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//: instructions that (immediately) contain an argument to act with
:(scenario add_imm32_to_r32)
% Reg[3].i = 1;
# op ModRM SIB displacement immediate
81 c3 0a 0b 0c 0d # add 0x0d0c0b0a to EBX (reg 3)
+run: combine imm32 0x0d0c0b0a with effective address
+run: effective address is reg 3
+run: subop add
+run: storing 0x0d0c0b0b
:(before "End Single-Byte Opcodes")
case 0x81: { // combine imm32 with r/m32
uint8_t modrm = next();
int32_t arg2 = imm32();
trace(2, "run") << "combine imm32 0x" << HEXWORD << arg2 << " with effective address" << end();
int32_t* arg1 = effective_address(modrm);
uint8_t subop = (modrm>>3)&0x7; // middle 3 'reg opcode' bits
switch (subop) {
case 0:
trace(2, "run") << "subop add" << end();
BINARY_ARITHMETIC_OP(+, *arg1, arg2);
break;
// End Op 81 Subops
default:
cerr << "unrecognized sub-opcode after 81: " << NUM(subop) << '\n';
exit(1);
}
break;
}
//:
:(scenario add_imm32_to_mem_at_r32)
% Reg[3].i = 0x60;
% Mem.at(0x60) = 1;
# op ModR/M SIB displacement immediate
81 03 0a 0b 0c 0d # add 0x0d0c0b0a to *EBX (reg 3)
+run: combine imm32 0x0d0c0b0a with effective address
+run: effective address is mem at address 0x60 (reg 3)
+run: subop add
+run: storing 0x0d0c0b0b
//:: subtract
:(scenario subtract_imm32_from_eax)
% Reg[EAX].i = 0x0d0c0baa;
# op ModR/M SIB displacement immediate
2d 0a 0b 0c 0d # subtract 0x0d0c0b0a from EAX (reg 0)
+run: subtract imm32 0x0d0c0b0a from reg EAX
+run: storing 0x000000a0
:(before "End Single-Byte Opcodes")
case 0x2d: { // subtract imm32 from EAX
int32_t arg2 = imm32();
trace(2, "run") << "subtract imm32 0x" << HEXWORD << arg2 << " from reg EAX" << end();
BINARY_ARITHMETIC_OP(-, Reg[EAX].i, arg2);
break;
}
//:
:(scenario subtract_imm32_from_mem_at_r32)
% Reg[3].i = 0x60;
% Mem.at(0x60) = 10;
# op ModRM SIB displacement immediate
81 2b 01 00 00 00 # subtract 1 from *EBX (reg 3)
+run: combine imm32 0x00000001 with effective address
+run: effective address is mem at address 0x60 (reg 3)
+run: subop subtract
+run: storing 0x00000009
//:
:(scenario subtract_imm32_from_r32)
% Reg[3].i = 10;
# op ModRM SIB displacement immediate
81 eb 01 00 00 00 # subtract 1 from EBX (reg 3)
+run: combine imm32 0x00000001 with effective address
+run: effective address is reg 3
+run: subop subtract
+run: storing 0x00000009
:(before "End Op 81 Subops")
case 5: {
trace(2, "run") << "subop subtract" << end();
BINARY_ARITHMETIC_OP(-, *arg1, arg2);
break;
}
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