git.y1.nz

commit b66676b6b758177581139b151bce34952c7ca74a
parent 39e22ef511057c825e046fe31d6e6075a8269802
Author: Toxa <56631470+untoxa@users.noreply.github.com>
Date:   Wed,  2 Nov 2022 13:27:58 +0400

Merge pull request #438 from michel-iwaniec/nes_fast_div_and_mod

NES: Add FAST_DIV8 / FAST_MOD8 macros
Diffstat:
M
gbdk-lib/libc/targets/mos6502/nes/global.s
23
+++++++++++++++++++++++

1 file changed, 23 insertions(+), 0 deletions(-)
diff --git a/gbdk-lib/libc/targets/mos6502/nes/global.s b/gbdk-lib/libc/targets/mos6502/nes/global.s
@@ -119,3 +119,26 @@
         ;; Main user routine
         .globl  _main
 
+.macro DIV_PART divident divisor ?lbl
+        rol divident
+        rol
+        sec
+        sbc divisor
+        bcs lbl
+        adc divisor
+lbl:
+.endm
+.macro FAST_DIV8 divident divisor
+        ; returns quotient in A
+        .rept 8
+                DIV_PART divident divisor
+        .endm
+        lda divident
+        eor #0xFF
+.endm
+.macro FAST_MOD8 divident divisor
+        ; returns modulus in A
+        .rept 8
+                DIV_PART divident divisor
+        .endm
+.endm

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