[LLVMdev] main, prologue & call

Chris Lattner
Thu, 25 Dec 2003 01:56:00 -0000

> I don't understand exactlly the difference among main function,
prologue
> code, and call function.

I'm not sure that I understand your question.  LLVM abstracts away
target-specific information like function prologs and epilogs.

If you are curious about the typical arrangement used by unix systems with
_start and main, LLVM does not have that.  Basically it uses 'main' as
the
entry point to the program, allowing the system specific _start to set up
the system specific stuff it has to in a normal system, without llvm
having to know about it.  This is typically pulled in from the native libc
or crt0.o.

> how the llvm JIT process them in details?
> the main function is a program start entry

To start a program, the JIT code generates the main function, then jumps
to it to start execution.

> prologue code
> call

I'm not sure exactly what you mean here...

-Chris

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