[llvm-bugs] [Bug 37602] New: [llvm-exegesis] Ignore unsupported instructions via UnsupportedFeatures

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=37602

            Bug ID: 37602
           Summary: [llvm-exegesis] Ignore unsupported instructions via
                    UnsupportedFeatures
           Product: new-bugs
           Version: unspecified
          Hardware: PC
                OS: Windows NT
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: new bugs
          Assignee: unassignedbugs at nondot.org
          Reporter: llvm-dev at redking.me.uk
                CC: andrea.dibiagio at gmail.com, clement.courbet at gmail.com,
                    craig.topper at gmail.com, gchatelet at google.com,
                    llvm-bugs at lists.llvm.org, spatel+llvm at rotateright.com
        Depends on: 37601
            Blocks: 32325

Using the script detailed in
http://llvm.org/docs/CommandGuide/llvm-exegesis.html is very slow as we end up
testing instructions that we know aren't supported on the CPU, but we still
have to wait for the JIT to fail to move on.

It would be better if:

(a) llvm-exegesis made use of the scheduler model's UnsupportedFeatures field
to test if the instruction is supported and if not, early out. In particular
this would help considerably with older CPUs that don't support all the AVX512
instructions......

(b) the models made use of the UnsupportedFeatures field to ignore ISAs that it
doesn't support see [Bug #37601] - for SandyBridge/Haswell where we need to
"support" additional ISAs we could at least hack the field locally to match the
test CPU.


Referenced Bugs:

https://bugs.llvm.org/show_bug.cgi?id=32325
[Bug 32325] [META][X86] Improve implementation and use of X86 scheduler models
https://bugs.llvm.org/show_bug.cgi?id=37601
[Bug 37601] [X86] Scheduler models should use UnsupportedFeatures to indicate
unsupported ISAs
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