[llvm] cdbed2d - Reapply af57dbf12e54 "Add support for options -frounding-math, ftrapping-math, -ffp-model=, and -ffp-exception-behavior="

Melanie Blower via llvm-commits llvm-commits at lists.llvm.org
Wed Dec 4 11:33:20 PST 2019


Author: Melanie Blower
Date: 2019-12-04T11:32:33-08:00
New Revision: cdbed2dd856c14687efd741c2d8321686102acb8

URL: https://github.com/llvm/llvm-project/commit/cdbed2dd856c14687efd741c2d8321686102acb8
DIFF: https://github.com/llvm/llvm-project/commit/cdbed2dd856c14687efd741c2d8321686102acb8.diff

LOG:         Reapply af57dbf12e54 "Add support for options -frounding-math, ftrapping-math, -ffp-model=, and -ffp-exception-behavior="

        Patch was reverted because https://bugs.llvm.org/show_bug.cgi?id=44048
        The original patch is modified to set the strictfp IR attribute
        explicitly in CodeGen instead of as a side effect of IRBuilder

        Differential Revision: https://reviews.llvm.org/D62731

Added: 
    clang/test/CodeGen/fpconstrained.c
    clang/test/CodeGen/fpconstrained.cpp
    clang/test/Driver/fp-model.c

Modified: 
    clang/docs/UsersManual.rst
    clang/include/clang/AST/Decl.h
    clang/include/clang/AST/DeclBase.h
    clang/include/clang/Basic/DiagnosticDriverKinds.td
    clang/include/clang/Basic/DiagnosticGroups.td
    clang/include/clang/Basic/LangOptions.def
    clang/include/clang/Basic/LangOptions.h
    clang/include/clang/Driver/Options.td
    clang/lib/AST/Decl.cpp
    clang/lib/CodeGen/CGCall.cpp
    clang/lib/CodeGen/CodeGenFunction.cpp
    clang/lib/CodeGen/CodeGenFunction.h
    clang/lib/Driver/ToolChains/Clang.cpp
    clang/lib/Frontend/CompilerInvocation.cpp
    clang/lib/Sema/SemaExpr.cpp
    clang/lib/Serialization/ASTReaderDecl.cpp
    clang/lib/Serialization/ASTWriterDecl.cpp
    clang/test/Driver/clang_f_opts.c
    clang/test/Driver/fast-math.c
    llvm/include/llvm/IR/IRBuilder.h
    llvm/include/llvm/Target/TargetOptions.h
    llvm/unittests/IR/IRBuilderTest.cpp

Removed: 
    


################################################################################
diff  --git a/clang/docs/UsersManual.rst b/clang/docs/UsersManual.rst
index 714681d7f4ce..62e2575c6b26 100644
--- a/clang/docs/UsersManual.rst
+++ b/clang/docs/UsersManual.rst
@@ -1231,10 +1231,10 @@ are listed below.
 
 **-f[no-]trapping-math**
 
-   ``-fno-trapping-math`` allows optimizations that assume that
-   floating point operations cannot generate traps such as divide-by-zero,
-   overflow and underflow. Defaults to ``-ftrapping-math``.
-   Currently this option has no effect.
+   Control floating point exception behavior. ``-fno-trapping-math`` allows optimizations that assume that floating point operations cannot generate traps such as divide-by-zero, overflow and underflow.
+
+- The option ``-ftrapping-math`` behaves identically to ``-ffp-exception-behavior=strict``.
+- The option ``-fno-trapping-math`` behaves identically to ``-ffp-exception-behavior=ignore``.   This is the default.
 
 .. option:: -ffp-contract=<value>
 
@@ -1319,6 +1319,52 @@ are listed below.
 
    Defaults to ``-fno-finite-math``.
 
+.. _opt_frounding-math:
+
+**-f[no-]rounding-math**
+
+Force floating-point operations to honor the dynamically-set rounding mode by default.
+
+The result of a floating-point operation often cannot be exactly represented in the result type and therefore must be rounded.  IEEE 754 describes 
diff erent rounding modes that control how to perform this rounding, not all of which are supported by all implementations.  C provides interfaces (``fesetround`` and ``fesetenv``) for dynamically controlling the rounding mode, and while it also recommends certain conventions for changing the rounding mode, these conventions are not typically enforced in the ABI.  Since the rounding mode changes the numerical result of operations, the compiler must understand something about it in order to optimize floating point operations.
+
+Note that floating-point operations performed as part of constant initialization are formally performed prior to the start of the program and are therefore not subject to the current rounding mode.  This includes the initialization of global variables and local ``static`` variables.  Floating-point operations in these contexts will be rounded using ``FE_TONEAREST``.
+
+- The option ``-fno-rounding-math`` allows the compiler to assume that the rounding mode is set to ``FE_TONEAREST``.  This is the default.
+- The option ``-frounding-math`` forces the compiler to honor the dynamically-set rounding mode.  This prevents optimizations which might affect results if the rounding mode changes or is 
diff erent from the default; for example, it prevents floating-point operations from being reordered across most calls and prevents constant-folding when the result is not exactly representable.
+
+.. option:: -ffp-model=<value>
+
+   Specify floating point behavior. ``-ffp-model`` is an umbrella
+   option that encompasses functionality provided by other, single
+   purpose, floating point options.  Valid values are: ``precise``, ``strict``,
+   and ``fast``.
+   Details:
+
+   * ``precise`` Disables optimizations that are not value-safe on floating-point data, although FP contraction (FMA) is enabled (``-ffp-contract=fast``).  This is the default behavior.
+   * ``strict`` Enables ``-frounding-math`` and ``-ffp-exception-behavior=strict``, and disables contractions (FMA).  All of the ``-ffast-math`` enablements are disabled.
+   * ``fast`` Behaves identically to specifying both ``-ffast-math`` and ``ffp-contract=fast``
+
+   Note: If your command line specifies multiple instances
+   of the ``-ffp-model`` option, or if your command line option specifies
+   ``-ffp-model`` and later on the command line selects a floating point
+   option that has the effect of negating part of the  ``ffp-model`` that
+   has been selected, then the compiler will issue a diagnostic warning
+   that the override has occurred.
+
+.. option:: -ffp-exception-behavior=<value>
+
+   Specify the floating-point exception behavior.
+
+   Valid values are: ``ignore``, ``maytrap``, and ``strict``.
+   The default value is ``ignore``.  Details:
+
+   * ``ignore`` The compiler assumes that the exception status flags will not be read and that floating point exceptions will be masked.
+   * ``maytrap`` The compiler avoids transformations that may raise exceptions that would not have been raised by the original code. Constant folding performed by the compiler is exempt from this option.
+   * ``strict`` The compiler ensures that all transformations strictly preserve the floating point exception semantics of the original code.
+
+
+
+
 .. _controlling-code-generation:
 
 Controlling Code Generation

diff  --git a/clang/include/clang/AST/Decl.h b/clang/include/clang/AST/Decl.h
index c1544c9ded94..f4913540bab4 100644
--- a/clang/include/clang/AST/Decl.h
+++ b/clang/include/clang/AST/Decl.h
@@ -2196,6 +2196,10 @@ class FunctionDecl : public DeclaratorDecl,
   bool usesSEHTry() const { return FunctionDeclBits.UsesSEHTry; }
   void setUsesSEHTry(bool UST) { FunctionDeclBits.UsesSEHTry = UST; }
 
+  /// Indicates the function uses Floating Point constrained intrinsics
+  bool usesFPIntrin() const { return FunctionDeclBits.UsesFPIntrin; }
+  void setUsesFPIntrin(bool Val) { FunctionDeclBits.UsesFPIntrin = Val; }
+
   /// Whether this function has been deleted.
   ///
   /// A function that is "deleted" (via the C++0x "= delete" syntax)

diff  --git a/clang/include/clang/AST/DeclBase.h b/clang/include/clang/AST/DeclBase.h
index adea10b33188..54cdb84b6f33 100644
--- a/clang/include/clang/AST/DeclBase.h
+++ b/clang/include/clang/AST/DeclBase.h
@@ -1534,10 +1534,13 @@ class DeclContext {
 
     /// Store the ODRHash after first calculation.
     uint64_t HasODRHash : 1;
+
+    /// Indicates if the function uses Floating Point Constrained Intrinsics
+    uint64_t UsesFPIntrin : 1;
   };
 
   /// Number of non-inherited bits in FunctionDeclBitfields.
-  enum { NumFunctionDeclBits = 25 };
+  enum { NumFunctionDeclBits = 26 };
 
   /// Stores the bits used by CXXConstructorDecl. If modified
   /// NumCXXConstructorDeclBits and the accessor
@@ -1554,7 +1557,7 @@ class DeclContext {
     /// exactly 64 bits and thus the width of NumCtorInitializers
     /// will need to be shrunk if some bit is added to NumDeclContextBitfields,
     /// NumFunctionDeclBitfields or CXXConstructorDeclBitfields.
-    uint64_t NumCtorInitializers : 23;
+    uint64_t NumCtorInitializers : 22;
     uint64_t IsInheritingConstructor : 1;
 
     /// Whether this constructor has a trail-allocated explicit specifier.

diff  --git a/clang/include/clang/Basic/DiagnosticDriverKinds.td b/clang/include/clang/Basic/DiagnosticDriverKinds.td
index 39242c972ea2..67faa872e57c 100644
--- a/clang/include/clang/Basic/DiagnosticDriverKinds.td
+++ b/clang/include/clang/Basic/DiagnosticDriverKinds.td
@@ -441,6 +441,10 @@ def warn_drv_experimental_isel_incomplete_opt : Warning<
   "-fexperimental-isel support is incomplete for this architecture at the current optimization level">,
   InGroup<ExperimentalISel>;
 
+def warn_drv_experimental_fp_control_incomplete_opt : Warning<
+  "Support for floating point control option %0 is incomplete and experimental">,
+  InGroup<ExperimentalFloatControl>;
+
 def warn_drv_moutline_unsupported_opt : Warning<
   "The '%0' architecture does not support -moutline; flag ignored">,
   InGroup<OptionIgnored>;

diff  --git a/clang/include/clang/Basic/DiagnosticGroups.td b/clang/include/clang/Basic/DiagnosticGroups.td
index 478b217a19f6..dec293f45af7 100644
--- a/clang/include/clang/Basic/DiagnosticGroups.td
+++ b/clang/include/clang/Basic/DiagnosticGroups.td
@@ -1109,6 +1109,9 @@ def SpirCompat : DiagGroup<"spir-compat">;
 // Warning for the experimental-isel options.
 def ExperimentalISel : DiagGroup<"experimental-isel">;
 
+// Warning for the experimental float control options.
+def ExperimentalFloatControl : DiagGroup<"experimental-float-control">;
+
 // A warning group specifically for warnings related to function
 // multiversioning.
 def FunctionMultiVersioning : DiagGroup<"function-multiversion">;

diff  --git a/clang/include/clang/Basic/LangOptions.def b/clang/include/clang/Basic/LangOptions.def
index 68d6ee1dce42..05d96b6c6a13 100644
--- a/clang/include/clang/Basic/LangOptions.def
+++ b/clang/include/clang/Basic/LangOptions.def
@@ -255,6 +255,8 @@ LANGOPT(SinglePrecisionConstants , 1, 0, "treating double-precision floating poi
 LANGOPT(FastRelaxedMath , 1, 0, "OpenCL fast relaxed math")
 /// FP_CONTRACT mode (on/off/fast).
 ENUM_LANGOPT(DefaultFPContractMode, FPContractModeKind, 2, FPC_Off, "FP contraction type")
+ENUM_LANGOPT(FPRoundingMode, FPRoundingModeKind, 3, FPR_ToNearest, "FP Rounding Mode type")
+ENUM_LANGOPT(FPExceptionMode, FPExceptionModeKind, 2, FPE_Ignore, "FP Exception Behavior Mode type")
 LANGOPT(NoBitFieldTypeAlign , 1, 0, "bit-field type alignment")
 LANGOPT(HexagonQdsp6Compat , 1, 0, "hexagon-qdsp6 backward compatibility")
 LANGOPT(ObjCAutoRefCount , 1, 0, "Objective-C automated reference counting")

diff  --git a/clang/include/clang/Basic/LangOptions.h b/clang/include/clang/Basic/LangOptions.h
index 95628280a4a0..ae4a4b2b9e87 100644
--- a/clang/include/clang/Basic/LangOptions.h
+++ b/clang/include/clang/Basic/LangOptions.h
@@ -190,6 +190,34 @@ class LangOptions : public LangOptionsBase {
     FEA_On
   };
 
+  // Values of the following enumerations correspond to metadata arguments
+  // specified for constrained floating-point intrinsics:
+  // http://llvm.org/docs/LangRef.html#constrained-floating-point-intrinsics.
+
+  /// Possible rounding modes.
+  enum FPRoundingModeKind {
+    /// Rounding to nearest, corresponds to "round.tonearest".
+    FPR_ToNearest,
+    /// Rounding toward -Inf, corresponds to "round.downward".
+    FPR_Downward,
+    /// Rounding toward +Inf, corresponds to "round.upward".
+    FPR_Upward,
+    /// Rounding toward zero, corresponds to "round.towardzero".
+    FPR_TowardZero,
+    /// Is determined by runtime environment, corresponds to "round.dynamic".
+    FPR_Dynamic
+  };
+
+  /// Possible floating point exception behavior.
+  enum FPExceptionModeKind {
+    /// Assume that floating-point exceptions are masked.
+    FPE_Ignore,
+    /// Transformations do not cause new exceptions but may hide some.
+    FPE_MayTrap,
+    /// Strictly preserve the floating-point exception semantics.
+    FPE_Strict
+  };
+
   enum class LaxVectorConversionKind {
     /// Permit no implicit vector bitcasts.
     None,

diff  --git a/clang/include/clang/Driver/Options.td b/clang/include/clang/Driver/Options.td
index a64d0acb06fe..8965131b9001 100644
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -929,6 +929,10 @@ def : Flag<["-"], "fextended-identifiers">, Group<clang_ignored_f_Group>;
 def : Flag<["-"], "fno-extended-identifiers">, Group<f_Group>, Flags<[Unsupported]>;
 def fhosted : Flag<["-"], "fhosted">, Group<f_Group>;
 def fdenormal_fp_math_EQ : Joined<["-"], "fdenormal-fp-math=">, Group<f_Group>, Flags<[CC1Option]>;
+def ffp_model_EQ : Joined<["-"], "ffp-model=">, Group<f_Group>, Flags<[DriverOption]>,
+  HelpText<"Controls the semantics of floating-point calculations.">;
+def ffp_exception_behavior_EQ : Joined<["-"], "ffp-exception-behavior=">, Group<f_Group>, Flags<[CC1Option]>,
+  HelpText<"Specifies the exception behavior of floating-point operations.">;
 def ffast_math : Flag<["-"], "ffast-math">, Group<f_Group>, Flags<[CC1Option]>,
   HelpText<"Allow aggressive, lossy floating-point optimizations">;
 def fno_fast_math : Flag<["-"], "fno-fast-math">, Group<f_Group>;
@@ -1154,6 +1158,8 @@ def fno_honor_infinities : Flag<["-"], "fno-honor-infinities">, Group<f_Group>;
 // This option was originally misspelt "infinites" [sic].
 def : Flag<["-"], "fhonor-infinites">, Alias<fhonor_infinities>;
 def : Flag<["-"], "fno-honor-infinites">, Alias<fno_honor_infinities>;
+def frounding_math : Flag<["-"], "frounding-math">, Group<f_Group>, Flags<[CC1Option]>;
+def fno_rounding_math : Flag<["-"], "fno-rounding-math">, Group<f_Group>, Flags<[CC1Option]>;
 def ftrapping_math : Flag<["-"], "ftrapping-math">, Group<f_Group>, Flags<[CC1Option]>;
 def fno_trapping_math : Flag<["-"], "fno-trapping-math">, Group<f_Group>, Flags<[CC1Option]>;
 def ffp_contract : Joined<["-"], "ffp-contract=">, Group<f_Group>,
@@ -3242,7 +3248,6 @@ defm profile_values : BooleanFFlag<"profile-values">, Group<clang_ignored_gcc_op
 defm regs_graph : BooleanFFlag<"regs-graph">, Group<clang_ignored_f_Group>;
 defm rename_registers : BooleanFFlag<"rename-registers">, Group<clang_ignored_gcc_optimization_f_Group>;
 defm ripa : BooleanFFlag<"ripa">, Group<clang_ignored_f_Group>;
-defm rounding_math : BooleanFFlag<"rounding-math">, Group<clang_ignored_gcc_optimization_f_Group>;
 defm schedule_insns : BooleanFFlag<"schedule-insns">, Group<clang_ignored_gcc_optimization_f_Group>;
 defm schedule_insns2 : BooleanFFlag<"schedule-insns2">, Group<clang_ignored_gcc_optimization_f_Group>;
 defm see : BooleanFFlag<"see">, Group<clang_ignored_f_Group>;

diff  --git a/clang/lib/AST/Decl.cpp b/clang/lib/AST/Decl.cpp
index bfcf7926861f..0301110b7067 100644
--- a/clang/lib/AST/Decl.cpp
+++ b/clang/lib/AST/Decl.cpp
@@ -2793,6 +2793,7 @@ FunctionDecl::FunctionDecl(Kind DK, ASTContext &C, DeclContext *DC,
   FunctionDeclBits.ConstexprKind = ConstexprKind;
   FunctionDeclBits.InstantiationIsPending = false;
   FunctionDeclBits.UsesSEHTry = false;
+  FunctionDeclBits.UsesFPIntrin = false;
   FunctionDeclBits.HasSkippedBody = false;
   FunctionDeclBits.WillHaveBody = false;
   FunctionDeclBits.IsMultiVersion = false;

diff  --git a/clang/lib/CodeGen/CGCall.cpp b/clang/lib/CodeGen/CGCall.cpp
index ca6b1d409c24..657c9260e6e6 100644
--- a/clang/lib/CodeGen/CGCall.cpp
+++ b/clang/lib/CodeGen/CGCall.cpp
@@ -4336,6 +4336,13 @@ RValue CodeGenFunction::EmitCall(const CGFunctionInfo &CallInfo,
                              Callee.getAbstractInfo(), Attrs, CallingConv,
                              /*AttrOnCallSite=*/true);
 
+  if (const FunctionDecl *FD = dyn_cast_or_null<FunctionDecl>(CurFuncDecl))
+    if (FD->usesFPIntrin())
+      // All calls within a strictfp function are marked strictfp
+      Attrs =
+        Attrs.addAttribute(getLLVMContext(), llvm::AttributeList::FunctionIndex,
+                           llvm::Attribute::StrictFP);
+
   // Apply some call-site-specific attributes.
   // TODO: work this into building the attribute set.
 
@@ -4385,6 +4392,13 @@ RValue CodeGenFunction::EmitCall(const CGFunctionInfo &CallInfo,
   SmallVector<llvm::OperandBundleDef, 1> BundleList =
       getBundlesForFunclet(CalleePtr);
 
+  if (const FunctionDecl *FD = dyn_cast_or_null<FunctionDecl>(CurFuncDecl))
+    if (FD->usesFPIntrin())
+      // All calls within a strictfp function are marked strictfp
+      Attrs =
+        Attrs.addAttribute(getLLVMContext(), llvm::AttributeList::FunctionIndex,
+                           llvm::Attribute::StrictFP);
+
   // Emit the actual call/invoke instruction.
   llvm::CallBase *CI;
   if (!InvokeDest) {

diff  --git a/clang/lib/CodeGen/CodeGenFunction.cpp b/clang/lib/CodeGen/CodeGenFunction.cpp
index 7f3be896a7b9..fd3020835a4d 100644
--- a/clang/lib/CodeGen/CodeGenFunction.cpp
+++ b/clang/lib/CodeGen/CodeGenFunction.cpp
@@ -33,6 +33,8 @@
 #include "clang/Frontend/FrontendDiagnostic.h"
 #include "llvm/IR/DataLayout.h"
 #include "llvm/IR/Dominators.h"
+#include "llvm/IR/FPEnv.h"
+#include "llvm/IR/IntrinsicInst.h"
 #include "llvm/IR/Intrinsics.h"
 #include "llvm/IR/MDBuilder.h"
 #include "llvm/IR/Operator.h"
@@ -87,6 +89,7 @@ CodeGenFunction::CodeGenFunction(CodeGenModule &cgm, bool suppressNewContext)
     FMF.setAllowReassoc();
   }
   Builder.setFastMathFlags(FMF);
+  SetFPModel();
 }
 
 CodeGenFunction::~CodeGenFunction() {
@@ -102,6 +105,51 @@ CodeGenFunction::~CodeGenFunction() {
     CGM.getOpenMPRuntime().functionFinished(*this);
 }
 
+// Map the LangOption for rounding mode into
+// the corresponding enum in the IR.
+static llvm::fp::RoundingMode ToConstrainedRoundingMD(
+  LangOptions::FPRoundingModeKind Kind) {
+
+  switch (Kind) {
+  case LangOptions::FPR_ToNearest:  return llvm::fp::rmToNearest;
+  case LangOptions::FPR_Downward:   return llvm::fp::rmDownward;
+  case LangOptions::FPR_Upward:     return llvm::fp::rmUpward;
+  case LangOptions::FPR_TowardZero: return llvm::fp::rmTowardZero;
+  case LangOptions::FPR_Dynamic:    return llvm::fp::rmDynamic;
+  }
+  llvm_unreachable("Unsupported FP RoundingMode");
+}
+
+// Map the LangOption for exception behavior into
+// the corresponding enum in the IR.
+static llvm::fp::ExceptionBehavior ToConstrainedExceptMD(
+  LangOptions::FPExceptionModeKind Kind) {
+
+  switch (Kind) {
+  case LangOptions::FPE_Ignore:  return llvm::fp::ebIgnore;
+  case LangOptions::FPE_MayTrap: return llvm::fp::ebMayTrap;
+  case LangOptions::FPE_Strict:  return llvm::fp::ebStrict;
+  }
+  llvm_unreachable("Unsupported FP Exception Behavior");
+}
+
+void CodeGenFunction::SetFPModel() {
+  auto fpRoundingMode = ToConstrainedRoundingMD(
+                          getLangOpts().getFPRoundingMode());
+  auto fpExceptionBehavior = ToConstrainedExceptMD(
+                               getLangOpts().getFPExceptionMode());
+
+  if (fpExceptionBehavior == llvm::fp::ebIgnore &&
+      fpRoundingMode == llvm::fp::rmToNearest)
+    // Constrained intrinsics are not used.
+    ;
+  else {
+    Builder.setIsFPConstrained(true);
+    Builder.setDefaultConstrainedRounding(fpRoundingMode);
+    Builder.setDefaultConstrainedExcept(fpExceptionBehavior);
+  }
+}
+
 CharUnits CodeGenFunction::getNaturalPointeeTypeAlignment(QualType T,
                                                     LValueBaseInfo *BaseInfo,
                                                     TBAAAccessInfo *TBAAInfo) {
@@ -823,6 +871,10 @@ void CodeGenFunction::StartFunction(GlobalDecl GD, QualType RetTy,
       if (FD->isMain())
         Fn->addFnAttr(llvm::Attribute::NoRecurse);
 
+  if (const FunctionDecl *FD = dyn_cast_or_null<FunctionDecl>(D))
+    if (FD->usesFPIntrin())
+      Fn->addFnAttr(llvm::Attribute::StrictFP);
+
   // If a custom alignment is used, force realigning to this alignment on
   // any main function which certainly will need it.
   if (const FunctionDecl *FD = dyn_cast_or_null<FunctionDecl>(D))

diff  --git a/clang/lib/CodeGen/CodeGenFunction.h b/clang/lib/CodeGen/CodeGenFunction.h
index 7a2627ccf58b..8f99b090b818 100644
--- a/clang/lib/CodeGen/CodeGenFunction.h
+++ b/clang/lib/CodeGen/CodeGenFunction.h
@@ -4169,6 +4169,9 @@ class CodeGenFunction : public CodeGenTypeCache {
   /// point operation, expressed as the maximum relative error in ulp.
   void SetFPAccuracy(llvm::Value *Val, float Accuracy);
 
+  /// SetFPModel - Control floating point behavior via fp-model settings.
+  void SetFPModel();
+
 private:
   llvm::MDNode *getRangeForLoadFromType(QualType Ty);
   void EmitReturnOfRValue(RValue RV, QualType Ty);

diff  --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
index 03a6de812047..5f8c0cb8a2c1 100644
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -2302,9 +2302,18 @@ static void RenderFloatingPointOptions(const ToolChain &TC, const Driver &D,
   bool AssociativeMath = false;
   bool ReciprocalMath = false;
   bool SignedZeros = true;
-  bool TrappingMath = true;
+  bool TrappingMath = false; // Implemented via -ffp-exception-behavior
+  bool TrappingMathPresent = false; // Is trapping-math in args, and not
+                                    // overriden by ffp-exception-behavior?
+  bool RoundingFPMath = false;
+  bool RoundingMathPresent = false; // Is rounding-math in args?
+  // -ffp-model values: strict, fast, precise
+  StringRef FPModel = "";
+  // -ffp-exception-behavior options: strict, maytrap, ignore
+  StringRef FPExceptionBehavior = "";
   StringRef DenormalFPMath = "";
   StringRef FPContract = "";
+  bool StrictFPModel = false;
 
   if (const Arg *A = Args.getLastArg(options::OPT_flimited_precision_EQ)) {
     CmdArgs.push_back("-mlimit-float-precision");
@@ -2312,7 +2321,73 @@ static void RenderFloatingPointOptions(const ToolChain &TC, const Driver &D,
   }
 
   for (const Arg *A : Args) {
-    switch (A->getOption().getID()) {
+    auto optID = A->getOption().getID();
+    bool PreciseFPModel = false;
+    switch (optID) {
+    default:
+      break;
+    case options::OPT_frounding_math:
+    case options::OPT_ftrapping_math:
+    case options::OPT_ffp_exception_behavior_EQ:
+      D.Diag(clang::diag::warn_drv_experimental_fp_control_incomplete_opt)
+          << A->getOption().getName();
+      break;
+    case options::OPT_ffp_model_EQ: {
+      D.Diag(clang::diag::warn_drv_experimental_fp_control_incomplete_opt)
+          << A->getOption().getName();
+      // If -ffp-model= is seen, reset to fno-fast-math
+      HonorINFs = true;
+      HonorNaNs = true;
+      // Turning *off* -ffast-math restores the toolchain default.
+      MathErrno = TC.IsMathErrnoDefault();
+      AssociativeMath = false;
+      ReciprocalMath = false;
+      SignedZeros = true;
+      // -fno_fast_math restores default denormal and fpcontract handling
+      DenormalFPMath = "";
+      FPContract = "";
+      StringRef Val = A->getValue();
+      if (OFastEnabled && !Val.equals("fast")) {
+          // Only -ffp-model=fast is compatible with OFast, ignore.
+        D.Diag(clang::diag::warn_drv_overriding_flag_option)
+          << Args.MakeArgString("-ffp-model=" + Val)
+          << "-Ofast";
+        break;
+      }
+      StrictFPModel = false;
+      PreciseFPModel = true;
+      // ffp-model= is a Driver option, it is entirely rewritten into more
+      // granular options before being passed into cc1.
+      // Use the gcc option in the switch below.
+      if (!FPModel.empty() && !FPModel.equals(Val)) {
+        D.Diag(clang::diag::warn_drv_overriding_flag_option)
+          << Args.MakeArgString("-ffp-model=" + FPModel)
+          << Args.MakeArgString("-ffp-model=" + Val);
+        FPContract = "";
+      }
+      if (Val.equals("fast")) {
+        optID = options::OPT_ffast_math;
+        FPModel = Val;
+        FPContract = "fast";
+      } else if (Val.equals("precise")) {
+        optID = options::OPT_ffp_contract;
+        FPModel = Val;
+        FPContract = "fast";
+        PreciseFPModel = true;
+      } else if (Val.equals("strict")) {
+        StrictFPModel = true;
+        optID = options::OPT_frounding_math;
+        FPExceptionBehavior = "strict";
+        FPModel = Val;
+        TrappingMath = true;
+      } else
+        D.Diag(diag::err_drv_unsupported_option_argument)
+            << A->getOption().getName() << Val;
+      break;
+      }
+    }
+
+    switch (optID) {
     // If this isn't an FP option skip the claim below
     default: continue;
 
@@ -2329,19 +2404,82 @@ static void RenderFloatingPointOptions(const ToolChain &TC, const Driver &D,
     case options::OPT_fno_reciprocal_math:  ReciprocalMath = false;   break;
     case options::OPT_fsigned_zeros:        SignedZeros = true;       break;
     case options::OPT_fno_signed_zeros:     SignedZeros = false;      break;
-    case options::OPT_ftrapping_math:       TrappingMath = true;      break;
-    case options::OPT_fno_trapping_math:    TrappingMath = false;     break;
+    case options::OPT_ftrapping_math:
+      if (!TrappingMathPresent && !FPExceptionBehavior.empty() &&
+          !FPExceptionBehavior.equals("strict"))
+        // Warn that previous value of option is overridden.
+        D.Diag(clang::diag::warn_drv_overriding_flag_option)
+          << Args.MakeArgString("-ffp-exception-behavior=" + FPExceptionBehavior)
+          << "-ftrapping-math";
+      TrappingMath = true;
+      TrappingMathPresent = true;
+      FPExceptionBehavior = "strict";
+      break;
+    case options::OPT_fno_trapping_math:
+      if (!TrappingMathPresent && !FPExceptionBehavior.empty() &&
+          !FPExceptionBehavior.equals("ignore"))
+        // Warn that previous value of option is overridden.
+        D.Diag(clang::diag::warn_drv_overriding_flag_option)
+          << Args.MakeArgString("-ffp-exception-behavior=" + FPExceptionBehavior)
+          << "-fno-trapping-math";
+      TrappingMath = false;
+      TrappingMathPresent = true;
+      FPExceptionBehavior = "ignore";
+      break;
+
+    case options::OPT_frounding_math:
+      RoundingFPMath = true;
+      RoundingMathPresent = true;
+      break;
+
+    case options::OPT_fno_rounding_math:
+      RoundingFPMath = false;
+      RoundingMathPresent = false;
+      break;
 
     case options::OPT_fdenormal_fp_math_EQ:
       DenormalFPMath = A->getValue();
       break;
 
-    // Validate and pass through -fp-contract option.
+    // Validate and pass through -ffp-contract option.
     case options::OPT_ffp_contract: {
       StringRef Val = A->getValue();
-      if (Val == "fast" || Val == "on" || Val == "off")
+      if (PreciseFPModel) {
+        // -ffp-model=precise enables ffp-contract=fast as a side effect
+        // the FPContract value has already been set to a string literal
+        // and the Val string isn't a pertinent value.
+        ;
+      } else if (Val.equals("fast") || Val.equals("on") || Val.equals("off"))
         FPContract = Val;
       else
+        D.Diag(diag::err_drv_unsupported_option_argument)
+           << A->getOption().getName() << Val;
+      break;
+    }
+
+    // Validate and pass through -ffp-model option.
+    case options::OPT_ffp_model_EQ:
+      // This should only occur in the error case
+      // since the optID has been replaced by a more granular
+      // floating point option.
+      break;
+
+    // Validate and pass through -ffp-exception-behavior option.
+    case options::OPT_ffp_exception_behavior_EQ: {
+      StringRef Val = A->getValue();
+      if (!TrappingMathPresent && !FPExceptionBehavior.empty() &&
+          !FPExceptionBehavior.equals(Val))
+        // Warn that previous value of option is overridden.
+        D.Diag(clang::diag::warn_drv_overriding_flag_option)
+          << Args.MakeArgString("-ffp-exception-behavior=" + FPExceptionBehavior)
+          << Args.MakeArgString("-ffp-exception-behavior=" + Val);
+      TrappingMath = TrappingMathPresent = false;
+      if (Val.equals("ignore") || Val.equals("maytrap"))
+        FPExceptionBehavior = Val;
+      else if (Val.equals("strict")) {
+        FPExceptionBehavior = Val;
+        TrappingMath = TrappingMathPresent = true;
+      } else
         D.Diag(diag::err_drv_unsupported_option_argument)
             << A->getOption().getName() << Val;
       break;
@@ -2361,12 +2499,14 @@ static void RenderFloatingPointOptions(const ToolChain &TC, const Driver &D,
       ReciprocalMath = true;
       SignedZeros = false;
       TrappingMath = false;
+      FPExceptionBehavior = "";
       break;
     case options::OPT_fno_unsafe_math_optimizations:
       AssociativeMath = false;
       ReciprocalMath = false;
       SignedZeros = true;
       TrappingMath = true;
+      FPExceptionBehavior = "strict";
       // -fno_unsafe_math_optimizations restores default denormal handling
       DenormalFPMath = "";
       break;
@@ -2384,6 +2524,7 @@ static void RenderFloatingPointOptions(const ToolChain &TC, const Driver &D,
       ReciprocalMath = true;
       SignedZeros = false;
       TrappingMath = false;
+      RoundingFPMath = false;
       // If fast-math is set then set the fp-contract mode to fast.
       FPContract = "fast";
       break;
@@ -2397,12 +2538,31 @@ static void RenderFloatingPointOptions(const ToolChain &TC, const Driver &D,
       AssociativeMath = false;
       ReciprocalMath = false;
       SignedZeros = true;
-      TrappingMath = true;
+      TrappingMath = false;
+      RoundingFPMath = false;
       // -fno_fast_math restores default denormal and fpcontract handling
       DenormalFPMath = "";
       FPContract = "";
       break;
     }
+    if (StrictFPModel) {
+      // If -ffp-model=strict has been specified on command line but
+      // subsequent options conflict then emit warning diagnostic.
+      if (HonorINFs && HonorNaNs &&
+        !AssociativeMath && !ReciprocalMath &&
+        SignedZeros && TrappingMath && RoundingFPMath &&
+        DenormalFPMath.empty() && FPContract.empty())
+        // OK: Current Arg doesn't conflict with -ffp-model=strict
+        ;
+      else {
+        StrictFPModel = false;
+        FPModel = "";
+        D.Diag(clang::diag::warn_drv_overriding_flag_option)
+            << "-ffp-model=strict" <<
+            ((A->getNumValues() == 0) ?  A->getSpelling()
+            : Args.MakeArgString(A->getSpelling() + A->getValue()));
+      }
+    }
 
     // If we handled this option claim it
     A->claim();
@@ -2430,7 +2590,11 @@ static void RenderFloatingPointOptions(const ToolChain &TC, const Driver &D,
   if (ReciprocalMath)
     CmdArgs.push_back("-freciprocal-math");
 
-  if (!TrappingMath)
+  if (TrappingMath) {
+    // FP Exception Behavior is also set to strict
+    assert(FPExceptionBehavior.equals("strict"));
+    CmdArgs.push_back("-ftrapping-math");
+  } else if (TrappingMathPresent)
     CmdArgs.push_back("-fno-trapping-math");
 
   if (!DenormalFPMath.empty())
@@ -2440,14 +2604,37 @@ static void RenderFloatingPointOptions(const ToolChain &TC, const Driver &D,
   if (!FPContract.empty())
     CmdArgs.push_back(Args.MakeArgString("-ffp-contract=" + FPContract));
 
+  if (!RoundingFPMath)
+    CmdArgs.push_back(Args.MakeArgString("-fno-rounding-math"));
+
+  if (RoundingFPMath && RoundingMathPresent)
+    CmdArgs.push_back(Args.MakeArgString("-frounding-math"));
+
+  if (!FPExceptionBehavior.empty())
+    CmdArgs.push_back(Args.MakeArgString("-ffp-exception-behavior=" +
+                      FPExceptionBehavior));
+
   ParseMRecip(D, Args, CmdArgs);
 
   // -ffast-math enables the __FAST_MATH__ preprocessor macro, but check for the
   // individual features enabled by -ffast-math instead of the option itself as
   // that's consistent with gcc's behaviour.
   if (!HonorINFs && !HonorNaNs && !MathErrno && AssociativeMath &&
-      ReciprocalMath && !SignedZeros && !TrappingMath)
+      ReciprocalMath && !SignedZeros && !TrappingMath && !RoundingFPMath) {
     CmdArgs.push_back("-ffast-math");
+    if (FPModel.equals("fast")) {
+      if (FPContract.equals("fast"))
+        // All set, do nothing.
+        ;
+      else if (FPContract.empty())
+        // Enable -ffp-contract=fast
+        CmdArgs.push_back(Args.MakeArgString("-ffp-contract=fast"));
+      else
+        D.Diag(clang::diag::warn_drv_overriding_flag_option)
+          << "-ffp-model=fast"
+          << Args.MakeArgString("-ffp-contract=" + FPContract);
+    }
+  }
 
   // Handle __FINITE_MATH_ONLY__ similarly.
   if (!HonorINFs && !HonorNaNs)

diff  --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
index 74831e78d8cb..198ae69b7655 100644
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -3145,6 +3145,34 @@ static void ParseLangArgs(LangOptions &Opts, ArgList &Args, InputKind IK,
       Diags.Report(diag::err_drv_invalid_value) << A->getAsString(Args) << Val;
   }
 
+  LangOptions::FPRoundingModeKind FPRM = LangOptions::FPR_ToNearest;
+  if (Args.hasArg(OPT_frounding_math)) {
+    FPRM = LangOptions::FPR_Dynamic;
+  }
+  Opts.setFPRoundingMode(FPRM);
+
+  if (Args.hasArg(OPT_ftrapping_math)) {
+    Opts.setFPExceptionMode(LangOptions::FPE_Strict);
+  }
+
+  if (Args.hasArg(OPT_fno_trapping_math)) {
+    Opts.setFPExceptionMode(LangOptions::FPE_Ignore);
+  }
+
+  LangOptions::FPExceptionModeKind FPEB = LangOptions::FPE_Ignore;
+  if (Arg *A = Args.getLastArg(OPT_ffp_exception_behavior_EQ)) {
+    StringRef Val = A->getValue();
+    if (Val.equals("ignore"))
+      FPEB = LangOptions::FPE_Ignore;
+    else if (Val.equals("maytrap"))
+      FPEB = LangOptions::FPE_MayTrap;
+    else if (Val.equals("strict"))
+      FPEB = LangOptions::FPE_Strict;
+    else
+      Diags.Report(diag::err_drv_invalid_value) << A->getAsString(Args) << Val;
+  }
+  Opts.setFPExceptionMode(FPEB);
+
   Opts.RetainCommentsFromSystemHeaders =
       Args.hasArg(OPT_fretain_comments_from_system_headers);
 

diff  --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index 7bbda127a540..c53a4b789bed 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -13037,6 +13037,16 @@ ExprResult Sema::CreateBuiltinBinOp(SourceLocation OpLoc,
   if (ResultTy.isNull() || LHS.isInvalid() || RHS.isInvalid())
     return ExprError();
 
+  if (ResultTy->isRealFloatingType() &&
+      (getLangOpts().getFPRoundingMode() != LangOptions::FPR_ToNearest ||
+       getLangOpts().getFPExceptionMode() != LangOptions::FPE_Ignore))
+    // Mark the current function as usng floating point constrained intrinsics
+    if (FunctionDecl *F = dyn_cast<FunctionDecl>(CurContext))
+{
+      F->setUsesFPIntrin(true);
+      printf("Enclosing function uses fp intrinsics\n");
+}
+
   // Some of the binary operations require promoting operands of half vector to
   // float vectors and truncating the result back to half vector. For now, we do
   // this only when HalfArgsAndReturn is set (that is, when the target is arm or

diff  --git a/clang/lib/Serialization/ASTReaderDecl.cpp b/clang/lib/Serialization/ASTReaderDecl.cpp
index 3f7a1ed7fd5c..d989f46c4ab4 100644
--- a/clang/lib/Serialization/ASTReaderDecl.cpp
+++ b/clang/lib/Serialization/ASTReaderDecl.cpp
@@ -886,6 +886,7 @@ void ASTDeclReader::VisitFunctionDecl(FunctionDecl *FD) {
 
   FD->ODRHash = Record.readInt();
   FD->setHasODRHash(true);
+  FD->setUsesFPIntrin(Record.readInt());
 
   switch ((FunctionDecl::TemplatedKind)Record.readInt()) {
   case FunctionDecl::TK_NonTemplate:

diff  --git a/clang/lib/Serialization/ASTWriterDecl.cpp b/clang/lib/Serialization/ASTWriterDecl.cpp
index 51902a607ca1..38eb64e52e4a 100644
--- a/clang/lib/Serialization/ASTWriterDecl.cpp
+++ b/clang/lib/Serialization/ASTWriterDecl.cpp
@@ -559,6 +559,7 @@ void ASTDeclWriter::VisitFunctionDecl(FunctionDecl *D) {
   Record.AddSourceLocation(D->getEndLoc());
 
   Record.push_back(D->getODRHash());
+  Record.push_back(D->usesFPIntrin());
 
   Record.push_back(D->getTemplatedKind());
   switch (D->getTemplatedKind()) {

diff  --git a/clang/test/CodeGen/fpconstrained.c b/clang/test/CodeGen/fpconstrained.c
new file mode 100644
index 000000000000..b99e49fcfc6b
--- /dev/null
+++ b/clang/test/CodeGen/fpconstrained.c
@@ -0,0 +1,23 @@
+// RUN: %clang_cc1 -ftrapping-math -frounding-math -ffp-exception-behavior=strict -emit-llvm -o - %s | FileCheck %s -check-prefix=FPMODELSTRICT
+// RUN: %clang_cc1 -ffp-contract=fast -emit-llvm -o - %s | FileCheck %s -check-prefix=PRECISE
+// RUN: %clang_cc1 -ffast-math -ffp-contract=fast -emit-llvm -o - %s | FileCheck %s -check-prefix=FAST
+// RUN: %clang_cc1 -ffast-math -emit-llvm -o - %s | FileCheck %s -check-prefix=FAST
+// RUN: %clang_cc1 -ffast-math -ffp-contract=fast -ffp-exception-behavior=ignore -emit-llvm -o - %s | FileCheck %s -check-prefix=FAST
+// RUN: %clang_cc1 -ffast-math -ffp-contract=fast -ffp-exception-behavior=strict -emit-llvm -o - %s | FileCheck %s -check-prefix=EXCEPT
+// RUN: %clang_cc1 -ffast-math -ffp-contract=fast -ffp-exception-behavior=maytrap -emit-llvm -o - %s | FileCheck %s -check-prefix=MAYTRAP
+float f0, f1, f2;
+
+void foo() {
+  // CHECK-LABEL: define {{.*}}void @foo()
+
+  // MAYTRAP: llvm.experimental.constrained.fadd.f32(float %0, float %1, metadata !"round.tonearest", metadata !"fpexcept.maytrap")
+  // EXCEPT: llvm.experimental.constrained.fadd.f32(float %0, float %1, metadata !"round.tonearest", metadata !"fpexcept.strict")
+  // FPMODELSTRICT: llvm.experimental.constrained.fadd.f32(float %0, float %1, metadata !"round.dynamic", metadata !"fpexcept.strict")
+  // STRICTEXCEPT: llvm.experimental.constrained.fadd.f32(float %0, float %1, metadata !"round.dynamic", metadata !"fpexcept.strict")
+  // STRICTNOEXCEPT: llvm.experimental.constrained.fadd.f32(float %0, float %1, metadata !"round.dynamic", metadata !"fpexcept.ignore")
+  // PRECISE: fadd contract float %0, %1
+  // FAST: fadd fast
+  f0 = f1 + f2;
+
+  // CHECK: ret
+}

diff  --git a/clang/test/CodeGen/fpconstrained.cpp b/clang/test/CodeGen/fpconstrained.cpp
new file mode 100644
index 000000000000..97939a9f9eb9
--- /dev/null
+++ b/clang/test/CodeGen/fpconstrained.cpp
@@ -0,0 +1,47 @@
+// RUN: %clang_cc1 -x c++ -ftrapping-math -fexceptions -fcxx-exceptions -frounding-math -ffp-exception-behavior=strict -emit-llvm -o - %s | FileCheck %s -check-prefix=FPMODELSTRICT
+// RUN: %clang_cc1 -x c++ -ffp-contract=fast -fexceptions -fcxx-exceptions -emit-llvm -o - %s | FileCheck %s -check-prefix=PRECISE
+// RUN: %clang_cc1 -x c++ -ffast-math -fexceptions -fcxx-exceptions -ffp-contract=fast -emit-llvm -o - %s | FileCheck %s -check-prefix=FAST
+// RUN: %clang_cc1 -x c++ -ffast-math -fexceptions -fcxx-exceptions -emit-llvm -o - %s | FileCheck %s -check-prefix=FAST
+// RUN: %clang_cc1 -x c++ -ffast-math -fexceptions -fcxx-exceptions -ffp-contract=fast -ffp-exception-behavior=ignore -emit-llvm -o - %s | FileCheck %s -check-prefix=FAST
+// RUN: %clang_cc1 -x c++ -ffast-math -fexceptions -fcxx-exceptions -ffp-contract=fast -ffp-exception-behavior=strict -emit-llvm -o - %s | FileCheck %s -check-prefix=EXCEPT
+// RUN: %clang_cc1 -x c++ -ffast-math -fexceptions -fcxx-exceptions -ffp-contract=fast -ffp-exception-behavior=maytrap -emit-llvm -o - %s | FileCheck %s -check-prefix=MAYTRAP
+float f0, f1, f2;
+
+  template <class>
+  class aaaa {
+   public:
+    ~aaaa();
+    void b();
+  };
+  
+  template <class c>
+  aaaa<c>::~aaaa() { try {
+    b();
+  // CHECK-LABEL: define {{.*}}void @_ZN4aaaaIiED2Ev{{.*}}
+
+  } catch (...) {
+  // MAYTRAP: llvm.experimental.constrained.fadd.f32(float %4, float %5, metadata !"round.tonearest", metadata !"fpexcept.maytrap")
+  // EXCEPT: llvm.experimental.constrained.fadd.f32(float %4, float %5, metadata !"round.tonearest", metadata !"fpexcept.strict")
+  // FPMODELSTRICT: llvm.experimental.constrained.fadd.f32(float %4, float %5, metadata !"round.dynamic", metadata !"fpexcept.strict")
+  // STRICTEXCEPT: llvm.experimental.constrained.fadd.f32(float %4, float %5, metadata !"round.dynamic", metadata !"fpexcept.strict")
+  // STRICTNOEXCEPT: llvm.experimental.constrained.fadd.f32(float %4, float %5, metadata !"round.dynamic", metadata !"fpexcept.ignore")
+  // PRECISE: fadd contract float %4, %5
+  // FAST: fadd fast
+  f0 = f1 + f2;
+
+  // CHECK: ret void
+  }
+  }
+  
+  class d {
+   public:
+    d(const char *, int);
+    aaaa<int> e;
+  };
+  
+float foo() {
+  d x("", 1);
+  aaaa<int> a;
+  return f0;
+}
+

diff  --git a/clang/test/Driver/clang_f_opts.c b/clang/test/Driver/clang_f_opts.c
index 17feaab26ab7..fef9cbfb115e 100644
--- a/clang/test/Driver/clang_f_opts.c
+++ b/clang/test/Driver/clang_f_opts.c
@@ -198,6 +198,22 @@
 // CHECK-EXTENDED-IDENTIFIERS-NOT: "-fextended-identifiers"
 // CHECK-NO-EXTENDED-IDENTIFIERS: error: unsupported option '-fno-extended-identifiers'
 
+// RUN: %clang -### -S -frounding-math %s 2>&1 | FileCheck -check-prefix=CHECK-ROUNDING-MATH %s
+// CHECK-ROUNDING-MATH: "-cc1"
+// CHECK-ROUNDING-MATH: "-frounding-math"
+// CHECK-ROUNDING-MATH-NOT: "-fno-rounding-math"
+// RUN: %clang -### -S %s 2>&1 | FileCheck -check-prefix=CHECK-ROUNDING-MATH-NOT %s
+// RUN: %clang -### -S -ffp-model=imprecise %s 2>&1 | FileCheck -check-prefix=CHECK-FPMODEL %s
+// CHECK-FPMODEL: unsupported argument 'imprecise' to option 'ffp-model='
+// RUN: %clang -### -S -ffp-model=precise %s 2>&1 | FileCheck -check-prefix=IGNORE %s
+// RUN: %clang -### -S -ffp-model=strict %s 2>&1 | FileCheck -check-prefix=IGNORE %s
+// RUN: %clang -### -S -ffp-model=fast %s 2>&1 | FileCheck -check-prefix=IGNORE %s
+// RUN: %clang -### -S -ffp-exception-behavior=trap %s 2>&1 | FileCheck -check-prefix=CHECK-FPEB %s
+// CHECK-FPEB: unsupported argument 'trap' to option 'ffp-exception-behavior='
+// RUN: %clang -### -S -ffp-exception-behavior=maytrap %s 2>&1 | FileCheck -check-prefix=IGNORE %s
+// RUN: %clang -### -S -ffp-exception-behavior=ignore %s 2>&1 | FileCheck -check-prefix=IGNORE %s
+// RUN: %clang -### -S -ffp-exception-behavior=strict %s 2>&1 | FileCheck -check-prefix=IGNORE %s
+
 // RUN: %clang -### -S -fno-pascal-strings -mpascal-strings %s 2>&1 | FileCheck -check-prefix=CHECK-M-PASCAL-STRINGS %s
 // CHECK-M-PASCAL-STRINGS: "-fpascal-strings"
 
@@ -320,7 +336,6 @@
 // RUN: -fprefetch-loop-arrays                                                \
 // RUN: -fprofile-correction                                                  \
 // RUN: -fprofile-values                                                      \
-// RUN: -frounding-math                                                       \
 // RUN: -fschedule-insns                                                      \
 // RUN: -fsignaling-nans                                                      \
 // RUN: -fstrength-reduce                                                     \
@@ -385,7 +400,6 @@
 // CHECK-WARNING-DAG: optimization flag '-fprefetch-loop-arrays' is not supported
 // CHECK-WARNING-DAG: optimization flag '-fprofile-correction' is not supported
 // CHECK-WARNING-DAG: optimization flag '-fprofile-values' is not supported
-// CHECK-WARNING-DAG: optimization flag '-frounding-math' is not supported
 // CHECK-WARNING-DAG: optimization flag '-fschedule-insns' is not supported
 // CHECK-WARNING-DAG: optimization flag '-fsignaling-nans' is not supported
 // CHECK-WARNING-DAG: optimization flag '-fstrength-reduce' is not supported

diff  --git a/clang/test/Driver/fast-math.c b/clang/test/Driver/fast-math.c
index 916384216d8c..da47de260dc9 100644
--- a/clang/test/Driver/fast-math.c
+++ b/clang/test/Driver/fast-math.c
@@ -170,11 +170,11 @@
 // RUN: %clang -### -fno-fast-math -ffast-math -c %s 2>&1 \
 // RUN:   | FileCheck --check-prefix=CHECK-FAST-MATH %s
 // RUN: %clang -### -funsafe-math-optimizations -ffinite-math-only \
-// RUN:     -fno-math-errno -ffp-contract=fast -c %s 2>&1 \
+// RUN:     -fno-math-errno -ffp-contract=fast -fno-rounding-math -c %s 2>&1 \
 // RUN:   | FileCheck --check-prefix=CHECK-FAST-MATH %s
 // RUN: %clang -### -fno-honor-infinities -fno-honor-nans -fno-math-errno \
 // RUN:     -fassociative-math -freciprocal-math -fno-signed-zeros \
-// RUN:     -fno-trapping-math -ffp-contract=fast -c %s 2>&1 \
+// RUN:     -fno-trapping-math -ffp-contract=fast -fno-rounding-math -c %s 2>&1 \
 // RUN:   | FileCheck --check-prefix=CHECK-FAST-MATH %s
 // CHECK-FAST-MATH: "-cc1"
 // CHECK-FAST-MATH: "-ffast-math"

diff  --git a/clang/test/Driver/fp-model.c b/clang/test/Driver/fp-model.c
new file mode 100644
index 000000000000..a3984acef62b
--- /dev/null
+++ b/clang/test/Driver/fp-model.c
@@ -0,0 +1,137 @@
+// Test that incompatible combinations of -ffp-model= options
+// and other floating point options get a warning diagnostic.
+//
+// REQUIRES: clang-driver
+
+// RUN: %clang -### -ffp-model=fast -ffp-contract=off -c %s 2>&1 \
+// RUN:   | FileCheck --check-prefix=WARN %s
+// WARN: warning: overriding '-ffp-model=fast' option with '-ffp-contract=off' [-Woverriding-t-option]
+
+// RUN: %clang -### -ffp-model=fast -ffp-contract=on -c %s 2>&1 \
+// RUN:   | FileCheck --check-prefix=WARN1 %s
+// WARN1: warning: overriding '-ffp-model=fast' option with '-ffp-contract=on' [-Woverriding-t-option]
+
+// RUN: %clang -### -ffp-model=strict -fassociative-math -c %s 2>&1 \
+// RUN:   | FileCheck --check-prefix=WARN2 %s
+// WARN2: warning: overriding '-ffp-model=strict' option with '-fassociative-math' [-Woverriding-t-option]
+
+// RUN: %clang -### -ffp-model=strict -ffast-math -c %s 2>&1 \
+// RUN:   | FileCheck --check-prefix=WARN3 %s
+// WARN3: warning: overriding '-ffp-model=strict' option with '-ffast-math' [-Woverriding-t-option]
+
+// RUN: %clang -### -ffp-model=strict -ffinite-math-only -c %s 2>&1 \
+// RUN:   | FileCheck --check-prefix=WARN4 %s
+// WARN4: warning: overriding '-ffp-model=strict' option with '-ffinite-math-only' [-Woverriding-t-option]
+
+// RUN: %clang -### -ffp-model=strict -ffp-contract=fast -c %s 2>&1 \
+// RUN:   | FileCheck --check-prefix=WARN5 %s
+// WARN5: warning: overriding '-ffp-model=strict' option with '-ffp-contract=fast' [-Woverriding-t-option]
+
+// RUN: %clang -### -ffp-model=strict -ffp-contract=off -c %s 2>&1 \
+// RUN:   | FileCheck --check-prefix=WARN6 %s
+// WARN6: warning: overriding '-ffp-model=strict' option with '-ffp-contract=off' [-Woverriding-t-option]
+
+// RUN: %clang -### -ffp-model=strict -ffp-contract=on -c %s 2>&1 \
+// RUN:   | FileCheck --check-prefix=WARN7 %s
+// WARN7: warning: overriding '-ffp-model=strict' option with '-ffp-contract=on' [-Woverriding-t-option]
+
+// RUN: %clang -### -ffp-model=strict -fno-honor-infinities -c %s 2>&1 \
+// RUN:   | FileCheck --check-prefix=WARN8 %s
+// WARN8: warning: overriding '-ffp-model=strict' option with '-fno-honor-infinities' [-Woverriding-t-option]
+
+// RUN: %clang -### -ffp-model=strict -fno-honor-nans -c %s 2>&1 \
+// RUN:   | FileCheck --check-prefix=WARN9 %s
+// WARN9: warning: overriding '-ffp-model=strict' option with '-fno-honor-nans' [-Woverriding-t-option]
+
+// RUN: %clang -### -ffp-model=strict -fno-rounding-math -c %s 2>&1 \
+// RUN:   | FileCheck --check-prefix=WARNa %s
+// WARNa: warning: overriding '-ffp-model=strict' option with '-fno-rounding-math' [-Woverriding-t-option]
+
+// RUN: %clang -### -ffp-model=strict -fno-signed-zeros -c %s 2>&1 \
+// RUN:   | FileCheck --check-prefix=WARNb %s
+// WARNb: warning: overriding '-ffp-model=strict' option with '-fno-signed-zeros' [-Woverriding-t-option]
+
+// RUN: %clang -### -ffp-model=strict -fno-trapping-math -c %s 2>&1 \
+// RUN:   | FileCheck --check-prefix=WARNc %s
+// WARNc: warning: overriding '-ffp-model=strict' option with '-fno-trapping-math' [-Woverriding-t-option]
+
+// RUN: %clang -### -ffp-model=strict -freciprocal-math -c %s 2>&1 \
+// RUN:   | FileCheck --check-prefix=WARNd %s
+// WARNd: warning: overriding '-ffp-model=strict' option with '-freciprocal-math' [-Woverriding-t-option]
+
+// RUN: %clang -### -ffp-model=strict -funsafe-math-optimizations -c %s 2>&1 \
+// RUN:   | FileCheck --check-prefix=WARNe %s
+// WARNe: warning: overriding '-ffp-model=strict' option with '-funsafe-math-optimizations' [-Woverriding-t-option]
+
+// RUN: %clang -### -ffp-model=strict -Ofast -c %s 2>&1 \
+// RUN:   | FileCheck --check-prefix=WARNf %s
+// WARNf: warning: overriding '-ffp-model=strict' option with '-Ofast' [-Woverriding-t-option]
+
+// RUN: %clang -### -c %s 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-NOROUND %s
+// CHECK-NOROUND: "-cc1"
+// CHECK-NOROUND: "-fno-rounding-math"
+
+// RUN: %clang -### -frounding-math -c %s 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-ROUND --implicit-check-not ffp-exception-behavior=strict %s
+// CHECK-ROUND: "-cc1"
+// CHECK-ROUND: "-frounding-math"
+
+// RUN: %clang -### -ftrapping-math -c %s 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-TRAP %s
+// CHECK-TRAP: "-cc1"
+// CHECK-TRAP: "-ftrapping-math"
+// CHECK-TRAP: "-ffp-exception-behavior=strict"
+
+// RUN: %clang -### -nostdinc -ffp-model=fast -c %s 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-FPM-FAST %s
+// CHECK-FPM-FAST: "-cc1"
+// CHECK-FPM-FAST: "-menable-no-infs"
+// CHECK-FPM-FAST: "-menable-no-nans"
+// CHECK-FPM-FAST: "-menable-unsafe-fp-math"
+// CHECK-FPM-FAST: "-fno-signed-zeros"
+// CHECK-FPM-FAST: "-mreassociate"
+// CHECK-FPM-FAST: "-freciprocal-math"
+// CHECK-FPM-FAST: "-ffp-contract=fast"
+// CHECK-FPM-FAST: "-fno-rounding-math"
+// CHECK-FPM-FAST: "-ffast-math"
+// CHECK-FPM-FAST: "-ffinite-math-only"
+
+// RUN: %clang -### -nostdinc -ffp-model=precise -c %s 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-FPM-PRECISE %s
+// CHECK-FPM-PRECISE: "-cc1"
+// CHECK-FPM-PRECISE: "-ffp-contract=fast"
+// CHECK-FPM-PRECISE: "-fno-rounding-math"
+
+// RUN: %clang -### -nostdinc -ffp-model=strict -c %s 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-FPM-STRICT %s
+// CHECK-FPM-STRICT: "-cc1"
+// CHECK-FPM-STRICT: "-ftrapping-math"
+// CHECK-FPM-STRICT: "-frounding-math"
+// CHECK-FPM-STRICT: "-ffp-exception-behavior=strict"
+
+// RUN: %clang -### -nostdinc -ftrapping-math -ffp-exception-behavior=ignore -c %s 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-TRAP-IGNORE %s
+// CHECK-TRAP-IGNORE: "-cc1"
+// CHECK-TRAP-IGNORE: "-fno-rounding-math"
+// CHECK-TRAP-IGNORE: "-ffp-exception-behavior=ignore"
+
+
+// RUN: %clang -### -nostdinc -ffp-exception-behavior=strict -c %s 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-FEB-STRICT %s
+// CHECK-FEB-STRICT: "-cc1"
+// CHECK-FEB-STRICT: "-fno-rounding-math"
+// CHECK-FEB-STRICT: "-ffp-exception-behavior=strict"
+
+// RUN: %clang -### -nostdinc -ffp-exception-behavior=maytrap -c %s 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-FEB-MAYTRAP %s
+// CHECK-FEB-MAYTRAP: "-cc1"
+// CHECK-FEB-MAYTRAP: "-fno-rounding-math"
+// CHECK-FEB-MAYTRAP: "-ffp-exception-behavior=maytrap"
+
+// RUN: %clang -### -nostdinc -ffp-exception-behavior=ignore -c %s 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-FEB-IGNORE %s
+// CHECK-FEB-IGNORE: "-cc1"
+// CHECK-FEB-IGNORE: "-fno-rounding-math"
+// CHECK-FEB-IGNORE: "-ffp-exception-behavior=ignore"
+

diff  --git a/llvm/include/llvm/IR/IRBuilder.h b/llvm/include/llvm/IR/IRBuilder.h
index 2d9c72108d3d..24d39c2bc526 100644
--- a/llvm/include/llvm/IR/IRBuilder.h
+++ b/llvm/include/llvm/IR/IRBuilder.h
@@ -265,7 +265,6 @@ class IRBuilderBase {
   void setConstrainedFPCallAttr(CallInst *I) {
     if (!I->hasFnAttr(Attribute::StrictFP))
       I->addAttribute(AttributeList::FunctionIndex, Attribute::StrictFP);
-    setConstrainedFPFunctionAttr();
   }
 
   //===--------------------------------------------------------------------===//

diff  --git a/llvm/include/llvm/Target/TargetOptions.h b/llvm/include/llvm/Target/TargetOptions.h
index c395e5bcecf1..d1db4eceabb8 100644
--- a/llvm/include/llvm/Target/TargetOptions.h
+++ b/llvm/include/llvm/Target/TargetOptions.h
@@ -107,7 +107,7 @@ namespace llvm {
   public:
     TargetOptions()
         : PrintMachineCode(false), UnsafeFPMath(false), NoInfsFPMath(false),
-          NoNaNsFPMath(false), NoTrappingFPMath(false),
+          NoNaNsFPMath(false), NoTrappingFPMath(true),
           NoSignedZerosFPMath(false),
           HonorSignDependentRoundingFPMathOption(false), NoZerosInBSS(false),
           GuaranteedTailCallOpt(false), StackSymbolOrdering(true),

diff  --git a/llvm/unittests/IR/IRBuilderTest.cpp b/llvm/unittests/IR/IRBuilderTest.cpp
index d7712fda1270..814da64c7852 100644
--- a/llvm/unittests/IR/IRBuilderTest.cpp
+++ b/llvm/unittests/IR/IRBuilderTest.cpp
@@ -183,6 +183,8 @@ TEST_F(IRBuilderTest, ConstrainedFP) {
   // See if we get constrained intrinsics instead of non-constrained
   // instructions.
   Builder.setIsFPConstrained(true);
+  auto Parent = BB->getParent();
+  Parent->addFnAttr(Attribute::StrictFP);
 
   V = Builder.CreateFAdd(V, V);
   ASSERT_TRUE(isa<IntrinsicInst>(V));
@@ -233,7 +235,8 @@ TEST_F(IRBuilderTest, ConstrainedFP) {
   AttributeSet CallAttrs = II->getAttributes().getFnAttributes();
   EXPECT_EQ(CallAttrs.hasAttribute(Attribute::StrictFP), true);
 
-  // Verify attributes on the containing function are created automatically.
+  // Verify attributes on the containing function are created when requested.
+  Builder.setConstrainedFPFunctionAttr();
   AttributeList Attrs = BB->getParent()->getAttributes();
   AttributeSet FnAttrs = Attrs.getFnAttributes();
   EXPECT_EQ(FnAttrs.hasAttribute(Attribute::StrictFP), true);


        


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