Can you in some way implement assembly code in the middle of your C code?
Can you in some way implement assembly code in the middle of your C code?
It depends on what compiler you are using. Read the compiler's documentation on how to embed ASM code in your C program.
Isnt C just a higher level ASM?
Sorry for the off topic question, just i dont feel like googling it :P
Yes and no. If I recall, a compiler will transform C code into ASM code and then put the ASM code into binary form. Don't quote me on that though.
in gcc, but it's backwards worthless at&t syntax
With lots of extra stuff you can do, lookup inline-assembly with gcc.Code:asm("instruction"); asm("instruction\n\t" "instruction\n\t" ...);
in cl it's
A compiler transforms code into assembly which is english binary, a 1:1 translation which is then assembled and linked into an executable format like elf or exe.Code:__asm { asm stuff } __asm instruction
Assembly is the syntax of machine language.
Let's say return is 0x7F. So anywhere in an executable file you have 0x7F, disregarding prior context and any previous opcodes occurring, this would execute a return from a subroutine back to the caller.
But 0x7F could also represent an address, an offset into a segment, a segment, a portion of a descriptor, an immediate value, etc, etc.
Data is simply just numbers. It's how data is interpreted that matters.
A simple linear interpolation in x86 asm using the FPU.
Inline asmCode:proc LinearInterp ARGS v1:QWORD,v2:QWORD,Interp:QWORD push ebp mov ebp,esp fld [v2] fsub [v1] fmul [Interp] fadd [v1] pop ebp ret endp
Code:float LinearInterp(float v1,float v2,float Interp) { __asm { fld [v2] fsub [v1] fmul [Interp] fadd [v1] } return st(0); }
Last edited by VirtualAce; 06-26-2006 at 12:02 AM.
You can read this document if you are using Ms. Visual C++.
Link
>Isnt C just a higher level ASM?
No.
>If I recall, a compiler will transform C code into ASM code and
>then put the ASM code into binary form.
Not necessarily, though it's up to the compiler. It's generally easier to translate C into assembly and then assembly into machine code (gcc/as is a good example), but it's more efficient to translate C directly into machine code. Since compilation time is an issue among compiler writers, the most efficient way usually wins.
My best code is written with the delete key.
As opposed to the 'highly valuable' Intel syntax?Originally Posted by valis
In MS Visual C++, all assembly code is compiled 'as-is' without the compiler touching it. This is good and bad.
For one you have no idea what the state of the registers are upon entry to the asm block. You do not know which registers Visual Studio is using and for what reason prior to the asm block. I'm sure that Visual Studio may do a pushf and as well save all the register states, but this means that every inline block of asm would incur a slight amount of overhead due to the register/flags preservation.
Inline assembly can be good, but it is not always going to be faster than just doing the same code in C/C++. You must choose your battles wisely with inline assembly and examine the final assembly source in order to really see what is going on.
Use it with caution.
And yes, AT&T syntax sucks ass.
Often modern compilers will translate code into an intermediate, low level language that can resemble assembly in many respects (could resemble anything since it's just another language). This is done so that it may then easily be compiled to native assembly for many different architectures.If I recall, a compiler will transform C code into ASM code and then put the ASM code into binary form.
HA I love getting you guys talking and informing me on the good and bad :-)
Oh and I have to ask, what is AT&T syntax?
Is it worse the java?
Modern compilers under Windows will assemble to MSIL which is a pain in the arse. MSIL is MS's attempt to get all the languages to 'get along' with one another. It has nothing to do AFAIK with platform independence - a concept which I believe is not even in the vocabulary in Redmond, WA.
In a lot of compiler's there's an intermediate code generation phase in which your input (after being lexed, parsed and semantically checked; aka after being processed by the front end) is taken and translated into a 'easily readable, easily compilable' intermediate stage. The basic standard for this language is pretty much that it's easily readible and easy to generate machine code from. The reason a lot of compilers take this option is so that they can then optimize that intermediatary input as needed to still produce the correct ouput but do it in a more 'efficient' manner (although *how* the compiler optimizes it is really up to what you want these days, i.e. size vs. speed.) Also, this allows you to easily swap out the back end of the compiler (the part that generates the machine code) with another so you can port the compiler inbetween architectures. That is, you only have to rewrite a very small portion that is 'modular' rather than grounded to one specific architecture; it would be much easier to take an already existing compiler and swap out the part that generates x86 assembly with SPARC assembly rather than just rewrite the whole compiler to get it to work on a SPARC machine. A lot of people have gone through the trouble of making/researching compilers for several languages, who's front ends all generate the same intermediatary language so that you could for example, write Java code and C++ code and stick them together. This field has only made so much progress however, as there are all sorts of little semantic 'gotchas' that a language can throw at you. .NET is a very good attempt at language interoperability so far though (probably the best), but I will say it isn't perfect and there are things that still need to be done.
There's an intel option you can use that will let you use intel-based syntax in your inline assembly.in gcc, but it's backwards worthless at&t syntax
Assembly is the delineation of the processor's opcodes that it executes directly. Normally it is very processor specific, but it is also very tool specific which is why there isn't really a standard defined for using assembly on a certain machine. It all depends on what assembler and processor you're writing for.Assembly is the syntax of machine language.
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Well I prefer Intel syntax. It looks much cleaner and it makes more sense to me.As opposed to the 'highly valuable' Intel syntax?
lol I found that quite funny.Oh and I have to ask, what is AT&T syntax?
Is it worse the java?