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ARM: Fix edge case with Thumb SBC flags (fixes #1818)

This commit is contained in:
Vicki Pfau 2020-07-12 14:26:13 -07:00
parent 9295c3c893
commit 007baef3b0
2 changed files with 12 additions and 3 deletions
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1
CHANGES
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@ -8,6 +8,7 @@ Emulation fixes:
- ARM: Fix STR storing PC after address calculation
- ARM: Fix LDM^ writeback to user-mode register
- ARM: Fix LDM^ {pc} differences (fixes mgba.io/i/1698)
- ARM: Fix edge case with Thumb SBC flags (fixes mgba.io/i/1818)
- GB: Partially fix timing for skipped BIOS
- GB Memory: Fix OAM DMA from top 8 kB
- GB MBC: Fix MBC1 mode changing behavior

14
src/arm/isa-thumb.c
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@ -25,6 +25,13 @@
cpu->cpsr.c = ARM_BORROW_FROM(M, N, D); \
cpu->cpsr.v = ARM_V_SUBTRACTION(M, N, D);
#define THUMB_SUBTRACTION_CARRY_S(M, N, D, C) \
cpu->cpsr.flags = 0; \
cpu->cpsr.n = ARM_SIGN(D); \
cpu->cpsr.z = !(D); \
cpu->cpsr.c = ARM_BORROW_FROM_CARRY(M, N, D, C); \
cpu->cpsr.v = ARM_V_SUBTRACTION(M, N, D);
#define THUMB_NEUTRAL_S(M, N, D) \
cpu->cpsr.n = ARM_SIGN(D); \
cpu->cpsr.z = !(D);
@ -203,10 +210,11 @@ DEFINE_DATA_FORM_5_INSTRUCTION_THUMB(ADC,
THUMB_ADDITION_S(d, n, cpu->gprs[rd]);)
DEFINE_DATA_FORM_5_INSTRUCTION_THUMB(SBC,
int n = cpu->gprs[rn] + !cpu->cpsr.c;
int n = cpu->gprs[rn];
int d = cpu->gprs[rd];
cpu->gprs[rd] = d - n;
THUMB_SUBTRACTION_S(d, n, cpu->gprs[rd]);)
cpu->gprs[rd] = d - n - !cpu->cpsr.c;
THUMB_SUBTRACTION_CARRY_S(d, n, cpu->gprs[rd], !cpu->cpsr.c);)
DEFINE_DATA_FORM_5_INSTRUCTION_THUMB(ROR,
int rs = cpu->gprs[rn] & 0xFF;
if (rs) {