llvm dev - Aug 2006 - [LLVMdev] updating the "Getting Started" page with more info about the gcc4 frontend

On Wed, Aug 23, 2006 at 06:38:36PM -0700, Scott Michel
wrote:
> There should also be a large notice in 40 point font and bold that says,
> "gcc4 does not produce byte code by default: you must use the
-emit-llvm
> flag to get LLVM byte code."
=)

Where -is- that documented?

The only reason I know about it is because of how many times it's come
up on the list.  =)

(Which doesn't help people who don't read the list)

--Emil

On Aug 23, 2006, at 7:00 PM, Emil Mikulic wrote:
> Where -is- that documented?
>
> The only reason I know about it is because of how many times it's come
> up on the list.  =)
http://llvm.org/docs/GettingStarted.html ?

...
Example with llvm-gcc4
First, create a simple C file, name it 'hello.c':
   #include <stdio.h>
   int main() {
     printf("hello world\n");
     return 0;
   }

Next, compile the C file into a native executable:
% llvm-gcc hello.c -o hello
Note that llvm-gcc works just like GCC by default. The standard -S and  
-c arguments work as usual (producing a native .s or .o file,  
respectively).
Next, compile the C file into a LLVM bytecode file:
% llvm-gcc -O3 -emit-llvm hello.c -c -o hello.bc
The -emit-llvm option can be used with the -S or -c options to emit an  
LLVM ".ll" or ".bc" file (respectively) for the code. This
allows you
to use the standard LLVM tools on the bytecode file.
Unlike llvm-gcc3, llvm-gcc4 correctly responds to -O[0123] arguments.
...

Devang Patel wrote:
> 
> On Aug 23, 2006, at 7:00 PM, Emil Mikulic wrote:
> 
>> Where -is- that documented?
>>
>> The only reason I know about it is because of how many times it's
come
>> up on the list.  =)
> 
> http://llvm.org/docs/GettingStarted.html ?
> 
> ...
> Example with llvm-gcc4
> First, create a simple C file, name it 'hello.c':
>   #include <stdio.h>
>   int main() {
>     printf("hello world\n");
>     return 0;
>   }
> 
> Next, compile the C file into a native executable:
That part about "native" -- yeah, it's there. The existence
predicate
returns true. IT'S SOMETHING THAT IS EASILY SKIPPED OVER WHEN SKIMMING
THE DOCUMENT BECAUSE, HECK, THE GCC3 DRIVER COMPILES DIRECTLY TO
BYTECODE SO WHY DOESNT GCC4?

It's a "least surprise" issue. If gcc3 produces bytecode directly,
why
did the gcc4 driver create such a large departure from original,
expected functionality? It's a rhetorical question, BTW.