[clang] [clang] Add size filter for stack auto init (PR #74777)

[Eli Friedman via cfe-commits]

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@@ -1759,20 +1759,29 @@ void CodeGenFunction::emitZeroOrPatternForAutoVarInit(QualType type,
                                                       const VarDecl &D,
                                                       Address Loc) {
   auto trivialAutoVarInit = getContext().getLangOpts().getTrivialAutoVarInit();
+  auto trivialAutoVarInitSizeBound =
+      getContext().getLangOpts().TrivialAutoVarInitSizeBound;
   CharUnits Size = getContext().getTypeSizeInChars(type);
   bool isVolatile = type.isVolatileQualified();
   if (!Size.isZero()) {
+    auto allocSize = CGM.getDataLayout().getTypeAllocSize(Loc.getElementType());
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efriedma-quic wrote:

Ignoring a few less common cases (C++ classes with non-trivial constructors, unions, self-referencing initializers), variable initialization is generally is an all-or-nothing proposition. If you write something like `struct X { int x,y,z; }; struct X x[100] = {0};`, that initializes every field of every element.  What examples are you worried about?

https://github.com/llvm/llvm-project/pull/74777