[clang] 686eb0d - [AST] do not error on APFloat invalidOp in default mode

[Sanjay Patel via cfe-commits]

Author: Sanjay Patel
Date: 2020-10-01T13:46:45-04:00
New Revision: 686eb0d8ded9159b090c3ef7b33a422e1f05166e

URL: https://github.com/llvm/llvm-project/commit/686eb0d8ded9159b090c3ef7b33a422e1f05166e
DIFF: https://github.com/llvm/llvm-project/commit/686eb0d8ded9159b090c3ef7b33a422e1f05166e.diff

LOG: [AST] do not error on APFloat invalidOp in default mode

If FP exceptions are ignored, we should not error out of compilation
just because APFloat indicated an exception.
This is required as a preliminary step for D88238
which changes APFloat behavior for signaling NaN convert() to set
the opInvalidOp exception status.

Currently, there is no way to trigger this error because convert()
never sets opInvalidOp. FP binops that set opInvalidOp also create
a NaN, so the path to checkFloatingPointResult() is blocked by a
different diagnostic:

  // [expr.pre]p4:
  //   If during the evaluation of an expression, the result is not
  //   mathematically defined [...], the behavior is undefined.
  // FIXME: C++ rules require us to not conform to IEEE 754 here.
  if (LHS.isNaN()) {
    Info.CCEDiag(E, diag::note_constexpr_float_arithmetic) << LHS.isNaN();
    return Info.noteUndefinedBehavior();
  }
  return checkFloatingPointResult(Info, E, St);

Differential Revision: https://reviews.llvm.org/D88664

Added: 
    

Modified: 
    clang/lib/AST/ExprConstant.cpp

Removed: 
    


################################################################################
diff  --git a/clang/lib/AST/ExprConstant.cpp b/clang/lib/AST/ExprConstant.cpp
index b17eed2dc823..4460e3a17e6d 100644
--- a/clang/lib/AST/ExprConstant.cpp
+++ b/clang/lib/AST/ExprConstant.cpp
@@ -2439,7 +2439,8 @@ static bool checkFloatingPointResult(EvalInfo &Info, const Expr *E,
     return false;
   }
 
-  if (St & APFloat::opStatus::opInvalidOp) {
+  if ((St & APFloat::opStatus::opInvalidOp) &&
+      FPO.getFPExceptionMode() != LangOptions::FPE_Ignore) {
     // There is no usefully definable result.
     Info.FFDiag(E);
     return false;