================
@@ -2268,13 +2293,22 @@ CodeGenFunction::EmitNullInitialization(Address
DestPtr, QualType Ty) {
// Get and call the appropriate llvm.memcpy overload.
Builder.CreateMemCpy(DestPtr, SrcPtr, SizeVal, false);
- return;
+ } else {
+ // Otherwise, just memset the whole thing to zero. This is legal
----------------
ojhunt wrote:
This means types that require constructors will be doing zero initialization,
then reinitializing fields. From a codegen PoV this can lead to codegen along
the lines of
```
zero the memory; // compiler is set to initialize all memory
zero the memory; // this branch means objects that are not zero initializable
get initialized again
initialize the memory; // the struct is not zero initializable the
constructor/initializer will run
```
Ideally the compiler will optimized this down, but it's both extra codegen, and
extra optimization work.
Given that your model assumes that null is a safe value for PFP fields, the
`isZeroInitializable()` call should return true. For non-zero initializable
objects, the initialization code for the object is responsible for initializing
the PFP fields.
https://github.com/llvm/llvm-project/pull/133538
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