On Wed, Feb 01, 2006 at 09:26:57AM -0800, Michael Uhler wrote: > Daniel, > > The O/S maybe doing something different, but the architecture has 3 bits in > Status: KX, SX, and UX that enable access to the address space above 32 > bits. With these bits off, an attempt to access these addresses causes an > exception. So while 32-bit apps have the full 64-bit address space, most of > it is inaccessible to the 32-bit app. That's not actually what I was referring to: there's at least one MIPS implementation where the results of 32-bit arithmetic operations are not just architecturally unpredictable but actually wrong if the upper bits are not properly sign extended (I might be misremembering, but I think I'm talking about the SB-1). That's the sort of thing that can be basically impossible to track down if your debugger doesn't show you the whole register. -- Daniel Jacobowitz CodeSourcery
