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

[Justin Stitt 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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JustinStitt wrote:

I emailed @nikic for access to his tool.

AFAICT, the cost here is a linear AST scan -- which should be pretty minimal (reminder to others, this already runs for optimized builds due to `shouldEmitLifetimeMarkers()`).

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