[flang] Add -f[no-]approx-func

[tblah]

Summary

Only add the option processing and store the result. No attributes are added to FIR yet.

[kiranchandramohan]

LGTM.

clang/include/clang/Driver/Options.td

 def fassociative_math : Flag<["-"], "fassociative-math">, Group<f_Group>;
 def fno_associative_math : Flag<["-"], "fno-associative-math">, Group<f_Group>;
 defm reciprocal_math : BoolFOption<"reciprocal-math",
   LangOpts<"AllowRecip">, DefaultFalse,
   PosFlag<SetTrue, [CC1Option], "Allow division operations to be reassociated",
           [funsafe_math_optimizations.KeyPath]>,
   NegFlag<SetFalse>>;
 defm approx_func : BoolFOption<"approx-func", LangOpts<"ApproxFunc">, DefaultFalse,
-   PosFlag<SetTrue, [CC1Option], "Allow certain math function calls to be replaced "
+   PosFlag<SetTrue, [CC1Option, FC1Option, FlangOption], "Allow certain math function calls to be replaced "
            "with an approximately equivalent calculation",
            [funsafe_math_optimizations.KeyPath]>,
    NegFlag<SetFalse>>;
 defm finite_math_only : BoolFOption<"finite-math-only",
   LangOpts<"FiniteMathOnly">, DefaultFalse,
   PosFlag<SetTrue, [CC1Option], "", [cl_finite_math_only.KeyPath, ffast_math.KeyPath]>,
   NegFlag<SetFalse>>;
 defm signed_zeros : BoolFOption<"signed-zeros",

clang/lib/Driver/ToolChains/Flang.cpp

void Flang::AddPicOptions(const ArgList &Args, ArgStringList &CmdArgs) const {
   }
 }
 
 static void addFloatingPointOptions(const Driver &D, const ArgList &Args,
                                     ArgStringList &CmdArgs) {
   StringRef FPContract;
   bool HonorINFs = true;
   bool HonorNaNs = true;
+  bool ApproxFunc = false;
 
   if (const Arg *A = Args.getLastArg(options::OPT_ffp_contract)) {
     const StringRef Val = A->getValue();
     if (Val == "fast" || Val == "off") {
       FPContract = Val;
     } else if (Val == "on") {
       // Warn instead of error because users might have makefiles written for
       // gfortran (which accepts -ffp-contract=on)
case options::OPT_fno_honor_infinities:
       HonorINFs = false;
       break;
     case options::OPT_fhonor_nans:
       HonorNaNs = true;
       break;
     case options::OPT_fno_honor_nans:
       HonorNaNs = false;
       break;
+    case options::OPT_fapprox_func:
+      ApproxFunc = true;
+      break;
+    case options::OPT_fno_approx_func:
+      ApproxFunc = false;
+      break;
     }
 
     // If we handled this option claim it
     A->claim();
   }
 
   if (!FPContract.empty())
     CmdArgs.push_back(Args.MakeArgString("-ffp-contract=" + FPContract));
 
   if (!HonorINFs)
     CmdArgs.push_back("-menable-no-infs");
 
   if (!HonorNaNs)
     CmdArgs.push_back("-menable-no-nans");
+
+  if (ApproxFunc)
+    CmdArgs.push_back("-fapprox-func");
 }
 
 void Flang::ConstructJob(Compilation &C, const JobAction &JA,
                          const InputInfo &Output, const InputInfoList &Inputs,
                          const ArgList &Args, const char *LinkingOutput) const {
   const auto &TC = getToolChain();
   const llvm::Triple &Triple = TC.getEffectiveTriple();
   const std::string &TripleStr = Triple.getTriple();

flang/include/flang/Frontend/LangOptions.def

 #endif
 
 ENUM_LANGOPT(FPContractMode, FPModeKind, 2, FPM_Off) ///< FP Contract Mode (off/fast)
 
 /// Permit floating point optimization without regard to infinities
 LANGOPT(NoHonorInfs, 1, false)
 /// Permit floating point optimization without regard to NaN
 LANGOPT(NoHonorNaNs, 1, false)
+/// Allow math functions to be replaced with an approximately equivalent calculation
+LANGOPT(ApproxFunc, 1, false)
 
 #undef LANGOPT
 #undef ENUM_LANGOPT

flang/lib/Frontend/CompilerInvocation.cpp

static bool parseFloatingPointArgs(CompilerInvocation &invoc,
   }
 
   if (const llvm::opt::Arg *a =
           args.getLastArg(clang::driver::options::OPT_menable_no_nans)) {
     diags.Report(diagUnimplemented) << a->getOption().getName();
     opts.NoHonorNaNs = true;
   }
 
+  if (const llvm::opt::Arg *a =
+          args.getLastArg(clang::driver::options::OPT_fapprox_func)) {
+    diags.Report(diagUnimplemented) << a->getOption().getName();
+    opts.ApproxFunc = true;
+  }
+
   return true;
 }
 
 bool CompilerInvocation::createFromArgs(
     CompilerInvocation &res, llvm::ArrayRef<const char *> commandLineArgs,
     clang::DiagnosticsEngine &diags) {
 
   bool success = true;

flang/test/Driver/driver-help-hidden.f90

 ! CHECK-NEXT: -###      Print (but do not run) the commands to run for this compilation
 ! CHECK-NEXT: -cpp      Enable predefined and command line preprocessor macros
 ! CHECK-NEXT: -c        Only run preprocess, compile, and assemble steps
 ! CHECK-NEXT: -D <macro>=<value>     Define <macro> to <value> (or 1 if <value> omitted)
 ! CHECK-NEXT: -emit-llvm             Use the LLVM representation for assembler and object files
 ! CHECK-NEXT: -E        Only run the preprocessor
 ! CHECK-NEXT: -falternative-parameter-statement
 ! CHECK-NEXT: Enable the old style PARAMETER statement
+! CHECK-NEXT: -fapprox-func          Allow certain math function calls to be replaced with an approximately equivalent calculation
 ! CHECK-NEXT: -fbackslash            Specify that backslash in string introduces an escape character
 ! CHECK-NEXT: -fcolor-diagnostics    Enable colors in diagnostics
 ! CHECK-NEXT: -fconvert=<value>      Set endian conversion of data for unformatted files
 ! CHECK-NEXT: -fdefault-double-8     Set the default double precision kind to an 8 byte wide type
 ! CHECK-NEXT: -fdefault-integer-8    Set the default integer kind to an 8 byte wide type
 ! CHECK-NEXT: -fdefault-real-8       Set the default real kind to an 8 byte wide type
 ! CHECK-NEXT: -ffixed-form           Process source files in fixed form
 ! CHECK-NEXT: -ffixed-line-length=<value>

flang/test/Driver/driver-help.f90

 ! HELP-NEXT: -###                   Print (but do not run) the commands to run for this compilation
 ! HELP-NEXT: -cpp                   Enable predefined and command line preprocessor macros
 ! HELP-NEXT: -c                     Only run preprocess, compile, and assemble steps
 ! HELP-NEXT: -D <macro>=<value>     Define <macro> to <value> (or 1 if <value> omitted)
 ! HELP-NEXT: -emit-llvm             Use the LLVM representation for assembler and object files
 ! HELP-NEXT: -E                     Only run the preprocessor
 ! HELP-NEXT: -falternative-parameter-statement
 ! HELP-NEXT: Enable the old style PARAMETER statement
+! HELP-NEXT: -fapprox-func          Allow certain math function calls to be replaced with an approximately equivalent calculation
 ! HELP-NEXT: -fbackslash            Specify that backslash in string introduces an escape character
 ! HELP-NEXT: -fcolor-diagnostics    Enable colors in diagnostics
 ! HELP-NEXT: -fconvert=<value>      Set endian conversion of data for unformatted files
 ! HELP-NEXT: -fdefault-double-8     Set the default double precision kind to an 8 byte wide type
 ! HELP-NEXT: -fdefault-integer-8    Set the default integer kind to an 8 byte wide type
 ! HELP-NEXT: -fdefault-real-8       Set the default real kind to an 8 byte wide type
 ! HELP-NEXT: -ffixed-form           Process source files in fixed form
 ! HELP-NEXT: -ffixed-line-length=<value>

 ! HELP-FC1-NEXT: -D <macro>=<value>     Define <macro> to <value> (or 1 if <value> omitted)
 ! HELP-FC1-NEXT: -emit-llvm-bc          Build ASTs then convert to LLVM, emit .bc file
 ! HELP-FC1-NEXT: -emit-llvm Use the LLVM representation for assembler and object files
 ! HELP-FC1-NEXT: -emit-mlir Build the parse tree, then lower it to MLIR
 ! HELP-FC1-NEXT: -emit-obj Emit native object files
 ! HELP-FC1-NEXT: -E                     Only run the preprocessor
 ! HELP-FC1-NEXT: -falternative-parameter-statement
 ! HELP-FC1-NEXT: Enable the old style PARAMETER statement
+! HELP-FC1-NEXT: -fapprox-func          Allow certain math function calls to be replaced with an approximately equivalent calculation
 ! HELP-FC1-NEXT: -fbackslash            Specify that backslash in string introduces an escape character
 ! HELP-FC1-NEXT: -fcolor-diagnostics     Enable colors in diagnostics
 ! HELP-FC1-NEXT: -fconvert=<value>      Set endian conversion of data for unformatted files
 ! HELP-FC1-NEXT: -fdebug-dump-all       Dump symbols and the parse tree after the semantic checks
 ! HELP-FC1-NEXT: -fdebug-dump-parse-tree-no-sema
 ! HELP-FC1-NEXT:                        Dump the parse tree (skips the semantic checks)
 ! HELP-FC1-NEXT: -fdebug-dump-parse-tree Dump the parse tree
 ! HELP-FC1-NEXT: -fdebug-dump-parsing-log

flang/test/Driver/flang_fp_opts.f90

 ! Test for handling of floating point options within the frontend driver
 
 ! RUN: %flang_fc1 \
 ! RUN:      -ffp-contract=fast \
 ! RUN:      -menable-no-infs \
 ! RUN:      -menable-no-nans \
+! RUN:      -fapprox-func \
 ! RUN:      %s 2>&1 | FileCheck %s
 ! CHECK: ffp-contract= is not currently implemented
 ! CHECK: menable-no-infs is not currently implemented
 ! CHECK: menable-no-nans is not currently implemented
+! CHECK: fapprox-func is not currently implemented

flang/test/Driver/frontend-forwarding.f90

 ! Test that flang-new forwards Flang frontend
 ! options to flang-new -fc1 as expected.
 
 ! RUN: %flang -fsyntax-only -### %s -o %t 2>&1 \
 ! RUN:     -finput-charset=utf-8 \
 ! RUN:     -fdefault-double-8 \
 ! RUN:     -fdefault-integer-8 \
 ! RUN:     -fdefault-real-8 \
 ! RUN:     -flarge-sizes \
 ! RUN:     -fconvert=little-endian \
 ! RUN:     -ffp-contract=fast \
 ! RUN:     -fno-honor-infinities \
 ! RUN:     -fno-honor-nans \
+! RUN:     -fapprox-func \
 ! RUN:     -mllvm -print-before-all\
 ! RUN:     -P \
 ! RUN:   | FileCheck %s
 
 ! CHECK: "-P"
 ! CHECK: "-finput-charset=utf-8"
 ! CHECK: "-fdefault-double-8"
 ! CHECK: "-fdefault-integer-8"
 ! CHECK: "-fdefault-real-8"
 ! CHECK: "-flarge-sizes"
 ! CHECK: "-ffp-contract=fast"
 ! CHECK: "-menable-no-infs"
 ! CHECK: "-menable-no-nans"
+! CHECK: "-fapprox-func"
 ! CHECK: "-fconvert=little-endian"
 ! CHECK:  "-mllvm" "-print-before-all"