Index: clang/include/clang/Driver/Options.td
===================================================================
--- clang/include/clang/Driver/Options.td
+++ clang/include/clang/Driver/Options.td
@@ -1923,7 +1923,7 @@
   MarshallingInfoFlag<LangOpts<"RoundingMath">>,
   Normalizer<"makeFlagToValueNormalizer(llvm::RoundingMode::Dynamic)">;
 def fno_rounding_math : Flag<["-"], "fno-rounding-math">, Group<f_Group>, Flags<[CC1Option]>;
-def ftrapping_math : Flag<["-"], "ftrapping-math">, Group<f_Group>;
+def ftrapping_math : Flag<["-"], "ftrapping-math">, Group<f_Group>, Flags<[FC1Option]>;
 def fno_trapping_math : Flag<["-"], "fno-trapping-math">, Group<f_Group>;
 def ffp_contract : Joined<["-"], "ffp-contract=">, Group<f_Group>,
   Flags<[CC1Option, FC1Option, FlangOption]>,
Index: clang/lib/Driver/ToolChains/Flang.cpp
===================================================================
--- clang/lib/Driver/ToolChains/Flang.cpp
+++ clang/lib/Driver/ToolChains/Flang.cpp
@@ -90,6 +90,7 @@
   bool AssociativeMath = false;
   bool ReciprocalMath = false;
   bool RoundingFPMath = false;
+  bool TrappingMath = false;
 
   if (const Arg *A = Args.getLastArg(options::OPT_ffp_contract)) {
     const StringRef Val = A->getValue();
@@ -157,6 +158,12 @@
     case options::OPT_fno_rounding_math:
       RoundingFPMath = false;
       break;
+    case options::OPT_ftrapping_math:
+      TrappingMath = true;
+      break;
+    case options::OPT_fno_trapping_math:
+      TrappingMath = false;
+      break;
     }
 
     // If we handled this option claim it
@@ -178,7 +185,7 @@
   if (!SignedZeros)
     CmdArgs.push_back("-fno-signed-zeros");
 
-  if (AssociativeMath && !SignedZeros)
+  if (AssociativeMath && !SignedZeros && !TrappingMath)
     CmdArgs.push_back("-mreassociate");
 
   if (ReciprocalMath)
@@ -186,6 +193,9 @@
 
   if (RoundingFPMath)
     CmdArgs.push_back("-frounding-math");
+
+  if (TrappingMath)
+    CmdArgs.push_back("-ftrapping-math");
 }
 
 void Flang::ConstructJob(Compilation &C, const JobAction &JA,
Index: flang/include/flang/Common/MathOptionsBase.def
===================================================================
--- flang/include/flang/Common/MathOptionsBase.def
+++ flang/include/flang/Common/MathOptionsBase.def
@@ -41,4 +41,7 @@
 /// Do not assume default floating-point rounding behavior
 ENUM_MATHOPT(RoundingMath, unsigned, 1, 0)
 
+/// Tells the compiler whether to assume that floating point operations can trap
+ENUM_MATHOPT(TrappingMath, unsigned, 1, 0)
+
 #undef ENUM_MATHOPT
Index: flang/include/flang/Frontend/LangOptions.def
===================================================================
--- flang/include/flang/Frontend/LangOptions.def
+++ flang/include/flang/Frontend/LangOptions.def
@@ -36,6 +36,8 @@
 LANGOPT(ReciprocalMath, 1, false)
 /// Do not assume default floating-point rounding behavior
 LANGOPT(RoundingMath, 1, false)
+/// Tells the compiler whether to assume that floating point operations can trap
+LANGOPT(TrappingMath, 1, false)
 
 #undef LANGOPT
 #undef ENUM_LANGOPT
Index: flang/lib/Frontend/CompilerInvocation.cpp
===================================================================
--- flang/lib/Frontend/CompilerInvocation.cpp
+++ flang/lib/Frontend/CompilerInvocation.cpp
@@ -741,6 +741,12 @@
     opts.RoundingMath = true;
   }
 
+  if (const llvm::opt::Arg *a =
+          args.getLastArg(clang::driver::options::OPT_ftrapping_math)) {
+    diags.Report(diagUnimplemented) << a->getOption().getName();
+    opts.TrappingMath = true;
+  }
+
   return true;
 }
 
@@ -972,5 +978,6 @@
       .setNoSignedZeros(langOptions.NoSignedZeros)
       .setAssociativeMath(langOptions.AssociativeMath)
       .setReciprocalMath(langOptions.ReciprocalMath)
-      .setRoundingMath(langOptions.RoundingMath);
+      .setRoundingMath(langOptions.RoundingMath)
+      .setTrappingMath(langOptions.TrappingMath);
 }
Index: flang/lib/Optimizer/Builder/FIRBuilder.cpp
===================================================================
--- flang/lib/Optimizer/Builder/FIRBuilder.cpp
+++ flang/lib/Optimizer/Builder/FIRBuilder.cpp
@@ -619,7 +619,7 @@
   if (options.getReciprocalMath()) {
     arithFMF = arithFMF | mlir::arith::FastMathFlags::arcp;
   }
-  // TODO: getRoundingMath()
+  // TODO: getRoundingMath(), getTrappingMath()
   setFastMathFlags(arithFMF);
 }
 
Index: flang/test/Driver/flang_fp_opts.f90
===================================================================
--- flang/test/Driver/flang_fp_opts.f90
+++ flang/test/Driver/flang_fp_opts.f90
@@ -9,6 +9,7 @@
 ! RUN:      -mreassociate \
 ! RUN:      -freciprocal-math \
 ! RUN:      -frounding-math \
+! RUN:      -ftrapping-math \
 ! RUN:      %s 2>&1 | FileCheck %s
 ! CHECK: ffp-contract= is not currently implemented
 ! CHECK: menable-no-infs is not currently implemented
@@ -18,3 +19,4 @@
 ! CHECK: mreassociate is not currently implemented
 ! CHECK: freciprocal-math is not currently implemented
 ! CHECK: frounding-math is not currently implemented
+! CHECK: ftrapping-math is not currently implemented
Index: flang/test/Driver/frontend-forwarding.f90
===================================================================
--- flang/test/Driver/frontend-forwarding.f90
+++ flang/test/Driver/frontend-forwarding.f90
@@ -38,3 +38,10 @@
 ! CHECK: "-fconvert=little-endian"
 ! CHECK: "-fpass-plugin=Bye
 ! CHECK: "-mllvm" "-print-before-all"
+
+! Check -ftrapping-math. This has to be done separately because it prevents
+! -mreassociate from being forwarded
+! RUN: %flang -fsyntax-only -### %s -o %t 2>&1 \
+! RUN:     -ftrapping-math \
+! RUN:   | FileCheck --check-prefix=CHECK-TRAP %s
+! CHECK-TRAP: "-ftrapping-math"