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IDIV adjustments recommended by Allofich

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Jonathan Campbell
2021-11-01 09:33:22 -07:00
parent cad6d9b601
commit 0db764dae7
1 changed files with 14 additions and 6 deletions
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20
src/cpu/instructions.h
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@@ -709,7 +709,15 @@ extern bool enable_fpu;
* which would allow -32768 to work.
*
* The 8086 cannot ever trigger IDIVD so IDIVD does not need to check for the 8086
* case. */
* case.
*
* Note Microsoft Flight Simulator 1.0 is affected here because of some internal math
* like FD28000h / 1FA5h = 8000h which is technically incorrect because the result
* is 32768, not -32768 [https://github.com/joncampbell123/dosbox-x/commit/9be458ba0689d8c60c962808ead4cb11b99c6740].
*
* Some confusion exists here whether to throw an exception for x / y = 32768, and
* whether to throw an exception for x / y = -32768, more testing is needed on 8086
* and 386 processors. */
#define IDIVB(op1,load,save) \
{ \
@@ -718,8 +726,8 @@ extern bool enable_fpu;
Bits quo=((int16_t)reg_ax) / val; \
int8_t rem=(int8_t)((int16_t)reg_ax % val); \
int8_t quo8s=(int8_t)(quo&0xff); \
if (CPU_CORE == CPU_ARCHTYPE_8086 && quo == -0x80) EXCEPTION(0); \
if (quo!=(int16_t)quo8s) EXCEPTION(0); \
if (CPU_CORE == CPU_ARCHTYPE_8086 && (quo == -0x80 || quo == 0x80)) EXCEPTION(0); \
if (quo!=(int16_t)quo8s && (CPU_CORE == CPU_ARCHTYPE_8086 || quo != 0x80)) EXCEPTION(0); \
reg_ah=(uint8_t)rem; \
reg_al=(uint8_t)quo8s; \
FillFlags(); \
@@ -740,8 +748,8 @@ extern bool enable_fpu;
Bits quo=num/val; \
int16_t rem=(int16_t)(num % val); \
int16_t quo16s=(int16_t)(quo&0xffff); \
if (CPU_CORE == CPU_ARCHTYPE_8086 && quo == -0x8000) EXCEPTION(0); \
if (quo!=(int32_t)quo16s) EXCEPTION(0); \
if (CPU_CORE == CPU_ARCHTYPE_8086 && (quo == -0x8000 || quo == 0x8000)) EXCEPTION(0); \
if (quo!=(int32_t)quo16s && (CPU_CORE == CPU_ARCHTYPE_8086 || quo != 0x8000)) EXCEPTION(0); \
reg_dx=(uint16_t)rem; \
reg_ax=(uint16_t)quo16s; \
FillFlags(); \
@@ -761,7 +769,7 @@ extern bool enable_fpu;
int64_t quo=num/val; \
int32_t rem=(int32_t)(num % val); \
int32_t quo32s=(int32_t)(quo&0xffffffff); \
if (quo!=(int64_t)quo32s) EXCEPTION(0); \
if (quo!=(int64_t)quo32s && (quo != 0x80000000)) EXCEPTION(0); \
reg_edx=(uint32_t)rem; \
reg_eax=(uint32_t)quo32s; \
FillFlags(); \