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UserspaceEmulator: Fix buggy IDIV instructions

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These were not doing mashing together the signed double-size results
correctly and lost bits in the signed/unsigned casting process.
This commit is contained in:
Andreas Kling 2020-07-18 17:29:50 +02:00
parent 9e6d002660
commit e4b068aec5
1 changed files with 24 additions and 7 deletions
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31
DevTools/UserspaceEmulator/SoftCPU.cpp
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@ -1257,18 +1257,35 @@ void SoftCPU::ESCAPE(const X86::Instruction&)
} }
void SoftCPU::HLT(const X86::Instruction&) { TODO(); } void SoftCPU::HLT(const X86::Instruction&) { TODO(); }
void SoftCPU::IDIV_RM16(const X86::Instruction&) { TODO(); }
void SoftCPU::IDIV_RM32(const X86::Instruction& insn) void SoftCPU::IDIV_RM16(const X86::Instruction& insn)
{ {
auto divisor = insn.modrm().read32(*this, insn); auto divisor = (i16)insn.modrm().read16(*this, insn);
if (divisor == 0) { if (divisor == 0) {
warn() << "Divide by zero"; warn() << "Divide by zero";
TODO(); TODO();
} }
i64 dividend = ((i64)edx() << 32) | eax(); i32 dividend = (i32)(((u32)dx() << 16) | (u32)ax());
auto result = dividend / divisor; i32 result = dividend / divisor;
if (result > NumericLimits<i32>::max()) { if (result > NumericLimits<i16>::max() || result < NumericLimits<i16>::min()) {
warn() << "Divide overflow";
TODO();
}
set_ax(result);
set_dx(dividend % divisor);
}
void SoftCPU::IDIV_RM32(const X86::Instruction& insn)
{
auto divisor = (i32)insn.modrm().read32(*this, insn);
if (divisor == 0) {
warn() << "Divide by zero";
TODO();
}
i64 dividend = (i64)(((u64)edx() << 32) | (u64)eax());
i64 result = dividend / divisor;
if (result > NumericLimits<i32>::max() || result < NumericLimits<i32>::min()) {
warn() << "Divide overflow"; warn() << "Divide overflow";
TODO(); TODO();
} }
@ -1279,7 +1296,7 @@ void SoftCPU::IDIV_RM32(const X86::Instruction& insn)
void SoftCPU::IDIV_RM8(const X86::Instruction& insn) void SoftCPU::IDIV_RM8(const X86::Instruction& insn)
{ {
auto divisor = (i16)insn.modrm().read8(*this, insn); auto divisor = (i8)insn.modrm().read8(*this, insn);
if (divisor == 0) { if (divisor == 0) {
warn() << "Divide by zero"; warn() << "Divide by zero";
TODO(); TODO();