This patch removes hidden codegen flag -print-schedule effectively reverting the logic originally committed as r300311 (https://llvm.org/viewvc/llvm-project?view=revision&revision=300311).
Flag -print-schedule was originally introduced by r300311 to address PR32216 (https://bugs.llvm.org/show_bug.cgi?id=32216). That bug was about adding "Better testing of schedule model instruction latencies/throughputs".
These days, we can use llvm-mca to test scheduling models. So there is no longer a need for flag -print-schedule in LLVM. The main use case for PR32216 is addressed by llvm-mca.
Flag -print-schedule is mainly used for debugging purposes, and it is only actually used by x86 specific tests. We already have extensive (latency and throughput) tests under "test/tools/llvm-mca" for X86 processor models. That means, most (if not all) existing -print-schedule tests for X86 are redundant.
When flag -print-schedule was first added to LLVM, several files had to be modified; a few APIs gained new arguments (see for example method MCAsmStreamer::EmitInstruction), and MCSubtargetInfo/TargetSubtargetInfo gained a couple of getSchedInfoStr() methods.
Method getSchedInfoStr() had to originally work for both MCInst and MachineInstr. The original implmentation of getSchedInfoStr() introduced a subtle layering violation (reported as PR37160 and then fixed/worked-around by r330615).
In retrospect, that new API could have been designed more optimally. We can always query MCSchedModel to get the latency and throughput. More importantly, the "sched-info" string should not have been generated by the subtarget.
Note, r317782 fixed an issue where "print-schedule" didn't work very well in the presence of inline assembly. That commit is also reverted by this change.
In conclusion: I think that we can safely remove the -print-schedule flag. It was previously very useful despite the above issues because there was no better alternative. Future tests for machine schedulers can use llvm-mca as tool.
Apologies for the large patch; most of the difference is because several tests have been removed. The rest of the diff is a clean-up, and lines have been removed.
I didn't remove the avx512 tests mainly because I am not entirely sure if we have extensive coverage for those in llvm-mca. For now, I have simply regenerated those using update_llc.py (after having removed flag -print-schedule).
Please let me know what you think.
Thanks in advance,