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Z80: the delay-loop shortcut counts the DEC cycles of each skipped iteration

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The TIME_LOOP_HACKS shortcut skips the iterations of a
DEC rr / LD A,r / OR r / JR NZ (or JP NZ) delay loop by burning their
cycles in one go. Each skipped iteration runs four opcodes (R is
advanced by 4), but only LD, OR and the jump were counted: the DEC was
left out, so every iteration took 6 cycles too few (20 instead of 26
with JR) and such delays ran about 23% short.

Count the DEC as well, for the BC, DE and HL loops with JR and JP.

Co-Authored-By: Claude Opus 5.5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01N3fzdsnzkQVtgYtYzqepjX
This commit is contained in:
Claude committed 2026-10-29 18:16:53 +01:00
1 parent ff5f1bd024
commit f80f7223f4
1 file changed
+6
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src/cpu/z80/z80.c
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@@ -3487,6 +3487,7 @@ if( _BC > 1 && _PCD < 0xfffc ) { \
if( op3==0x20 && op4==0xfb ) \
{ \
int cnt = \
cc[Z80_TABLE_op][0x0b] + \
cc[Z80_TABLE_op][0x78] + \
cc[Z80_TABLE_op][0xb1] + \
cc[Z80_TABLE_op][0x20] + \
@@ -3505,6 +3506,7 @@ if( _BC > 1 && _PCD < 0xfffc ) { \
if( (ad1 + 256 * ad2) == (_PCD - 1) ) \
{ \
int cnt = \
cc[Z80_TABLE_op][0x0b] + \
cc[Z80_TABLE_op][0x78] + \
cc[Z80_TABLE_op][0xb1] + \
cc[Z80_TABLE_op][0xc2] + \
@@ -3530,6 +3532,7 @@ if( _DE > 1 && _PCD < 0xfffc ) { \
if( op3==0x20 && op4==0xfb ) \
{ \
int cnt = \
cc[Z80_TABLE_op][0x1b] + \
cc[Z80_TABLE_op][0x7a] + \
cc[Z80_TABLE_op][0xb3] + \
cc[Z80_TABLE_op][0x20] + \
@@ -3548,6 +3551,7 @@ if( _DE > 1 && _PCD < 0xfffc ) { \
if( (ad1 + 256 * ad2) == (_PCD - 1) ) \
{ \
int cnt = \
cc[Z80_TABLE_op][0x1b] + \
cc[Z80_TABLE_op][0x7a] + \
cc[Z80_TABLE_op][0xb3] + \
cc[Z80_TABLE_op][0xc2] + \
@@ -3573,6 +3577,7 @@ if( _HL > 1 && _PCD < 0xfffc ) { \
if( op3==0x20 && op4==0xfb ) \
{ \
int cnt = \
cc[Z80_TABLE_op][0x2b] + \
cc[Z80_TABLE_op][0x7c] + \
cc[Z80_TABLE_op][0xb5] + \
cc[Z80_TABLE_op][0x20] + \
@@ -3591,6 +3596,7 @@ if( _HL > 1 && _PCD < 0xfffc ) { \
if( (ad1 + 256 * ad2) == (_PCD - 1) ) \
{ \
int cnt = \
cc[Z80_TABLE_op][0x2b] + \
cc[Z80_TABLE_op][0x7c] + \
cc[Z80_TABLE_op][0xb5] + \
cc[Z80_TABLE_op][0xc2] + \