Hi, I'm Alex Tzannes and I am porting GCC 4.0.2 to a new experimental parallel architecture. Here's one issue I don't know how to go about. The ISA of our machine is based on MIPS (so I made a copy of the MIPS back end and have been modifying that). One conceptual difference is that the machine can be either in serial mode or in parallel mode. The switch from serial to parallel happens with a 'spawn' instruction, and the swich from parallel to serial with a 'join' instruction. This is important because the ISA instructions that can be used in serial and in parallel mode are different !
For example let's say mvtg is an instruction that can only be used in 'serial mode'. I currently have a template in the back end (.md file) that generates that instruction when it is needed. The only thing I don't know how to check is that it is only generated in serial mode. Instruction attributes do not seem like the solution because there seems to be no other way to set them besides in the RTL rules in the .md file (which is too late; I would want to read the information at that point). Is there a way to annotate each RTL instruction and to check that during code generation ? Has a similar problem been solved in some other back-end? Thank you, Alex
