https://gcc.gnu.org/bugzilla/show_bug.cgi?id=127420
--- Comment #6 from H.J. Lu <hjl.tools at gmail dot com> --- (In reply to Haochen Jiang from comment #4) > (In reply to Hongtao Liu from comment #3) > > (In reply to Richard Biener from comment #2) > > > With profile information (autofdo lbr) we might know the most likely > > > target, > > > we also know whether this is a computed goto which is the only case where > > > we > > > can easily re-order blocks to have the destination follow the branch. In > > > the > > > computed goto case we should have an abnormal edge to it, possibly > > > annotated > > > with a frequency. > > > > > > I wonder if we can measure how many cases we slow down by emitting UD2? > > > > Interesting, we can do some investigation with SPEC to see how many indirect > > jump target it's fallthru instruction. > > Assisted by AI, I tried with taking samples for SPEC run to see how many of > them. The ratio compiler generated indirect jump actually turning out to be > "FALLTHRU" effect sampled versus compiler generated indirect jump. > > For SPEC2017, it is about 7.77%. For SPEC2026, it is 2.91%. But it varies a > lot between benchmarks. The largest benchmarks based on ratio is 735.gem5_r > and 734.vpr_r, with 26.70% and 23.47%. All >5% benchmarks are shown below: > What are typical cases? Are they C++ programs?
