llvm-project

45830769 - [compiler-rt][RISC-V] ILP32E/LP64E Save/Restore Grouping (#95398)

[compiler-rt][RISC-V] ILP32E/LP64E Save/Restore Grouping (#95398) This changes the save/restore procedures to save/restore registers one by one - to match the stack alignment for the ILP32E/LP64E ABIs, rather than the larger batches of the conventional ABIs. The implementations of the save routines are not tail-shared, to reduce the number of instructions. I think this also helps code size but I need to check this again. I would expect (but haven't measured) that the majority of functions compiled for the ILP32E/LP64E ABIs will in fact use both callee-saved registers, and therefore there are still savings to be had, but I think those can come later, with more data (especially if those changes are just to the instruction sequences we use to save the registers, rather than the number and alignment of how this is done). This is a potential break for all of the ILP32E/LP64E ABI - we may instead have to teach the compiler to emit the CFI information correctly for the grouping we already have implemented (because that grouping matches GCC). It depends on how intentional we think the grouping is in the original ILP32E/LP64E save/restore implementation was, and whether we think we can fix that now.