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How to extract 32bit numbers in assembly
How does the stack work in assembly language?How to view the assembly behind the code using Visual C++?How do I achieve the theoretical maximum of 4 FLOPs per cycle?cmp assembly language instruction - gas formatWhy does GCC generate 15-20% faster code if I optimize for size instead of speed?How assembly accesses/stores variables on the stackReplacing a 32-bit loop counter with 64-bit introduces crazy performance deviationsAssembling 32bit Assembly on 64bit MachineC++ code for testing the Collatz conjecture faster than hand-written assembly - why?Local variables in assembly — assembler not emitting `sub esp, X` instruction
I have a 32bit number stored on the top of the stack. And I would like to compare it with another number, something like:
cmp [rsp], 234
But I want both rsp and 234 to be treated as 32bit numbers, how can I do that (I am new to assembly)?
assembly x86-64
asked Mar 7 at 11:51
mikolmikol
245
add a comment |
I have a 32bit number stored on the top of the stack. And I would like to compare it with another number, something like:
cmp [rsp], 234
But I want both rsp and 234 to be treated as 32bit numbers, how can I do that (I am new to assembly)?
assembly x86-64
asked Mar 7 at 11:51
mikolmikol
245
6
Depends on your assembler butcmp dword [rsp], 234orcmp dword ptr [rsp], 234will usually do it.
– Jester
Mar 7 at 11:51
You don't actually wantrspto be treated as a 32-bit pointer. If you did want that, you'd write[esp]to get 32-bit address-size (and probably segfault because RSP normally has some high bits set, so truncating it to 32-bit doesn't produce a valid address. If you want the pointed-to memory[rsp]to be 32-bit, then do what Jester said.
– Peter Cordes
Mar 7 at 23:26
add a comment |
I have a 32bit number stored on the top of the stack. And I would like to compare it with another number, something like:
cmp [rsp], 234
But I want both rsp and 234 to be treated as 32bit numbers, how can I do that (I am new to assembly)?
assembly x86-64
asked Mar 7 at 11:51
mikolmikol
245
I have a 32bit number stored on the top of the stack. And I would like to compare it with another number, something like:
cmp [rsp], 234
But I want both rsp and 234 to be treated as 32bit numbers, how can I do that (I am new to assembly)?
assembly x86-64
assembly x86-64
asked Mar 7 at 11:51
mikolmikol
245
asked Mar 7 at 11:51
mikolmikol
245
asked Mar 7 at 11:51
mikolmikol
245
asked Mar 7 at 11:51
mikolmikol
245
asked Mar 7 at 11:51
mikolmikol
245
245
6
Depends on your assembler butcmp dword [rsp], 234orcmp dword ptr [rsp], 234will usually do it.
– Jester
Mar 7 at 11:51
You don't actually wantrspto be treated as a 32-bit pointer. If you did want that, you'd write[esp]to get 32-bit address-size (and probably segfault because RSP normally has some high bits set, so truncating it to 32-bit doesn't produce a valid address. If you want the pointed-to memory[rsp]to be 32-bit, then do what Jester said.
– Peter Cordes
Mar 7 at 23:26
add a comment |
6
Depends on your assembler butcmp dword [rsp], 234orcmp dword ptr [rsp], 234will usually do it.
– Jester
Mar 7 at 11:51
You don't actually wantrspto be treated as a 32-bit pointer. If you did want that, you'd write[esp]to get 32-bit address-size (and probably segfault because RSP normally has some high bits set, so truncating it to 32-bit doesn't produce a valid address. If you want the pointed-to memory[rsp]to be 32-bit, then do what Jester said.
– Peter Cordes
Mar 7 at 23:26
6
6
Depends on your assembler but
cmp dword [rsp], 234 or cmp dword ptr [rsp], 234 will usually do it.– Jester
Mar 7 at 11:51
Depends on your assembler but
cmp dword [rsp], 234 or cmp dword ptr [rsp], 234 will usually do it.– Jester
Mar 7 at 11:51
You don't actually want
rsp to be treated as a 32-bit pointer. If you did want that, you'd write [esp] to get 32-bit address-size (and probably segfault because RSP normally has some high bits set, so truncating it to 32-bit doesn't produce a valid address. If you want the pointed-to memory [rsp] to be 32-bit, then do what Jester said.– Peter Cordes
Mar 7 at 23:26
You don't actually want
rsp to be treated as a 32-bit pointer. If you did want that, you'd write [esp] to get 32-bit address-size (and probably segfault because RSP normally has some high bits set, so truncating it to 32-bit doesn't produce a valid address. If you want the pointed-to memory [rsp] to be 32-bit, then do what Jester said.– Peter Cordes
Mar 7 at 23:26
add a comment |
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6
Depends on your assembler but
cmp dword [rsp], 234orcmp dword ptr [rsp], 234will usually do it.– Jester
Mar 7 at 11:51
You don't actually want
rspto be treated as a 32-bit pointer. If you did want that, you'd write[esp]to get 32-bit address-size (and probably segfault because RSP normally has some high bits set, so truncating it to 32-bit doesn't produce a valid address. If you want the pointed-to memory[rsp]to be 32-bit, then do what Jester said.– Peter Cordes
Mar 7 at 23:26