[PATCH] D52839: Inform AST's UnaryOperator of FENV_ACCESS

[Richard Smith - zygoloid via Phabricator via cfe-commits]

rsmith added a comment.

Maybe take this very slightly further so it becomes testable: change the expression evaluator (lib/AST/ExprConstant.cpp) so it treats floating-point operations as non-constant if they're potentially-overflowing.

You also need to update lib/Serialization/AST{Reader,Writer}Stmt.cpp to round-trip this information through AST files.

How do you intend for this to work in template instantiation? Do we record the pragmas in the AST (and likewise for the state on entry to each function) so that we can rebuild the `FPOptions` during instantiation, or should we be inheriting the `FPOptions` from the expression in the template onto the expression in the instantiation? In the latter case, it would make more sense to me to track `FPOptions` on the `Scope` rather than as a `Sema` member, so that the state is more-obviously unavailable during template instantiation.



================
Comment at: include/clang/AST/Expr.h:1794-1796
+  // This is only meaningful for operations on floating point types and 0
+  // otherwise.
+  unsigned FPFeatures : 3;
----------------
Move this adjacent to the other bitfields so we don't spend 32 / 64 bits on it.


Repository:
  rC Clang

https://reviews.llvm.org/D52839