b9dd48e34b
This adds support for StructArgument on s390x. The ABI for this platform requires that the address of the buffer holding the copy of the struct argument is passed from caller to callee as hidden pointer, using a register or overflow stack slot. To implement this, I've added an optional "pointer" filed to ABIArg::StructArg, and code to handle the pointer both in common abi_impl code and the s390x back-end. One notable change necessary to make this work involved the "copy_to_arg_order" mechanism. Currently, for struct args we only need to copy the data (and that need to happen before setting up any other args), while for non-struct args we only need to set up the appropriate registers or stack slots. This order is ensured by sorting the arguments appropriately into a "copy_to_arg_order" list. However, for struct args with explicit pointers we need to *both* copy the data (again, before everything else), *and* set up a register or stack slot. Since we now need to touch the argument twice, we cannot solve the ordering problem by a simple sort. Instead, the abi_impl common code now provided *two* callbacks, emit_copy_regs_to_buffer and emit_copy_regs_to_arg, and expects the back end to first call copy..to_buffer for all args, and then call copy.._to_arg for all args. This required updates to all back ends. In the s390x back end, in addition to the new ABI code, I'm now adding code to actually copy the struct data, using the MVC instruction (for small buffers) or a memcpy libcall (for larger buffers). This also requires a bit of new infrastructure: - MVC is the first memory-to-memory instruction we use, which needed a bit of memory argument tweaking - We also need to set up the infrastructure to emit libcalls. (This implements the first half of issue #4565.)
This crate contains the core Cranelift code generator. It translates code from an intermediate representation into executable machine code.