Fix option handling in driver

Author: mjklemm

clang/lib/Driver/ToolChains/Flang.cpp

@@ -822,10 +822,15 @@ static void addFloatingPointOptions(const Driver &D, const ArgList &Args,
                                          complexRangeKindToStr(Range)));
   }
 
-  if (Args.hasArg(options::OPT_ffast_real_mod))
-    CmdArgs.push_back("-ffast-real-mod");
-  if (Args.hasArg(options::OPT_fno_fast_real_mod))
-    CmdArgs.push_back("-fno-fast-real-mod");
+  if (llvm::opt::Arg *A =
+          Args.getLastArg(clang::options::OPT_ffast_real_mod,
+                          clang::options::OPT_fno_fast_real_mod)) {
+    if (A->getOption().matches(clang::options::OPT_ffast_real_mod))
+      CmdArgs.push_back("-ffast-real-mod");
+    else if (A->getOption().matches(
+                 clang::options::OPT_fno_fast_real_mod))
+      CmdArgs.push_back("-fno-fast-real-mod");
+  }
 
   if (!HonorINFs && !HonorNaNs && AssociativeMath && ReciprocalMath &&
       ApproxFunc && !SignedZeros &&

flang/test/Driver/fast-real-mod.f90

@@ -1,8 +1,12 @@
 ! RUN: %flang -ffast-real-mod -### -c %s 2>&1 | FileCheck %s -check-prefix CHECK-FAST-REAL-MOD
 ! RUN: %flang -fno-fast-real-mod -### -c %s 2>&1 | FileCheck %s -check-prefix CHECK-NO-FAST-REAL-MOD
+! RUN: %flang -fno-fast-real-mod -ffast-real-mod -### -c %s 2>&1 | FileCheck %s -check-prefix CHECK-FAST-REAL-MOD
+! RUN: %flang -ffast-real-mod -fno-fast-real-mod -### -c %s 2>&1 | FileCheck %s -check-prefix CHECK-NO-FAST-REAL-MOD
 
 ! CHECK-FAST-REAL-MOD: "-ffast-real-mod"
+! CHECK-FAST-REAL-MOD-NOT: "-fno-fast-real-mod"
 ! CHECK-NO-FAST-REAL-MOD: "-fno-fast-real-mod"
+! CHECK-NO-FAST-REAL-MOD-NOT: "-fast-real-mod"
 
 program test
     ! nothing to be done in here