Zdenek Kotala <Zdenek.Kotala@Sun.COM> writes:
> "-xO4 -xalias_level=basic" generates problem.
> "-xO3 -xalias_level=basic" works fine
> "-xO5" works fine
> As documentation say:
> Cite from Sun studio compiler guide:
> http://docs.sun.com/app/docs/doc/819-5265/bjapp?a=view
> xalias_level=basic
> ------------------
> If you use the -xalias_level=basic option, the compiler assumes that
> memory references that involve different C basic types do not alias each
> other. The compiler also assumes that references to all other types can
> alias each other as well as any C basic type. The compiler assumes that
> references using char * can alias any other type.
> For example, at the -xalias_level=basic level, the compiler assumes that
> a pointer variable of type int * is not going to access a float object.
> Therefore it is safe for the compiler to perform optimizations that
> assume a pointer of type float * will not alias the same memory that is
> referenced with a pointer of type int *.
I think you need to turn that off. On gcc we use -fno-strict-aliasing
which disables the type of compiler assumption that this is talking about.
I'm not sure exactly how that might create the specific failure we are
seeing here, but I can point you to lots and lots of places in the
sources where such an assumption would break things.
regards, tom lane