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

[Eli Friedman via cfe-commits]

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@@ -1544,8 +1544,12 @@ void CodeGenFunction::GenerateCode(GlobalDecl GD, llvm::Function *Fn,
       ShouldEmitLifetimeMarkers = true;
 
     // Initialize helper which will detect jumps which can cause invalid
-    // lifetime markers.
-    if (ShouldEmitLifetimeMarkers)
+    // lifetime markers or bypass trivial auto var init.
+    bool NeedsBypassDetection =
+        ShouldEmitLifetimeMarkers ||
+        (CGM.getLangOpts().getTrivialAutoVarInit() !=
+         LangOptions::TrivialAutoVarInitKind::Uninitialized);
+    if (NeedsBypassDetection)
       Bypasses.Init(CGM, Body);
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efriedma-quic wrote:

That's what I was afraid of.

If we have to take some penalty, I guess I'm okay with that, but I'd appreciate if you can investigate a bit.  Is there some way we can reduce the amount of work VarBypassDetector does?  Maybe have Sema set a flag if it sees certain constructs?

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