llvm dev - May 2004 - [LLVMdev] opt, llcc, ll++, -O1, -O2, -O3

> For example: 
> $ llvmgcc ackerman.c -o ackerman -Wl,-native-cbe 
 
BTW, Chris, what should be then an analogy 
of "gcc -O3 -S foo.c" in LLVM framework?  
 
The invocation of 
 
 $ llvmgcc -S ackerman.c -o ackerman -Wl,-native-cbe  
 
does not produce native assebler output as one might expect. 
 
-- 
Valery

Valery A.Khamenya wrote:
>>For example: 
>>$ llvmgcc ackerman.c -o ackerman -Wl,-native-cbe 
> 
>  
> BTW, Chris, what should be then an analogy 
> of "gcc -O3 -S foo.c" in LLVM framework?  
>  
> The invocation of 
>  
>  $ llvmgcc -S ackerman.c -o ackerman -Wl,-native-cbe  
>  
> does not produce native assebler output as one might expect. 
>  
If you're wanting native assembler code, one way to do it would be:

llvmgcc -o ackerman ackerman.c # Produces ackerman.bc, a linked LLVM
                                # bytecode file
llc -o ackerman.s ackerman.bc  # Generates native assembly from linked
                                # LLVM bytecode


Note that this will statically link all of the library functions in libc 
that are currently available as LLVM bytecode, so this file may be a 
little large.

If you want the native code for only the code in ackerman.c, just 
replace the first line with:

llvmgcc -c -o ackerman.bc ackerman.c # Compiles but doesn't link

-- John T.

-- 
*********************************************************************
* John T. Criswell                         Email: criswell at uiuc.edu *
* Research Programmer                                               *
* University of Illinois at Urbana-Champaign                        *
*                                                                   *
* "It's today!" said Piglet. "My favorite day," said
Pooh.          *
*********************************************************************

On Wed, 5 May 2004, John Criswell wrote:
> Valery A.Khamenya wrote:
> >>For example:
> >>$ llvmgcc ackerman.c -o ackerman -Wl,-native-cbe
> >
> >
> > BTW, Chris, what should be then an analogy
> > of "gcc -O3 -S foo.c" in LLVM framework?
> >
> > The invocation of
> >
> >  $ llvmgcc -S ackerman.c -o ackerman -Wl,-native-cbe
> >
> > does not produce native assebler output as one might expect.
> >
>
> If you're wanting native assembler code, one way to do it would be:
>
> llvmgcc -o ackerman ackerman.c # Produces ackerman.bc, a linked LLVM
>                                 # bytecode file
> llc -o ackerman.s ackerman.bc  # Generates native assembly from linked
>                                 # LLVM bytecode
Alternatively, if you'd like to get native code with the C backend, you
should replace the llc line with:

llc -o ackerman.cbe.c ackerman.bc -march=c
gcc -O3 ackerman.cbe.c -o ackerman.s -S


Oh, and if you're playing with the LLVM native code generators, consider
adding the -regalloc=linearscan option.  Not doing so will make the code
really horrible.  :)

-Chris

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