middle-end/9725: Invalid dependency determination

[Wolfgang Bangerth]

> I was fearing you would say this. But I can in no way agree - the code
> presented is valid C, and hence should work at any optimization level.

What makes you think so? gcc's info pages show

`-fstrict-aliasing'
     Allows the compiler to assume the strictest aliasing rules
     applicable to the language being compiled.  For C (and C++), this
     activates optimizations based on the type of expressions.  In
     particular, an object of one type is assumed never to reside at
     the same address as an object of a different type, unless the
     types are almost the same.  For example, an `unsigned int' can
     alias an `int', but not a `void*' or a `double'.  A character type
     may alias any other type.

In your code you try to pretend that a variable of type "struct S" resides 
at the place of a long long. That's exactly the case that's covered above, 
which in turn exactly parallels what the standard says.

W.

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Wolfgang Bangerth             email:            bangerth@ticam.utexas.edu
                              www: http://www.ticam.utexas.edu/~bangerth/