Add option 'exceptions' to pragma clang fp

[sepavloff]

Summary

Pragma 'clang fp' is extended to support a new option, 'exceptions'. It
allows to specify floating point exception behavior more flexibly.

[mibintc]

clang/docs/LanguageExtensions.rst

3223

do you mean pragma clang fp ...

clang/lib/Parse/ParsePragma.cpp

3054

Did you consider adding ActOnPragmaFPExceptions?

[sepavloff]

clang/docs/LanguageExtensions.rst

3223

Sure. Thank you!

clang/lib/Parse/ParsePragma.cpp

3054

The existing method setExceptionMode does everything that we need. Do you think it should be renamed to ActOnPragmaFPExceptions? Are there any advantages for this?

[mibintc]

clang/lib/Parse/ParsePragma.cpp

3054

I think it's easier to understand if it's written to parallel the other 2 fp pragmas that have similar semantics (contract and reassociate).

[sepavloff]

Added ActOnPragmaFPExceptions

[sepavloff]

clang/lib/Parse/ParsePragma.cpp

3054

It makes sense. This is a parser semantic action, they usually have names ActOn.... I didn't rename setExceptionMode , as in future we might need to set exception behavior from a place other than Parser.

clang/docs/LanguageExtensions.rst

 enabled for the translation unit with the ``-fassociative-math`` flag.
 The pragma can take two values: ``on`` and ``off``.
 
 .. code-block:: c++
 
   float f(float x, float y, float z)
   {
     // Enable floating point reassociation across statements
-    #pragma fp reassociate(on)
+    #pragma clang fp reassociate(on)
     float t = x + y;
     float v = t + z;
   }
 
 
 ``#pragma clang fp contract`` specifies whether the compiler should
 contract a multiply and an addition (or subtraction) into a fused FMA
 operation when supported by the target.
for(...) {
     d[i] += a;
   }
 
 
 The pragma can also be used with ``off`` which turns FP contraction off for a
 section of the code. This can be useful when fast contraction is otherwise
 enabled for the translation unit with the ``-ffp-contract=fast`` flag.
 
+
+``#pragma clang fp exceptions`` specifies floating point exception behavior. It
+may take one the the values: ``ignore``, ``maytrap`` or ``strict``. Meaning of
+these values is same as for `constrained floating point intrinsics <http://llvm.org/docs/LangRef.html#constrained-floating-point-intrinsics>`_.
+
+.. code-block:: c++
+
+  {
+    // Preserve floating point exceptions
+    #pragma clang fp exceptions(strict)
+    z = x + y;
+    if (fetestexcept(FE_OVERFLOW))
+    ...
+  }
+
+A ``#pragma clang fp`` pragma may contain any number of options:
+
+.. code-block:: c++
+
+  void func(float *dest, float a, float b) {
+    #pragma clang fp exceptions(maytrap) contract(fast) reassociate(on)
+    ...
+  }
+
+
 The ``#pragma float_control`` pragma allows precise floating-point
 semantics and floating-point exception behavior to be specified
 for a section of the source code. This pragma can only appear at file scope or
 at the start of a compound statement (excluding comments). When using within a
 compound statement, the pragma is active within the scope of the compound
 statement.  This pragma is modeled after a Microsoft pragma with the
 same spelling and syntax.  For pragmas specified at file scope, a stack
 is supported so that the ``pragma float_control`` settings can be pushed or popped.

clang/include/clang/Basic/DiagnosticParseKinds.td

def err_pragma_loop_missing_argument : Error<
   "missing argument; expected %select{an integer value|"
   "'enable'%select{|, 'full'}1%select{|, 'assume_safety'}2 or 'disable'}0">;
 def err_pragma_loop_invalid_option : Error<
   "%select{invalid|missing}0 option%select{ %1|}0; expected vectorize, "
   "vectorize_width, interleave, interleave_count, unroll, unroll_count, "
   "pipeline, pipeline_initiation_interval, vectorize_predicate, or distribute">;
 
 def err_pragma_fp_invalid_option : Error<
-  "%select{invalid|missing}0 option%select{ %1|}0; expected 'contract' or 'reassociate'">;
+  "%select{invalid|missing}0 option%select{ %1|}0; expected 'contract', 'reassociate' or 'exceptions'">;
 def err_pragma_fp_invalid_argument : Error<
-  "unexpected argument '%0' to '#pragma clang fp %1'; "
+  "unexpected argument '%0' to '#pragma clang fp %1'; expected "
   "%select{"
-  "expected 'fast' or 'on' or 'off'|"
-  "expected 'on' or 'off'}2">;
+  "'fast' or 'on' or 'off'|"
+  "'on' or 'off'|"
+  "'ignore', 'maytrap' or 'strict'}2">;
 
 def err_pragma_invalid_keyword : Error<
   "invalid argument; expected 'enable'%select{|, 'full'}0%select{|, 'assume_safety'}1 or 'disable'">;
 def err_pragma_pipeline_invalid_keyword : Error<
     "invalid argument; expected 'disable'">;
 
 // Pragma unroll support.
 def warn_pragma_unroll_cuda_value_in_parens : Warning<

clang/include/clang/Sema/Sema.h

   /// Called on well formed
   /// \#pragma clang fp reassociate
   void ActOnPragmaFPReassociate(SourceLocation Loc, bool IsEnabled);
 
   /// ActOnPragmaFenvAccess - Called on well formed
   /// \#pragma STDC FENV_ACCESS
   void ActOnPragmaFEnvAccess(SourceLocation Loc, bool IsEnabled);
 
+  /// Called on well formed '\#pragma clang fp' that has option 'exceptions'.
+  void ActOnPragmaFPExceptions(SourceLocation Loc,
+                               LangOptions::FPExceptionModeKind);
+
   /// Called to set constant rounding mode for floating point operations.
   void setRoundingMode(SourceLocation Loc, llvm::RoundingMode);
 
   /// Called to set exception behavior for floating point operations.
   void setExceptionMode(SourceLocation Loc, LangOptions::FPExceptionModeKind);
 
   /// AddAlignmentAttributesForRecord - Adds any needed alignment attributes to
   /// a the record decl, to handle '\#pragma pack' and '\#pragma options align'.

clang/lib/Parse/ParsePragma.cpp

void PragmaOptimizeHandler::HandlePragma(Preprocessor &PP,
   }
 
   Actions.ActOnPragmaOptimize(IsOn, FirstToken.getLocation());
 }
 
 namespace {
 /// Used as the annotation value for tok::annot_pragma_fp.
 struct TokFPAnnotValue {
-  enum FlagKinds { Contract, Reassociate };
+  enum FlagKinds { Contract, Reassociate, Exceptions };
   enum FlagValues { On, Off, Fast };
 
-  FlagKinds FlagKind;
-  FlagValues FlagValue;
+  llvm::Optional<LangOptions::FPModeKind> ContractValue;
+  llvm::Optional<LangOptions::FPModeKind> ReassociateValue;
+  llvm::Optional<LangOptions::FPExceptionModeKind> ExceptionsValue;
 };
 } // end anonymous namespace
 
 void PragmaFPHandler::HandlePragma(Preprocessor &PP,
                                    PragmaIntroducer Introducer, Token &Tok) {
   // fp
   Token PragmaName = Tok;
   SmallVector<Token, 1> TokenList;
 
   PP.Lex(Tok);
   if (Tok.isNot(tok::identifier)) {
     PP.Diag(Tok.getLocation(), diag::err_pragma_fp_invalid_option)
         << /*MissingOption=*/true << "";
     return;
   }
 
+  auto *AnnotValue = new (PP.getPreprocessorAllocator()) TokFPAnnotValue;
   while (Tok.is(tok::identifier)) {
     IdentifierInfo *OptionInfo = Tok.getIdentifierInfo();
 
     auto FlagKind =
         llvm::StringSwitch<llvm::Optional<TokFPAnnotValue::FlagKinds>>(
             OptionInfo->getName())
             .Case("contract", TokFPAnnotValue::Contract)
             .Case("reassociate", TokFPAnnotValue::Reassociate)
+            .Case("exceptions", TokFPAnnotValue::Exceptions)
             .Default(None);
     if (!FlagKind) {
       PP.Diag(Tok.getLocation(), diag::err_pragma_fp_invalid_option)
           << /*MissingOption=*/false << OptionInfo;
       return;
     }
     PP.Lex(Tok);
 
     // Read '('
     if (Tok.isNot(tok::l_paren)) {
       PP.Diag(Tok.getLocation(), diag::err_expected) << tok::l_paren;
       return;
     }
     PP.Lex(Tok);
 
     if (Tok.isNot(tok::identifier)) {
       PP.Diag(Tok.getLocation(), diag::err_pragma_fp_invalid_argument)
           << PP.getSpelling(Tok) << OptionInfo->getName()
-          << (FlagKind == TokFPAnnotValue::Reassociate);
+          << static_cast<int>(*FlagKind);
       return;
     }
     const IdentifierInfo *II = Tok.getIdentifierInfo();
 
-    auto FlagValue =
-        llvm::StringSwitch<llvm::Optional<TokFPAnnotValue::FlagValues>>(
+    if (FlagKind == TokFPAnnotValue::Contract) {
+      AnnotValue->ContractValue =
+          llvm::StringSwitch<llvm::Optional<LangOptions::FPModeKind>>(
               II->getName())
-            .Case("on", TokFPAnnotValue::On)
-            .Case("off", TokFPAnnotValue::Off)
-            .Case("fast", TokFPAnnotValue::Fast)
+              .Case("on", LangOptions::FPModeKind::FPM_On)
+              .Case("off", LangOptions::FPModeKind::FPM_Off)
+              .Case("fast", LangOptions::FPModeKind::FPM_Fast)
               .Default(llvm::None);
-
-    if (!FlagValue || (FlagKind == TokFPAnnotValue::Reassociate &&
-                       FlagValue == TokFPAnnotValue::Fast)) {
+      if (!AnnotValue->ContractValue) {
         PP.Diag(Tok.getLocation(), diag::err_pragma_fp_invalid_argument)
-          << PP.getSpelling(Tok) << OptionInfo->getName()
-          << (FlagKind == TokFPAnnotValue::Reassociate);
+            << PP.getSpelling(Tok) << OptionInfo->getName() << *FlagKind;
+        return;
+      }
+    } else if (FlagKind == TokFPAnnotValue::Reassociate) {
+      AnnotValue->ReassociateValue =
+          llvm::StringSwitch<llvm::Optional<LangOptions::FPModeKind>>(
+              II->getName())
+              .Case("on", LangOptions::FPModeKind::FPM_On)
+              .Case("off", LangOptions::FPModeKind::FPM_Off)
+              .Default(llvm::None);
+      if (!AnnotValue->ReassociateValue) {
+        PP.Diag(Tok.getLocation(), diag::err_pragma_fp_invalid_argument)
+            << PP.getSpelling(Tok) << OptionInfo->getName() << *FlagKind;
+        return;
+      }
+    } else if (FlagKind == TokFPAnnotValue::Exceptions) {
+      AnnotValue->ExceptionsValue =
+          llvm::StringSwitch<llvm::Optional<LangOptions::FPExceptionModeKind>>(
+              II->getName())
+              .Case("ignore", LangOptions::FPE_Ignore)
+              .Case("maytrap", LangOptions::FPE_MayTrap)
+              .Case("strict", LangOptions::FPE_Strict)
+              .Default(llvm::None);
+      if (!AnnotValue->ExceptionsValue) {
+        PP.Diag(Tok.getLocation(), diag::err_pragma_fp_invalid_argument)
+            << PP.getSpelling(Tok) << OptionInfo->getName() << *FlagKind;
         return;
       }
+    }
     PP.Lex(Tok);
 
     // Read ')'
     if (Tok.isNot(tok::r_paren)) {
       PP.Diag(Tok.getLocation(), diag::err_expected) << tok::r_paren;
       return;
     }
     PP.Lex(Tok);
+  }
+
+  if (Tok.isNot(tok::eod)) {
+    PP.Diag(Tok.getLocation(), diag::warn_pragma_extra_tokens_at_eol)
+        << "clang fp";
+    return;
+  }
 
-    auto *AnnotValue = new (PP.getPreprocessorAllocator())
-        TokFPAnnotValue{*FlagKind, *FlagValue};
-    // Generate the fp annotation token.
-    Token FPTok;
-    FPTok.startToken();
-    FPTok.setKind(tok::annot_pragma_fp);
-    FPTok.setLocation(PragmaName.getLocation());
-    FPTok.setAnnotationEndLoc(PragmaName.getLocation());
-    FPTok.setAnnotationValue(reinterpret_cast<void *>(AnnotValue));
-    TokenList.push_back(FPTok);
-  }
-
-  if (Tok.isNot(tok::eod)) {
-    PP.Diag(Tok.getLocation(), diag::warn_pragma_extra_tokens_at_eol)
-        << "clang fp";
-    return;
-  }
 
   auto TokenArray = std::make_unique<Token[]>(TokenList.size());
   std::copy(TokenList.begin(), TokenList.end(), TokenArray.get());
 
   PP.EnterTokenStream(std::move(TokenArray), TokenList.size(),
                       /*DisableMacroExpansion=*/false, /*IsReinject=*/false);
 }
 
PP.EnterTokenStream(Toks, /*DisableMacroExpansion=*/true,
                       /*IsReinject=*/false);
 }
 
 void Parser::HandlePragmaFP() {
   assert(Tok.is(tok::annot_pragma_fp));
   auto *AnnotValue =
       reinterpret_cast<TokFPAnnotValue *>(Tok.getAnnotationValue());
 
-  if (AnnotValue->FlagKind == TokFPAnnotValue::Reassociate)
-    Actions.ActOnPragmaFPReassociate(
-        Tok.getLocation(), AnnotValue->FlagValue == TokFPAnnotValue::On);
-  else {
-    LangOptions::FPModeKind FPC;
-    switch (AnnotValue->FlagValue) {
-    case TokFPAnnotValue::Off:
-      FPC = LangOptions::FPM_Off;
-      break;
-    case TokFPAnnotValue::On:
-      FPC = LangOptions::FPM_On;
-      break;
-    case TokFPAnnotValue::Fast:
-      FPC = LangOptions::FPM_Fast;
-      break;
-    }
-    Actions.ActOnPragmaFPContract(Tok.getLocation(), FPC);
-  }
+  if (AnnotValue->ReassociateValue)
+    Actions.ActOnPragmaFPReassociate(Tok.getLocation(),
+                                     *AnnotValue->ReassociateValue ==
+                                         LangOptions::FPModeKind::FPM_On);
+  if (AnnotValue->ContractValue)
+    Actions.ActOnPragmaFPContract(Tok.getLocation(),
+                                  *AnnotValue->ContractValue);
+  if (AnnotValue->ExceptionsValue)
+    Actions.ActOnPragmaFPExceptions(Tok.getLocation(),
+                                    *AnnotValue->ExceptionsValue);
   ConsumeAnnotationToken();
 }
 
 /// Parses loop or unroll pragma hint value and fills in Info.
 static bool ParseLoopHintValue(Preprocessor &PP, Token &Tok, Token PragmaName,
                                Token Option, bool ValueInParens,
                                PragmaLoopHintInfo &Info) {
   SmallVector<Token, 1> ValueList;

clang/lib/Sema/SemaAttr.cpp

if (IsEnabled) {
     NewFPFeatures.setFPExceptionModeOverride(LangOptions::FPE_Strict);
   } else {
     NewFPFeatures.setAllowFEnvAccessOverride(false);
   }
   FpPragmaStack.Act(Loc, PSK_Set, StringRef(), NewFPFeatures);
   CurFPFeatures = NewFPFeatures.applyOverrides(LO);
 }
 
+void Sema::ActOnPragmaFPExceptions(SourceLocation Loc,
+                                   LangOptions::FPExceptionModeKind FPE) {
+  setExceptionMode(Loc, FPE);
+}
+
 void Sema::PushNamespaceVisibilityAttr(const VisibilityAttr *Attr,
                                        SourceLocation Loc) {
   // Visibility calculations will consider the namespace's visibility.
   // Here we just want to note that we're in a visibility context
   // which overrides any enclosing #pragma context, but doesn't itself
   // contribute visibility.
   PushPragmaVisibility(*this, NoVisibility, Loc);
 }

clang/test/CodeGen/pragma-fp-exc.cpp

+// RUN: %clang_cc1 -triple %itanium_abi_triple -emit-llvm -o - %s | FileCheck --check-prefix=CHECK-DEF %s
+// RUN: %clang_cc1 -triple %itanium_abi_triple -ffp-exception-behavior=strict -emit-llvm -o - %s | FileCheck --check-prefix=CHECK-STRICT %s
+
+float func_01(float x, float y, float z) {
+  float res = x + y;
+  {
+#pragma clang fp exceptions(maytrap)
+    res += z;
+  }
+  return res;
+}
+// CHECK-DEF-LABEL: @_Z7func_01fff
+// CHECK-DEF:       call float @llvm.experimental.constrained.fadd.f32(float {{.*}}, float {{.*}}, metadata !"round.tonearest", metadata !"fpexcept.ignore")
+// CHECK-DEF:       call float @llvm.experimental.constrained.fadd.f32(float {{.*}}, float {{.*}}, metadata !"round.tonearest", metadata !"fpexcept.maytrap")
+
+// CHECK-STRICT-LABEL: @_Z7func_01fff
+// CHECK-STRICT:       call float @llvm.experimental.constrained.fadd.f32(float {{.*}}, float {{.*}}, metadata !"round.tonearest", metadata !"fpexcept.strict")
+// CHECK-STRICT:       call float @llvm.experimental.constrained.fadd.f32(float {{.*}}, float {{.*}}, metadata !"round.tonearest", metadata !"fpexcept.maytrap")

clang/test/Parser/pragma-fp.cpp

 // RUN: %clang_cc1 -std=c++11 -verify %s
 
 void test_0(int *List, int Length) {
-/* expected-error@+1 {{missing option; expected 'contract' or 'reassociate'}} */
+/* expected-error@+1 {{missing option; expected 'contract', 'reassociate' or 'exceptions'}} */
 #pragma clang fp
   for (int i = 0; i < Length; i++) {
     List[i] = i;
   }
 }
 void test_1(int *List, int Length) {
-/* expected-error@+1 {{invalid option 'blah'; expected 'contract' or 'reassociate'}} */
+/* expected-error@+1 {{invalid option 'blah'; expected 'contract', 'reassociate' or 'exceptions'}} */
 #pragma clang fp blah
   for (int i = 0; i < Length; i++) {
     List[i] = i;
   }
 }
 
 void test_3(int *List, int Length) {
 /* expected-error@+1 {{expected '('}} */

 
 void test_8(int *List, int Length) {
   for (int i = 0; i < Length; i++) {
     List[i] = i;
 /* expected-error@+1 {{'#pragma clang fp' can only appear at file scope or at the start of a compound statement}} */
 #pragma clang fp contract(fast)
   }
 }
+
+void test_9(float *dest, float a, float b) {
+/* expected-error@+1 {{unexpected argument 'on' to '#pragma clang fp exceptions'; expected 'ignore', 'maytrap' or 'strict'}} */
+#pragma clang fp exceptions(on)
+  *dest = a + b;
+}
+
+void test_10(float *dest, float a, float b) {
+#pragma clang fp exceptions(maytrap) contract(fast) reassociate(on)
+  *dest = a + b;
+}