[flang] Add -ffp-contract option processing

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

Only the "off" and "fast" options are supported. "fast-honor-pragmas" is not applicable because we do not implement `#pragma clang fp contract()` in Fortran [1]. "on" is not supported because it is unclear how to fuse only within individual statements. gfortran also does not implement "on": treating it as an "off".

Currently the default value is "off" to preserve existing behavior. gfortran uses "fast" by default and that may be the right thing for flang-new after further discussion in the future, but that can be changed separately. gfortran's documentation is available [[ https://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html | here ]].

[1] https://clang.llvm.org/docs/LanguageExtensions.html#extensions-to-specify-floating-point-flags

Reviewed By: vzakhari, awarzynski

Differential Revision: https://reviews.llvm.org/D136080

11 files changed, 167 insertions, 1 deletions

diff --git a/flang/include/flang/Frontend/CompilerInvocation.h b/flang/include/flang/Frontend/CompilerInvocation.h
index 3a6dafa301d3..a5895451bb74 100644
--- a/flang/include/flang/Frontend/CompilerInvocation.h
+++ b/flang/include/flang/Frontend/CompilerInvocation.h
@@ -15,6 +15,7 @@
 
 #include "flang/Frontend/CodeGenOptions.h"
 #include "flang/Frontend/FrontendOptions.h"
+#include "flang/Frontend/LangOptions.h"
 #include "flang/Frontend/PreprocessorOptions.h"
 #include "flang/Frontend/TargetOptions.h"
 #include "flang/Lower/LoweringOptions.h"
@@ -78,6 +79,9 @@ class CompilerInvocation : public CompilerInvocationBase {
   /// Options controlling IRgen and the backend.
   Fortran::frontend::CodeGenOptions codeGenOpts;
 
+  /// Options controlling language dialect.
+  Fortran::frontend::LangOptions langOpts;
+
   // Semantics context
   std::unique_ptr<Fortran::semantics::SemanticsContext> semanticsContext;
 
@@ -140,6 +144,9 @@ public:
   CodeGenOptions &getCodeGenOpts() { return codeGenOpts; }
   const CodeGenOptions &getCodeGenOpts() const { return codeGenOpts; }
 
+  LangOptions &getLangOpts() { return langOpts; }
+  const LangOptions &getLangOpts() const { return langOpts; }
+
   Fortran::lower::LoweringOptions &getLoweringOpts() { return loweringOpts; }
   const Fortran::lower::LoweringOptions &getLoweringOpts() const {
     return loweringOpts;
diff --git a/flang/include/flang/Frontend/LangOptions.def b/flang/include/flang/Frontend/LangOptions.def
new file mode 100644
index 000000000000..c4d0ec5329b2
--- /dev/null
+++ b/flang/include/flang/Frontend/LangOptions.def
@@ -0,0 +1,25 @@
+//===------ LangOptions.def - Code generation option database ----- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines the language dialect options. Users of this file
+// must define the LANGOPT macro to make use of this information.
+//
+//===----------------------------------------------------------------------===//
+#ifndef LANGOPT
+#  error Define the LANGOPT macro to handle language options
+#endif
+
+#ifndef ENUM_LANGOPT
+#  define ENUM_LANGOPT(Name, Type, Bits, Default) \
+LANGOPT(Name, Bits, Default)
+#endif
+
+ENUM_LANGOPT(FPContractMode, FPModeKind, 2, FPM_Off) ///< FP Contract Mode (off/fast)
+
+#undef LANGOPT
+#undef ENUM_LANGOPT
diff --git a/flang/include/flang/Frontend/LangOptions.h b/flang/include/flang/Frontend/LangOptions.h
new file mode 100644
index 000000000000..c8edbfdbc8d1
--- /dev/null
+++ b/flang/include/flang/Frontend/LangOptions.h
@@ -0,0 +1,60 @@
+//===------ LangOptions.h ---------------------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+//  This file defines the LangOptions interface, which holds the
+//  configuration for LLVM's middle-end and back-end. It controls LLVM's code
+//  generation into assembly or machine code.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_FLANG_FRONTEND_LANGOPTIONS_H
+#define LLVM_FLANG_FRONTEND_LANGOPTIONS_H
+
+namespace Fortran::frontend {
+
+/// Bitfields of LangOptions, split out from LangOptions to ensure
+/// that this large collection of bitfields is a trivial class type.
+class LangOptionsBase {
+
+public:
+  enum FPModeKind {
+    // Do not fuse FP ops
+    FPM_Off,
+
+    // Aggressively fuse FP ops (E.g. FMA).
+    FPM_Fast,
+  };
+
+#define LANGOPT(Name, Bits, Default) unsigned Name : Bits;
+#define ENUM_LANGOPT(Name, Type, Bits, Default)
+#include "flang/Frontend/LangOptions.def"
+
+protected:
+#define LANGOPT(Name, Bits, Default)
+#define ENUM_LANGOPT(Name, Type, Bits, Default) unsigned Name : Bits;
+#include "flang/Frontend/LangOptions.def"
+};
+
+/// Tracks various options which control the dialect of Fortran that is
+/// accepted. Based on clang::LangOptions
+class LangOptions : public LangOptionsBase {
+
+public:
+  // Define accessors/mutators for code generation options of enumeration type.
+#define LANGOPT(Name, Bits, Default)
+#define ENUM_LANGOPT(Name, Type, Bits, Default)                                \
+  Type get##Name() const { return static_cast<Type>(Name); }                   \
+  void set##Name(Type Value) { Name = static_cast<unsigned>(Value); }
+#include "flang/Frontend/LangOptions.def"
+
+  LangOptions();
+};
+
+} // end namespace Fortran::frontend
+
+#endif
diff --git a/flang/lib/Frontend/CMakeLists.txt b/flang/lib/Frontend/CMakeLists.txt
index 45fc97867e18..4abca70acaba 100644
--- a/flang/lib/Frontend/CMakeLists.txt
+++ b/flang/lib/Frontend/CMakeLists.txt
@@ -7,6 +7,7 @@ add_flang_library(flangFrontend
   FrontendAction.cpp
   FrontendActions.cpp
   FrontendOptions.cpp
+  LangOptions.cpp
   TextDiagnosticPrinter.cpp
   TextDiagnosticBuffer.cpp
   TextDiagnostic.cpp
diff --git a/flang/lib/Frontend/CompilerInvocation.cpp b/flang/lib/Frontend/CompilerInvocation.cpp
index 761300b807cc..3a64086be33d 100644
--- a/flang/lib/Frontend/CompilerInvocation.cpp
+++ b/flang/lib/Frontend/CompilerInvocation.cpp
@@ -658,6 +658,42 @@ static bool parseDialectArgs(CompilerInvocation &res, llvm::opt::ArgList &args,
   return diags.getNumErrors() == numErrorsBefore;
 }
 
+/// Parses all floating point related arguments and populates the
+/// CompilerInvocation accordingly.
+/// Returns false if new errors are generated.
+///
+/// \param [out] invoc Stores the processed arguments
+/// \param [in] args The compiler invocation arguments to parse
+/// \param [out] diags DiagnosticsEngine to report erros with
+static bool parseFloatingPointArgs(CompilerInvocation &invoc,
+                                   llvm::opt::ArgList &args,
+                                   clang::DiagnosticsEngine &diags) {
+  LangOptions &opts = invoc.getLangOpts();
+  const unsigned diagUnimplemented = diags.getCustomDiagID(
+      clang::DiagnosticsEngine::Warning, "%0 is not currently implemented");
+
+  if (const llvm::opt::Arg *a =
+          args.getLastArg(clang::driver::options::OPT_ffp_contract)) {
+    const llvm::StringRef val = a->getValue();
+    enum LangOptions::FPModeKind fpContractMode;
+
+    if (val == "off")
+      fpContractMode = LangOptions::FPM_Off;
+    else if (val == "fast")
+      fpContractMode = LangOptions::FPM_Fast;
+    else {
+      diags.Report(clang::diag::err_drv_unsupported_option_argument)
+          << a->getOption().getName() << val;
+      return false;
+    }
+
+    diags.Report(diagUnimplemented) << a->getOption().getName();
+    opts.setFPContractMode(fpContractMode);
+  }
+
+  return true;
+}
+
 bool CompilerInvocation::createFromArgs(
     CompilerInvocation &res, llvm::ArrayRef<const char *> commandLineArgs,
     clang::DiagnosticsEngine &diags) {
@@ -712,6 +748,8 @@ bool CompilerInvocation::createFromArgs(
   res.frontendOpts.mlirArgs =
       args.getAllArgValues(clang::driver::options::OPT_mmlir);
 
+  success &= parseFloatingPointArgs(res, args, diags);
+
   return success;
 }
 
diff --git a/flang/lib/Frontend/LangOptions.cpp b/flang/lib/Frontend/LangOptions.cpp
new file mode 100644
index 000000000000..a08cb363384c
--- /dev/null
+++ b/flang/lib/Frontend/LangOptions.cpp
@@ -0,0 +1,24 @@
+//===------ LangOptions.cpp -----------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// Coding style: https://mlir.llvm.org/getting_started/DeveloperGuide/
+//
+//===----------------------------------------------------------------------===//
+
+#include "flang/Frontend/LangOptions.h"
+#include <string.h>
+
+namespace Fortran::frontend {
+
+LangOptions::LangOptions() {
+#define LANGOPT(Name, Bits, Default) Name = Default;
+#define ENUM_LANGOPT(Name, Type, Bits, Default) set##Name(Default);
+#include "flang/Frontend/LangOptions.def"
+}
+
+} // end namespace Fortran::frontend
diff --git a/flang/test/Driver/driver-help-hidden.f90 b/flang/test/Driver/driver-help-hidden.f90
index e6309bb9fd6d..d2dc82ea1b52 100644
--- a/flang/test/Driver/driver-help-hidden.f90
+++ b/flang/test/Driver/driver-help-hidden.f90
@@ -31,6 +31,7 @@
 ! CHECK-NEXT: -ffixed-form           Process source files in fixed form
 ! CHECK-NEXT: -ffixed-line-length=<value>
 ! CHECK-NEXT: Use <value> as character line width in fixed mode
+! CHECK-NEXT: -ffp-contract=<value> Form fused FP ops (e.g. FMAs)
 ! CHECK-NEXT: -ffree-form            Process source files in free form
 ! CHECK-NEXT: -fimplicit-none        No implicit typing allowed unless overridden by IMPLICIT statements
 ! CHECK-NEXT: -finput-charset=<value> Specify the default character set for source files
diff --git a/flang/test/Driver/driver-help.f90 b/flang/test/Driver/driver-help.f90
index daddd254b618..3ab509c7129e 100644
--- a/flang/test/Driver/driver-help.f90
+++ b/flang/test/Driver/driver-help.f90
@@ -31,6 +31,7 @@
 ! HELP-NEXT: -ffixed-form           Process source files in fixed form
 ! HELP-NEXT: -ffixed-line-length=<value>
 ! HELP-NEXT: Use <value> as character line width in fixed mode
+! HELP-NEXT: -ffp-contract=<value> Form fused FP ops (e.g. FMAs)
 ! HELP-NEXT: -ffree-form            Process source files in free form
 ! HELP-NEXT: -fimplicit-none        No implicit typing allowed unless overridden by IMPLICIT statements
 ! HELP-NEXT: -finput-charset=<value> Specify the default character set for source files
@@ -105,6 +106,7 @@
 ! HELP-FC1-NEXT: -ffixed-form           Process source files in fixed form
 ! HELP-FC1-NEXT: -ffixed-line-length=<value>
 ! HELP-FC1-NEXT: Use <value> as character line width in fixed mode
+! HELP-FC1-NEXT: -ffp-contract=<value> Form fused FP ops (e.g. FMAs)
 ! HELP-FC1-NEXT: -ffree-form            Process source files in free form
 ! HELP-FC1-NEXT: -fget-definition <value> <value> <value>
 ! HELP-FC1-NEXT:                        Get the symbol definition from <line> <start-column> <end-column>
diff --git a/flang/test/Driver/flang_f_opts.f90 b/flang/test/Driver/flang_f_opts.f90
index a0544d653104..4493a519e201 100644
--- a/flang/test/Driver/flang_f_opts.f90
+++ b/flang/test/Driver/flang_f_opts.f90
@@ -1,8 +1,10 @@
 ! Test for warnings generated when parsing driver options. You can use this file for relatively small tests and to avoid creating
 ! new test files.
 
-! RUN: %flang -### -S -O4 %s 2>&1 | FileCheck %s
+! RUN: %flang -### -S -O4 -ffp-contract=on %s 2>&1 | FileCheck %s
 
+! CHECK: warning: the argument 'on' is not supported for option 'ffp-contract='. Mapping to 'ffp-contract=off'
 ! CHECK: warning: -O4 is equivalent to -O3
 ! CHECK-LABEL: "-fc1"
+! CHECK: -ffp-contract=off
 ! CHECK: -O3
diff --git a/flang/test/Driver/flang_fp_opts.f90 b/flang/test/Driver/flang_fp_opts.f90
new file mode 100644
index 000000000000..34987f4b0c43
--- /dev/null
+++ b/flang/test/Driver/flang_fp_opts.f90
@@ -0,0 +1,4 @@
+! Test for handling of floating point options within the frontend driver
+
+! RUN: %flang_fc1 -ffp-contract=fast %s 2>&1 | FileCheck %s
+! CHECK: ffp-contract= is not currently implemented
diff --git a/flang/test/Driver/frontend-forwarding.f90 b/flang/test/Driver/frontend-forwarding.f90
index 7d8243d84a15..b956940fd7d2 100644
--- a/flang/test/Driver/frontend-forwarding.f90
+++ b/flang/test/Driver/frontend-forwarding.f90
@@ -8,6 +8,7 @@
 ! RUN:     -fdefault-real-8 \
 ! RUN:     -flarge-sizes \
 ! RUN:     -fconvert=little-endian \
+! RUN:     -ffp-contract=fast \
 ! RUN:     -mllvm -print-before-all\
 ! RUN:     -P \
 ! RUN:   | FileCheck %s
@@ -18,5 +19,6 @@
 ! CHECK: "-fdefault-integer-8"
 ! CHECK: "-fdefault-real-8"
 ! CHECK: "-flarge-sizes"
+! CHECK: "-ffp-contract=fast"
 ! CHECK: "-fconvert=little-endian"
 ! CHECK:  "-mllvm" "-print-before-all"