On Wed, Dec 13, 2023 at 3:47 PM Eduard Zingerman <eddyz87@xxxxxxxxx> wrote: > > On Wed, 2023-12-13 at 15:40 -0800, Andrii Nakryiko wrote: > [...] > > > 24: (18) r2 = 0x4 ; R2_w=4 > > > 26: (7e) if w8 s>= w0 goto pc+5 > > > mark_precise: frame0: last_idx 26 first_idx 22 subseq_idx -1 > > > mark_precise: frame0: regs=r5,r8 stack= before 24: (18) r2 = 0x4 > > > ... ^^^^^^^^^^ > > > ^^^^^^^^^^ > > > Here w8 == 15, w0 in range [0, 2], so the jump is being predicted, > > > but for some reason R0 is not among the registers that would be marked precise. > > > > It is, as a second step. There are two concatenated precision logs: > > > > mark_precise: frame0: last_idx 26 first_idx 22 subseq_idx -1 > > mark_precise: frame0: regs=r0 stack= before 24: (18) r2 = 0x4 > > mark_precise: frame0: regs=r0 stack= before 23: (bf) r5 = r8 > > mark_precise: frame0: regs=r0 stack= before 22: (67) r4 <<= 2 > > > > > > The issue is elsewhere, see my last email. > > Oh, right, there are two calls to mark_chain_precision in a row, thanks We should probably combine those two steps, though, backtrack_state allows us that now (see how propagate_precision() is doing that in one go). It used to be very hard to mark two registers at the same time, but now it's trivial. So not a bad idea to improve this and remove confusion, especially in big real-world programs.
