================
@@ -2901,34 +2907,43 @@ class CallExpr : public Expr {
//
// * An optional of type FPOptionsOverride.
//
- // Note that we store the offset in bytes from the this pointer to the start
- // of the trailing objects. It would be perfectly possible to compute it
- // based on the dynamic kind of the CallExpr. However 1.) we have plenty of
- // space in the bit-fields of Stmt. 2.) It was benchmarked to be faster to
- // compute this once and then load the offset from the bit-fields of Stmt,
- // instead of re-computing the offset each time the trailing objects are
- // accessed.
+ // CallExpr subclasses are asssumed to be 32 bytes or less, and CallExpr
+ // itself is 24 bytes. To avoid having to recompute or store the offset of
the
+ // trailing objects, we put it at 32 bytes (such that it is suitable for all
+ // subclasses) We use the 8 bytes gap left for instances of CallExpr to store
+ // the begin source location, which has a significant impact on perf as
+ // getBeginLoc is assumed to be cheap.
+ // The layourt is as follow:
+ // CallExpr | Begin | 4 bytes left | Trailing Objects
+ // CXXMemberCallExpr | Trailing Objects
+ // A bit in CallExprBitfields indicates if source locations are presents.
----------------
tbaederr wrote:
```suggestion
// A bit in CallExprBitfields indicates if source locations are present.
```
https://github.com/llvm/llvm-project/pull/141058
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