Can a C compiler generate an executable 64-bits where pointers are 32-bits?

Question

Most programs fits well on <4GB address space but needs to use new features just available on x64 architecture.

Are there compilers/platforms where I can use x64 regi

Answer 1

I think this would be similar to the MIPS n32 ABI: 64-bit registers with 32-bit pointers.

In the n32 ABI, all registers are 64-bit (so requires a MIPS64 processor). But addresses and pointers are only 32-bit (when stored in memory), decreasing the memory footprint. When loading a 32-bit value (such as a pointer) into a register, it is sign-extended into 64-bits. When the processor uses the pointer/address for a load or store, all 64-bits are used (the processor is not aware of the n32-ess of the SW). If your OS supports n32 programs (maybe the OS also follows the n32 model or it may be a proper 64-bit OS with added n32 support), it can locate all memory used by the n32 application in suitable memory (e.g. the lower 2GB and the higher 2GB, virtual addresses). The only glitch with this model is that when registers are saved on the stack (function calls etc), all 64-bits are used, there is no 32-bit data model in the n32 ABI.

Probably such an ABI could be implemented for x86-64 as well.