[llvm] [WIP][RFC] Teach MCA constant registers do not create dependencies (PR #89387)

[Rin Dobrescu via llvm-commits]

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@@ -977,7 +977,8 @@ void RegisterInfoEmitter::runMCDesc(raw_ostream &OS, CodeGenTarget &Target,
        << DiffSeqs.get(SubRegLists[i]) << ", " << DiffSeqs.get(SuperRegLists[i])
        << ", " << SubRegIdxSeqs.get(SubRegIdxLists[i]) << ", "
        << (Offset << RegUnitBits | FirstRU) << ", "
-       << LaneMaskSeqs.get(RegUnitLaneMasks[i]) << " },\n";
+       << LaneMaskSeqs.get(RegUnitLaneMasks[i]) << ", " << Reg.Constant
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Rin18 wrote:

Thanks for pointing this out. I took a look at the TableGen tests relating to `RegisterInfoEmitter.cpp`. The tests I found were only related to register cost values, so this change shouldn't affect them. 

https://github.com/llvm/llvm-project/pull/89387