 && CONFIG_BCD_SAFE_INTERRUPTS
+	cld // clear decimal flag to allow using it without disabling interrupts
+#endif
 
 	// Call interrupt routine (only if initialised)
 	pha

c64/kernal/printf.s

@@ -139,7 +139,13 @@ printf_retreat:
 	rts
 
 printf_printhexbyte:
-	// Print the hex value in .A as two digits, idea by Haubitze
+
+	// Print the hex value in .A as two digits
+
+#if HAS_BCD_SAFE_INTERRUPTS
+
+	// Idea by Haubitze
+
 	sed
 	pha
 	lsr
@@ -155,3 +161,25 @@ printf_printhexbyte:
 	adc #$30
 	cld
 	jmp JCHROUT
+
+#else
+
+	pha
+	lsr
+	lsr
+	lsr
+	lsr
+	ora #$30
+	cmp #$3A
+	bcc !+
+	adc #6
+!:	jsr JCHROUT
+	pla
+	and #$0f
+	ora #$30
+	cmp #$3A
+	bcc !+
+	adc #6
+!:	jmp JCHROUT
+
+#endif

c64/kernal/reset_entry.s

@@ -5,9 +5,10 @@
 reset_entry:
 
 	// The GPL program at https://github.com/Klaus2m5/6502_65C02_functional_tests/blob/master/6502_functional_test.a65
-	// uses the following initial reset sequence
-	// affirmed by c64 PRG p269
-	cld
+	// uses the following initial reset sequence, affirmed by c64 PRG p269
+#if !HAS_BCD_SAFE_RESET
+	cld // for CPUs having undefined D flag after reset
+#endif
 	ldx #$FF
 	txs
 	sei