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

[Peter Waller via llvm-commits]

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@@ -962,7 +962,7 @@ void RegisterInfoEmitter::runMCDesc(raw_ostream &OS, CodeGenTarget &Target,
 
   OS << "extern const MCRegisterDesc " << TargetName
      << "RegDesc[] = { // Descriptors\n";
-  OS << "  { " << RegStrings.get("") << ", 0, 0, 0, 0, 0 },\n";
+  OS << "  { " << RegStrings.get("") << ", 0, 0, 0, 0, 0, 0 },\n";
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peterwaller-arm wrote:

It would be the first entry in the array, which is presumably used to make entry '0' a special, invalid register ID. It worked before your update because if you omit entries in a struct initializer, they get zero-initialized.

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