[clang] [Clang] Initialize bypassed variables w/ trivial-auto-var-init (PR #181937)

[Nick Desaulniers via cfe-commits]

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@@ -59,13 +63,27 @@ class VarBypassDetector {
     return AlwaysBypassed || Bypasses.contains(D);
   }
 
+  /// Returns true if jump sources cannot be determined (e.g. computed gotos),
+  /// so all variables must be treated as bypassed.
+  bool isAlwaysBypassed() const { return AlwaysBypassed; }
+
+  /// Returns the variables bypassed by jumps from the given source statement,
+  /// or nullptr if it bypasses none.
+  const llvm::DenseSet<const VarDecl *> *
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nickdesaulniers wrote:

"Optimization Fuel"

A semi formal term for helping you find bugs exposed by (possibly bad) compiler transforms.  Say blanked enable -ftrivial-auto-var-init=zero and your code starts crashing. Why? How? WTF?  Well, if TAVI default initializes say 1000 variables, then -ftrivial-auto-var-init-stop-after= gives you a flag to start with a value of 500, and start bisecting.  Then ideally from there you can figure out which specific case is giving you a problem, which should then help you disambiguate between compiler bug vs issue in source.

I don't even get any relevant search engine hits for "optimization fuel" above the fold...

https://github.com/llvm/llvm-project/pull/181937