Advanced Micro Devices Inc (AMD)

[Petz]

Because the compiler cannot see anything about the dynamic execution of a program or know what is in the registers when a subroutine is called from diverse places in a huge programming project.

My mind was on a different page than yours. I was discussing whether having a huge number of addressable, non-hidden registers can eliminate storage of intermediate results in temporary memory variables. This applies to Itanium which doesn't use OOO execution.

With that many registers you might think you never need a temp variable. But, no, the compiler can't just willy nilly use any register unless it saves it and restores it on exit.

Having a huge number of registers is necessary for the Itanium architecture so that new results don't overwrite old results that are still needed for other computations. On an x86 OOO machine, the CPU does this automatically by having many hidden registers and "knowing" exactly what is in each one.

Petz