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//: operating on memory at the address provided by some register
:(scenario add_r32_to_mem_at_r32)
% Reg[3].i = 0x10;
% Reg[0].i = 0x60;
# word in addresses 0x60-0x63 has value 1
% Mem.at(0x60) = 1;
# op ModR/M SIB displacement immediate
01 18 # add EBX (reg 3) to *EAX (reg 0)
+run: add reg 3 to effective address
+run: effective address is mem at address 0x60 (reg 0)
+run: storing 0x00000011
:(before "End Mod Special-cases")
case 0:
// mod 0 is usually indirect addressing
switch (rm) {
default:
trace(2, "run") << "effective address is mem at address 0x" << std::hex << Reg[rm].u << " (reg " << NUM(rm) << ")" << end();
assert(Reg[rm].u + sizeof(int32_t) <= Mem.size());
result = reinterpret_cast<int32_t*>(&Mem.at(Reg[rm].u)); // rely on the host itself being in little-endian order
break;
// End Mod 0 Special-cases
}
break;
//:
:(scenario add_mem_at_r32_to_r32)
% Reg[0].i = 0x60;
% Reg[3].i = 0x10;
% Mem.at(0x60) = 1;
# op ModR/M SIB displacement immediate
03 18 # add *EAX (reg 0) to EBX (reg 3)
+run: add effective address to reg 3
+run: effective address is mem at address 0x60 (reg 0)
+run: storing 0x00000011
:(before "End Single-Byte Opcodes")
case 0x03: { // add r/m32 to r32
uint8_t modrm = next();
uint8_t arg1 = (modrm>>3)&0x7;
trace(2, "run") << "add effective address to reg " << NUM(arg1) << end();
const int32_t* arg2 = effective_address(modrm);
BINARY_ARITHMETIC_OP(+, Reg[arg1].i, *arg2);
break;
}
//:: subtract
:(scenario sub_r32_from_mem_at_r32)
% Reg[0].i = 0x60;
% Mem.at(0x60) = 10;
% Reg[3].i = 1;
# op ModRM SIB displacement immediate
29 18 # subtract EBX (reg 3) from *EAX (reg 0)
+run: subtract reg 3 from effective address
+run: effective address is mem at address 0x60 (reg 0)
+run: storing 0x00000009
//:
:(scenario sub_mem_at_r32_from_r32)
% Reg[0].i = 0x60;
% Mem.at(0x60) = 1;
% Reg[3].i = 10;
# op ModRM SIB displacement immediate
2b 18 # subtract *EAX (reg 0) from EBX (reg 3)
+run: subtract effective address from reg 3
+run: effective address is mem at address 0x60 (reg 0)
+run: storing 0x00000009
:(before "End Single-Byte Opcodes")
case 0x2b: { // subtract r/m32 from r32
uint8_t modrm = next();
uint8_t arg1 = (modrm>>3)&0x7;
trace(2, "run") << "subtract effective address from reg " << NUM(arg1) << end();
const int32_t* arg2 = effective_address(modrm);
BINARY_ARITHMETIC_OP(-, Reg[arg1].i, *arg2);
break;
}
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