[LLVMdev] What are the optimizations that gold uses during the final link stage?

[Guoliang Jin]

  Hi,

I am using gold plugin with the option "-use-gold-plugin 
-Wl,-plugin-opt=also-emit-llvm" to compile apache.

I objdumped the final executable httpd to httpd.S.

I also compiled those per file bytecode into native code using the 
following:
llc filename.o
llvm-gcc -c filename.o.s -o filename.o.o

Then I objdumped filename.o.o to filename.o.S and compared some 
functions between httpd.S. and filename.o.S, and I found the order of 
some instructions are different.

Is this the expected behavior, probably because of some optimization 
during the final link stage? If this is the case, can you point me what 
those optimizations are, so that I could also apply them while compiling 
per file bytecode to native code.

Or am I using the wrong way to compile per file bytecode to native code?

Thanks,
Guoliang