diff options
Diffstat (limited to 'subx')
| -rw-r--r-- | subx/014indirect_addressing.cc | 76 |
1 files changed, 69 insertions, 7 deletions
diff --git a/subx/014indirect_addressing.cc b/subx/014indirect_addressing.cc index ee4b7494..bf00747a 100644 --- a/subx/014indirect_addressing.cc +++ b/subx/014indirect_addressing.cc @@ -188,21 +188,83 @@ case 0x2b: { // subtract r/m32 from r32 const uint8_t arg1 = (modrm>>3)&0x7; trace(Callstack_depth+1, "run") << "subtract r/m32 from " << rname(arg1) << end(); const int32_t* signed_arg2 = effective_address(modrm); - int64_t signed_full_result = Reg[arg1].i - *signed_arg2; - Reg[arg1].i -= *signed_arg2; - trace(Callstack_depth+1, "run") << "storing 0x" << HEXWORD << Reg[arg1].i << end(); - SF = (Reg[arg1].i < 0); - ZF = (Reg[arg1].i == 0); - OF = (Reg[arg1].i != signed_full_result); + const int32_t signed_result = Reg[arg1].i - *signed_arg2; + int64_t signed_full_result = static_cast<int64_t>(Reg[arg1].i) - *signed_arg2; + SF = (signed_result < 0); + ZF = (signed_result == 0); + OF = (signed_result != signed_full_result); // set CF uint32_t unsigned_arg2 = static_cast<uint32_t>(*signed_arg2); uint32_t unsigned_result = Reg[arg1].u - unsigned_arg2; - uint64_t unsigned_full_result = Reg[arg1].u - unsigned_arg2; + uint64_t unsigned_full_result = static_cast<uint64_t>(Reg[arg1].u) - unsigned_arg2; CF = (unsigned_result != unsigned_full_result); trace(Callstack_depth+1, "run") << "SF=" << SF << "; ZF=" << ZF << "; CF=" << CF << "; OF=" << OF << end(); + Reg[arg1].i = signed_result; + trace(Callstack_depth+1, "run") << "storing 0x" << HEXWORD << Reg[arg1].i << end(); break; } +:(code) +void test_subtract_mem_at_r32_from_r32_signed_overflow() { + Reg[EAX].i = 0x2000; + Reg[EBX].i = 0x80000000; // smallest negative signed integer + run( + "== 0x1\n" // code segment + // op ModR/M SIB displacement immediate + " 2b 18 \n" // subtract *EAX from EBX + // ModR/M in binary: 11 (direct mode) 011 (src EBX) 000 (dest EAX) + "== 0x2000\n" // data segment + "ff ff ff 7f\n" // largest positive signed integer + ); + CHECK_TRACE_CONTENTS( + "run: subtract r/m32 from EBX\n" + "run: effective address is 0x00002000 (EAX)\n" + "run: effective address contains 7fffffff\n" + "run: SF=0; ZF=0; CF=0; OF=1\n" + "run: storing 0x00000001\n" + ); +} + +void test_subtract_mem_at_r32_from_r32_unsigned_overflow() { + Reg[EAX].i = 0x2000; + Reg[EBX].i = 0; + run( + "== 0x1\n" // code segment + // op ModR/M SIB displacement immediate + " 2b 18 \n" // subtract *EAX from EBX + // ModR/M in binary: 11 (direct mode) 011 (src EBX) 000 (dest EAX) + "== 0x2000\n" // data segment + "01 00 00 00\n" // 1 + ); + CHECK_TRACE_CONTENTS( + "run: subtract r/m32 from EBX\n" + "run: effective address is 0x00002000 (EAX)\n" + "run: effective address contains 1\n" + "run: SF=1; ZF=0; CF=1; OF=0\n" + "run: storing 0xffffffff\n" + ); +} + +void test_subtract_mem_at_r32_from_r32_signed_and_unsigned_overflow() { + Reg[EAX].i = 0x2000; + Reg[EBX].i = 0; + run( + "== 0x1\n" // code segment + // op ModR/M SIB displacement immediate + " 2b 18 \n" // subtract *EAX from EBX + // ModR/M in binary: 11 (direct mode) 011 (src EBX) 000 (dest EAX) + "== 0x2000\n" // data segment + "00 00 00 80\n" // smallest negative signed integer + ); + CHECK_TRACE_CONTENTS( + "run: subtract r/m32 from EBX\n" + "run: effective address is 0x00002000 (EAX)\n" + "run: effective address contains 80000000\n" + "run: SF=1; ZF=0; CF=1; OF=1\n" + "run: storing 0x80000000\n" + ); +} + //:: and :(code) void test_and_r32_with_mem_at_r32() { |