[flang] Add support for -mrecip[=<list>] (#143418)

This patch adds support for the -mrecip command line option. The parsing
of this options is equivalent to Clang's and it is implemented by
setting the "reciprocal-estimates" function attribute.

Also move the ParseMRecip(...) function to CommonArgs, so that Flang is
able to make use of it as well.

---------

Co-authored-by: Cameron McInally <[email protected]>

Author: mcinally

clang/include/clang/Driver/CommonArgs.h

@@ -273,9 +273,14 @@ void handleVectorizeSLPArgs(const llvm::opt::ArgList &Args,
 
 // Parse -mprefer-vector-width=. Return the Value string if well-formed.
 // Otherwise, return an empty string and issue a diagnosic message if needed.
-StringRef ParseMPreferVectorWidthOption(clang::DiagnosticsEngine &Diags,
+StringRef parseMPreferVectorWidthOption(clang::DiagnosticsEngine &Diags,
                                         const llvm::opt::ArgList &Args);
 
+// Parse -mrecip. Return the Value string if well-formed.
+// Otherwise, return an empty string and issue a diagnosic message if needed.
+StringRef parseMRecipOption(clang::DiagnosticsEngine &Diags,
+                            const llvm::opt::ArgList &Args);
+
 } // end namespace tools
 } // end namespace driver
 } // end namespace clang

clang/include/clang/Driver/Options.td

@@ -5477,9 +5477,10 @@ def mno_implicit_float : Flag<["-"], "mno-implicit-float">, Group<m_Group>,
   HelpText<"Don't generate implicit floating point or vector instructions">;
 def mimplicit_float : Flag<["-"], "mimplicit-float">, Group<m_Group>;
 def mrecip : Flag<["-"], "mrecip">, Group<m_Group>,
+  Visibility<[ClangOption, CC1Option, FlangOption, FC1Option]>,
   HelpText<"Equivalent to '-mrecip=all'">;
 def mrecip_EQ : CommaJoined<["-"], "mrecip=">, Group<m_Group>,
-  Visibility<[ClangOption, CC1Option]>,
+  Visibility<[ClangOption, CC1Option, FlangOption, FC1Option]>,
   HelpText<"Control use of approximate reciprocal and reciprocal square root instructions followed by <n> iterations of "
            "Newton-Raphson refinement. "
            "<value> = ( ['!'] ['vec-'] ('rcp'|'sqrt') [('h'|'s'|'d')] [':'<n>] ) | 'all' | 'default' | 'none'">,

clang/lib/Driver/ToolChains/Clang.cpp

@@ -125,145 +125,6 @@ forAllAssociatedToolChains(Compilation &C, const JobAction &JA,
   //
 }
 
-/// This is a helper function for validating the optional refinement step
-/// parameter in reciprocal argument strings. Return false if there is an error
-/// parsing the refinement step. Otherwise, return true and set the Position
-/// of the refinement step in the input string.
-static bool getRefinementStep(StringRef In, const Driver &D,
-                              const Arg &A, size_t &Position) {
-  const char RefinementStepToken = ':';
-  Position = In.find(RefinementStepToken);
-  if (Position != StringRef::npos) {
-    StringRef Option = A.getOption().getName();
-    StringRef RefStep = In.substr(Position + 1);
-    // Allow exactly one numeric character for the additional refinement
-    // step parameter. This is reasonable for all currently-supported
-    // operations and architectures because we would expect that a larger value
-    // of refinement steps would cause the estimate "optimization" to
-    // under-perform the native operation. Also, if the estimate does not
-    // converge quickly, it probably will not ever converge, so further
-    // refinement steps will not produce a better answer.
-    if (RefStep.size() != 1) {
-      D.Diag(diag::err_drv_invalid_value) << Option << RefStep;
-      return false;
-    }
-    char RefStepChar = RefStep[0];
-    if (RefStepChar < '0' || RefStepChar > '9') {
-      D.Diag(diag::err_drv_invalid_value) << Option << RefStep;
-      return false;
-    }
-  }
-  return true;
-}
-
-/// The -mrecip flag requires processing of many optional parameters.
-static void ParseMRecip(const Driver &D, const ArgList &Args,
-                        ArgStringList &OutStrings) {
-  StringRef DisabledPrefixIn = "!";
-  StringRef DisabledPrefixOut = "!";
-  StringRef EnabledPrefixOut = "";
-  StringRef Out = "-mrecip=";
-
-  Arg *A = Args.getLastArg(options::OPT_mrecip, options::OPT_mrecip_EQ);
-  if (!A)
-    return;
-
-  unsigned NumOptions = A->getNumValues();
-  if (NumOptions == 0) {
-    // No option is the same as "all".
-    OutStrings.push_back(Args.MakeArgString(Out + "all"));
-    return;
-  }
-
-  // Pass through "all", "none", or "default" with an optional refinement step.
-  if (NumOptions == 1) {
-    StringRef Val = A->getValue(0);
-    size_t RefStepLoc;
-    if (!getRefinementStep(Val, D, *A, RefStepLoc))
-      return;
-    StringRef ValBase = Val.slice(0, RefStepLoc);
-    if (ValBase == "all" || ValBase == "none" || ValBase == "default") {
-      OutStrings.push_back(Args.MakeArgString(Out + Val));
-      return;
-    }
-  }
-
-  // Each reciprocal type may be enabled or disabled individually.
-  // Check each input value for validity, concatenate them all back together,
-  // and pass through.
-
-  llvm::StringMap<bool> OptionStrings;
-  OptionStrings.insert(std::make_pair("divd", false));
-  OptionStrings.insert(std::make_pair("divf", false));
-  OptionStrings.insert(std::make_pair("divh", false));
-  OptionStrings.insert(std::make_pair("vec-divd", false));
-  OptionStrings.insert(std::make_pair("vec-divf", false));
-  OptionStrings.insert(std::make_pair("vec-divh", false));
-  OptionStrings.insert(std::make_pair("sqrtd", false));
-  OptionStrings.insert(std::make_pair("sqrtf", false));
-  OptionStrings.insert(std::make_pair("sqrth", false));
-  OptionStrings.insert(std::make_pair("vec-sqrtd", false));
-  OptionStrings.insert(std::make_pair("vec-sqrtf", false));
-  OptionStrings.insert(std::make_pair("vec-sqrth", false));
-
-  for (unsigned i = 0; i != NumOptions; ++i) {
-    StringRef Val = A->getValue(i);
-
-    bool IsDisabled = Val.starts_with(DisabledPrefixIn);
-    // Ignore the disablement token for string matching.
-    if (IsDisabled)
-      Val = Val.substr(1);
-
-    size_t RefStep;
-    if (!getRefinementStep(Val, D, *A, RefStep))
-      return;
-
-    StringRef ValBase = Val.slice(0, RefStep);
-    llvm::StringMap<bool>::iterator OptionIter = OptionStrings.find(ValBase);
-    if (OptionIter == OptionStrings.end()) {
-      // Try again specifying float suffix.
-      OptionIter = OptionStrings.find(ValBase.str() + 'f');
-      if (OptionIter == OptionStrings.end()) {
-        // The input name did not match any known option string.
-        D.Diag(diag::err_drv_unknown_argument) << Val;
-        return;
-      }
-      // The option was specified without a half or float or double suffix.
-      // Make sure that the double or half entry was not already specified.
-      // The float entry will be checked below.
-      if (OptionStrings[ValBase.str() + 'd'] ||
-          OptionStrings[ValBase.str() + 'h']) {
-        D.Diag(diag::err_drv_invalid_value) << A->getOption().getName() << Val;
-        return;
-      }
-    }
-
-    if (OptionIter->second == true) {
-      // Duplicate option specified.
-      D.Diag(diag::err_drv_invalid_value) << A->getOption().getName() << Val;
-      return;
-    }
-
-    // Mark the matched option as found. Do not allow duplicate specifiers.
-    OptionIter->second = true;
-
-    // If the precision was not specified, also mark the double and half entry
-    // as found.
-    if (ValBase.back() != 'f' && ValBase.back() != 'd' && ValBase.back() != 'h') {
-      OptionStrings[ValBase.str() + 'd'] = true;
-      OptionStrings[ValBase.str() + 'h'] = true;
-    }
-
-    // Build the output string.
-    StringRef Prefix = IsDisabled ? DisabledPrefixOut : EnabledPrefixOut;
-    Out = Args.MakeArgString(Out + Prefix + Val);
-    if (i != NumOptions - 1)
-      Out = Args.MakeArgString(Out + ",");
-  }
-
-  OutStrings.push_back(Args.MakeArgString(Out));
-}
-
 static bool
 shouldUseExceptionTablesForObjCExceptions(const ObjCRuntime &runtime,
                                           const llvm::Triple &Triple) {
@@ -3490,7 +3351,9 @@ static void RenderFloatingPointOptions(const ToolChain &TC, const Driver &D,
     CmdArgs.push_back(Args.MakeArgString("-fbfloat16-excess-precision=" +
                                          BFloat16ExcessPrecision));
 
-  ParseMRecip(D, Args, CmdArgs);
+  StringRef Recip = parseMRecipOption(D.getDiags(), Args);
+  if (!Recip.empty())
+    CmdArgs.push_back(Args.MakeArgString("-mrecip=" + Recip));
 
   // -ffast-math enables the __FAST_MATH__ preprocessor macro, but check for the
   // individual features enabled by -ffast-math instead of the option itself as
@@ -7588,7 +7451,7 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
   handleVectorizeLoopsArgs(Args, CmdArgs);
   handleVectorizeSLPArgs(Args, CmdArgs);
 
-  StringRef VecWidth = ParseMPreferVectorWidthOption(D.getDiags(), Args);
+  StringRef VecWidth = parseMPreferVectorWidthOption(D.getDiags(), Args);
   if (!VecWidth.empty())
     CmdArgs.push_back(Args.MakeArgString("-mprefer-vector-width=" + VecWidth));
 

clang/lib/Driver/ToolChains/CommonArgs.cpp

@@ -3170,7 +3170,7 @@ void tools::handleInterchangeLoopsArgs(const ArgList &Args,
 
 // Parse -mprefer-vector-width=. Return the Value string if well-formed.
 // Otherwise, return an empty string and issue a diagnosic message if needed.
-StringRef tools::ParseMPreferVectorWidthOption(clang::DiagnosticsEngine &Diags,
+StringRef tools::parseMPreferVectorWidthOption(clang::DiagnosticsEngine &Diags,
                                                const llvm::opt::ArgList &Args) {
   Arg *A = Args.getLastArg(clang::driver::options::OPT_mprefer_vector_width_EQ);
   if (!A)
@@ -3189,3 +3189,144 @@ StringRef tools::ParseMPreferVectorWidthOption(clang::DiagnosticsEngine &Diags,
 
   return Value;
 }
+
+// This is a helper function for validating the optional refinement step
+// parameter in reciprocal argument strings. Return false if there is an error
+// parsing the refinement step. Otherwise, return true and set the Position
+// of the refinement step in the input string.
+static bool getRefinementStep(StringRef In, clang::DiagnosticsEngine &Diags,
+                              const Arg &A, size_t &Position) {
+  const char RefinementStepToken = ':';
+  Position = In.find(RefinementStepToken);
+  if (Position != StringRef::npos) {
+    StringRef Option = A.getOption().getName();
+    StringRef RefStep = In.substr(Position + 1);
+    // Allow exactly one numeric character for the additional refinement
+    // step parameter. This is reasonable for all currently-supported
+    // operations and architectures because we would expect that a larger value
+    // of refinement steps would cause the estimate "optimization" to
+    // under-perform the native operation. Also, if the estimate does not
+    // converge quickly, it probably will not ever converge, so further
+    // refinement steps will not produce a better answer.
+    if (RefStep.size() != 1) {
+      Diags.Report(diag::err_drv_invalid_value) << Option << RefStep;
+      return false;
+    }
+    char RefStepChar = RefStep[0];
+    if (RefStepChar < '0' || RefStepChar > '9') {
+      Diags.Report(diag::err_drv_invalid_value) << Option << RefStep;
+      return false;
+    }
+  }
+  return true;
+}
+
+// Parse -mrecip. Return the Value string if well-formed.
+// Otherwise, return an empty string and issue a diagnosic message if needed.
+StringRef tools::parseMRecipOption(clang::DiagnosticsEngine &Diags,
+                                   const ArgList &Args) {
+  StringRef DisabledPrefixIn = "!";
+  StringRef DisabledPrefixOut = "!";
+  StringRef EnabledPrefixOut = "";
+  StringRef Out = "";
+
+  Arg *A = Args.getLastArg(options::OPT_mrecip, options::OPT_mrecip_EQ);
+  if (!A)
+    return "";
+
+  unsigned NumOptions = A->getNumValues();
+  if (NumOptions == 0) {
+    // No option is the same as "all".
+    return "all";
+  }
+
+  // Pass through "all", "none", or "default" with an optional refinement step.
+  if (NumOptions == 1) {
+    StringRef Val = A->getValue(0);
+    size_t RefStepLoc;
+    if (!getRefinementStep(Val, Diags, *A, RefStepLoc))
+      return "";
+    StringRef ValBase = Val.slice(0, RefStepLoc);
+    if (ValBase == "all" || ValBase == "none" || ValBase == "default") {
+      return Val;
+    }
+  }
+
+  // Each reciprocal type may be enabled or disabled individually.
+  // Check each input value for validity, concatenate them all back together,
+  // and pass through.
+
+  llvm::StringMap<bool> OptionStrings;
+  OptionStrings.insert(std::make_pair("divd", false));
+  OptionStrings.insert(std::make_pair("divf", false));
+  OptionStrings.insert(std::make_pair("divh", false));
+  OptionStrings.insert(std::make_pair("vec-divd", false));
+  OptionStrings.insert(std::make_pair("vec-divf", false));
+  OptionStrings.insert(std::make_pair("vec-divh", false));
+  OptionStrings.insert(std::make_pair("sqrtd", false));
+  OptionStrings.insert(std::make_pair("sqrtf", false));
+  OptionStrings.insert(std::make_pair("sqrth", false));
+  OptionStrings.insert(std::make_pair("vec-sqrtd", false));
+  OptionStrings.insert(std::make_pair("vec-sqrtf", false));
+  OptionStrings.insert(std::make_pair("vec-sqrth", false));
+
+  for (unsigned i = 0; i != NumOptions; ++i) {
+    StringRef Val = A->getValue(i);
+
+    bool IsDisabled = Val.starts_with(DisabledPrefixIn);
+    // Ignore the disablement token for string matching.
+    if (IsDisabled)
+      Val = Val.substr(1);
+
+    size_t RefStep;
+    if (!getRefinementStep(Val, Diags, *A, RefStep))
+      return "";
+
+    StringRef ValBase = Val.slice(0, RefStep);
+    llvm::StringMap<bool>::iterator OptionIter = OptionStrings.find(ValBase);
+    if (OptionIter == OptionStrings.end()) {
+      // Try again specifying float suffix.
+      OptionIter = OptionStrings.find(ValBase.str() + 'f');
+      if (OptionIter == OptionStrings.end()) {
+        // The input name did not match any known option string.
+        Diags.Report(diag::err_drv_unknown_argument) << Val;
+        return "";
+      }
+      // The option was specified without a half or float or double suffix.
+      // Make sure that the double or half entry was not already specified.
+      // The float entry will be checked below.
+      if (OptionStrings[ValBase.str() + 'd'] ||
+          OptionStrings[ValBase.str() + 'h']) {
+        Diags.Report(diag::err_drv_invalid_value)
+            << A->getOption().getName() << Val;
+        return "";
+      }
+    }
+
+    if (OptionIter->second == true) {
+      // Duplicate option specified.
+      Diags.Report(diag::err_drv_invalid_value)
+          << A->getOption().getName() << Val;
+      return "";
+    }
+
+    // Mark the matched option as found. Do not allow duplicate specifiers.
+    OptionIter->second = true;
+
+    // If the precision was not specified, also mark the double and half entry
+    // as found.
+    if (ValBase.back() != 'f' && ValBase.back() != 'd' &&
+        ValBase.back() != 'h') {
+      OptionStrings[ValBase.str() + 'd'] = true;
+      OptionStrings[ValBase.str() + 'h'] = true;
+    }
+
+    // Build the output string.
+    StringRef Prefix = IsDisabled ? DisabledPrefixOut : EnabledPrefixOut;
+    Out = Args.MakeArgString(Out + Prefix + Val);
+    if (i != NumOptions - 1)
+      Out = Args.MakeArgString(Out + ",");
+  }
+
+  return Out;
+}

clang/lib/Driver/ToolChains/Flang.cpp

@@ -695,6 +695,10 @@ static void addFloatingPointOptions(const Driver &D, const ArgList &Args,
     A->claim();
   }
 
+  StringRef Recip = parseMRecipOption(D.getDiags(), Args);
+  if (!Recip.empty())
+    CmdArgs.push_back(Args.MakeArgString("-mrecip=" + Recip));
+
   if (!HonorINFs && !HonorNaNs && AssociativeMath && ReciprocalMath &&
       ApproxFunc && !SignedZeros &&
       (FPContract == "fast" || FPContract.empty())) {

flang/include/flang/Frontend/CodeGenOptions.h

@@ -53,9 +53,12 @@ class CodeGenOptions : public CodeGenOptionsBase {
   /// The paths to the pass plugins that were registered using -fpass-plugin.
   std::vector<std::string> LLVMPassPlugins;
 
-  // The prefered vector width, if requested by -mprefer-vector-width.
+  /// The prefered vector width, if requested by -mprefer-vector-width.
   std::string PreferVectorWidth;
 
+  /// List of reciprocal estimate sub-options.
+  std::string Reciprocals;
+
   /// List of filenames passed in using the -fembed-offload-object option. These
   /// are offloading binaries containing device images and metadata.
   std::vector<std::string> OffloadObjects;

flang/include/flang/Optimizer/Transforms/Passes.td

@@ -429,6 +429,9 @@ def FunctionAttr : Pass<"function-attr", "mlir::func::FuncOp"> {
               "module.">,
        Option<"unsafeFPMath", "unsafe-fp-math", "bool", /*default=*/"false",
               "Set the unsafe-fp-math attribute on functions in the module.">,
+       Option<"reciprocals", "mrecip", "std::string", /*default=*/"",
+              "Set the reciprocal-estimates attribute on functions in the "
+              "module.">,
        Option<"preferVectorWidth", "prefer-vector-width", "std::string",
               /*default=*/"",
               "Set the prefer-vector-width attribute on functions in the "

flang/include/flang/Tools/CrossToolHelpers.h

@@ -102,6 +102,7 @@ struct MLIRToLLVMPassPipelineConfig : public FlangEPCallBacks {
     UnsafeFPMath = mathOpts.getAssociativeMath() &&
         mathOpts.getReciprocalMath() && NoSignedZerosFPMath &&
         ApproxFuncFPMath && mathOpts.getFPContractEnabled();
+    Reciprocals = opts.Reciprocals;
     PreferVectorWidth = opts.PreferVectorWidth;
     if (opts.InstrumentFunctions) {
       InstrumentFunctionEntry = "__cyg_profile_func_enter";
@@ -127,6 +128,8 @@ struct MLIRToLLVMPassPipelineConfig : public FlangEPCallBacks {
   bool NoSignedZerosFPMath =
       false; ///< Set no-signed-zeros-fp-math attribute for functions.
   bool UnsafeFPMath = false; ///< Set unsafe-fp-math attribute for functions.
+  std::string Reciprocals = ""; ///< Set reciprocal-estimate attribute for
+                                ///< functions.
   std::string PreferVectorWidth = ""; ///< Set prefer-vector-width attribute for
                                       ///< functions.
   bool NSWOnLoopVarInc = true; ///< Add nsw flag to loop variable increments.