Re: gcc-2.95.2 problem with target powerpc-eabi

[David Edelsohn]

>>>>> "Christoph Hirzel" writes:
Christoph> There seems to be a problem in copying 64 Bit integers
Christoph> or structures with gcc-2.95.2 for target powerpc-eabi.
Christoph> If I compile the following code for a PowerPC 603
Christoph> (option -mcpu=3D603)

Christoph> unsigned long long u1;
Christoph> unsigned long long u2;

Christoph> void Test()
Christoph> {
Christoph> u1 =3D u2;
Christoph> }

Christoph> the compiler generates the following assembler code

Christoph> lis 11,address@hidden
Christoph> la 9,address@hidden(11)
Christoph> lis 10,address@hidden
Christoph> la 11,address@hidden(10)
Christoph> lfd 0,0(11)
Christoph> stfd 0,0(9)

Christoph> The compiler seems to optimize the copy by using load (lfd)
Christoph> and store (stfd) double float instructions.

Christoph> Now my question. How can I avoid this, without using the
Christoph> compiler option -msoft-float ?
Christoph> I think it should be possible if I make some adjustmenst
Christoph> in the rs6000.md /.c /.h files and then rebuild the compiler.

Christoph> Has anybody any experience in doing this ?

        The current development version of GCC has the behavior you want
due to some other heuristic changes.  It is not a trivial change because
GCC needs to be able to store integers in FPRs due to fp conversion.  Once
it is allowed, GCC will use it where convenient, like moving a structure
or long long value.

David
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David Edelsohn                                      T.J. Watson Research Center
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