From: Peter Zijlstra > Sent: 04 June 2021 11:12 > > Hi! > > With optimizing compilers becoming more and more agressive and C so far > refusing to acknowledge the concept of control-dependencies even while > we keep growing the amount of reliance on them, things will eventually > come apart. > > There have been talks with toolchain people on how to resolve this; one > suggestion was allowing the volatile qualifier on branch statements like > 'if', but so far no actual compiler has made any progress on this. > > Rather than waiting any longer, provide our own construct based on that > suggestion. The idea is by Alan Stern and refined by Paul and myself. > > Code generation is sub-optimal (for the weak architectures) since we're > forced to convert the condition into another and use a fixed conditional > branch instruction, but shouldn't be too bad. What happens on mips-like architectures (I think includes riscv) that have 'compare two registers and branch' instructions rather than a more traditional 'flags register'? The generated code it likely to be somewhat different. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)
