On Wed, Aug 18, 2010 at 11:53 AM, Alain Ketterlin <alain.ketter...@gmail.com> wrote: > > I'm working on decompiling x86-64 binary programs, using branches to rebuild > a control-flow graph and looking for loops. I've found a significant number > of irreducible loops in gcc-produced code (irreducible loops are loops with > more than one entry point), especially in -O3 optimized binaries, even when > the source code is "well" structured. My experiments are done mainly on the > SPEC CPU-2006 benchmarks. > > My question is: where do these irreducible loops come from? Which > optimization pass leads to irreducible regions? Thanks in advance for any > pointer.
Questions right back at you: What compiler version are you using? Got a specific exampe (test case)? In older releases of GCC4, jump threading sometimes resulted in irreducible regions, but more recent GCCs carefully try to avoid them. Ciao! Steven
