[PATCH] D151587: [clang][ConstantEmitter] have tryEmitPrivate[ForVarInit] try ConstExprEmitter fast-path first

[Eli Friedman via Phabricator via cfe-commits]

efriedma added inline comments.


================
Comment at: clang/lib/AST/ExprConstant.cpp:8360
+  // Do not constant fold an R-value.
+  if (Info.EvalMode == EvalInfo::EM_ConstantFold && !E->isLValue())
+    return false;
----------------
Checking isLValue() doesn't make sense; consider:

```
struct R { mutable long x; };
struct Z { const R &x, y; };
Z z = { R{1}, z.x.x=10 };
```

Maybe also want to check for EM_IgnoreSideEffects?  Not sure what cases, if any, that would affect.

We should probably check `E->getStorageDuration() == SD_Static`.  The cases where it's a local temporary don't hit the getOrCreateValue() codepath, so the evaluated value should be handled correctly.

Checking EvalMode feels a little weird, but I guess it should do the right thing in the cases I can think of?  I'd like a second opinion on this.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D151587/new/

https://reviews.llvm.org/D151587