clang: Treat ieee mode as the default for denormal-fp-math

[arsenm]

Summary

The IR hasn't switched the default yet, so explicitly add the ieee attributes.

I'm still not really sure how the target default denormal mode should
interact with -fno-unsafe-math-optimizations. The target may have
selected the default mode to be non-IEEE based on the flags or based
on its true behavior, but we don't know which is the case. Since the
only users of a non-IEEE mode without a flag still support IEEE mode,
just reset to IEEE.

[arsenm]

Rebase

[arsenm]

ping

[spatel]

llvm/include/llvm/ADT/FloatingPointMode.h

48

Can these constexpr diffs be separated out as an NFC preliminary commit?

[arsenm]

Split out constexpr change

[andrew.w.kaylor]

lgtm

[arsenm]

c64ca93053af235bac0ca4dcdcd21c8882478310

clang/include/clang/Basic/CodeGenOptions.h

public:
   std::string RecordCommandLine;
 
   std::map<std::string, std::string> DebugPrefixMap;
 
   /// The ABI to use for passing floating point arguments.
   std::string FloatABI;
 
   /// The floating-point denormal mode to use.
-  llvm::DenormalMode FPDenormalMode;
+  llvm::DenormalMode FPDenormalMode = llvm::DenormalMode::getIEEE();
 
-  /// The floating-point subnormal mode to use, for float.
-  llvm::DenormalMode FP32DenormalMode;
+  /// The floating-point denormal mode to use, for float.
+  llvm::DenormalMode FP32DenormalMode = llvm::DenormalMode::getIEEE();
 
   /// The float precision limit to use, if non-empty.
   std::string LimitFloatPrecision;
 
   struct BitcodeFileToLink {
     /// The filename of the bitcode file to link in.
     std::string Filename;
     /// If true, we set attributes functions in the bitcode library according to

clang/include/clang/Driver/ToolChain.h

public:
 
   /// Returns the output denormal handling type in the default floating point
   /// environment for the given \p FPType if given. Otherwise, the default
   /// assumed mode for any floating point type.
   virtual llvm::DenormalMode getDefaultDenormalModeForType(
       const llvm::opt::ArgList &DriverArgs,
       Action::OffloadKind DeviceOffloadKind,
       const llvm::fltSemantics *FPType = nullptr) const {
-    // FIXME: This should be IEEE when default handling is fixed.
-    return llvm::DenormalMode::getInvalid();
+    return llvm::DenormalMode::getIEEE();
   }
 };
 
 /// Set a ToolChain's effective triple. Reset it when the registration object
 /// is destroyed.
 class RegisterEffectiveTriple {
   const ToolChain &TC;
 

clang/lib/Driver/ToolChains/Clang.cpp

case options::OPT_ffp_model_EQ: {
       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 = DefaultDenormalFPMath;
       FPContract = "";
+      DenormalFPMath = DefaultDenormalFPMath;
+
+      // FIXME: The target may have picked a non-IEEE default mode here based on
+      // -cl-denorms-are-zero. Should the target consider -fp-model interaction?
+      DenormalFP32Math = DefaultDenormalFP32Math;
+
       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;
       }
for (const Arg *A : Args) {
     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 = DefaultDenormalFPMath;
-      DenormalFP32Math = DefaultDenormalFP32Math;
+
+      // The target may have opted to flush just f32 by default, so force IEEE.
+      DenormalFP32Math = llvm::DenormalMode::getIEEE();
       break;
 
     case options::OPT_Ofast:
       // If -Ofast is the optimization level, then -ffast-math should be enabled
       if (!OFastEnabled)
         continue;
       LLVM_FALLTHROUGH;
     case options::OPT_ffast_math:
case options::OPT_fno_fast_math:
       DenormalFPMath = DefaultDenormalFPMath;
       DenormalFP32Math = DefaultDenormalFP32Math;
       FPContract = "";
       break;
     }
     if (StrictFPModel) {
       // If -ffp-model=strict has been specified on command line but
       // subsequent options conflict then emit warning diagnostic.
-      // TODO: How should this interact with DenormalFP32Math?
       if (HonorINFs && HonorNaNs &&
         !AssociativeMath && !ReciprocalMath &&
         SignedZeros && TrappingMath && RoundingFPMath &&
-        (FPContract.equals("off") || FPContract.empty()))
+        (FPContract.equals("off") || FPContract.empty()) &&
+        DenormalFPMath == llvm::DenormalMode::getIEEE() &&
+        DenormalFP32Math == llvm::DenormalMode::getIEEE())
         // 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()
static void RenderFloatingPointOptions(const ToolChain &TC, const Driver &D,
   // TODO: Omit flag for the default IEEE instead
   if (DenormalFPMath.isValid()) {
     llvm::SmallString<64> DenormFlag;
     llvm::raw_svector_ostream ArgStr(DenormFlag);
     ArgStr << "-fdenormal-fp-math=" << DenormalFPMath;
     CmdArgs.push_back(Args.MakeArgString(ArgStr.str()));
   }
 
-  if (DenormalFP32Math.isValid()) {
+  // Add f32 specific denormal mode flag if it's different.
+  if (DenormalFP32Math != DenormalFPMath) {
     llvm::SmallString<64> DenormFlag;
     llvm::raw_svector_ostream ArgStr(DenormFlag);
     ArgStr << "-fdenormal-fp-math-f32=" << DenormalFP32Math;
     CmdArgs.push_back(Args.MakeArgString(ArgStr.str()));
   }
 
   if (!FPContract.empty())
     CmdArgs.push_back(Args.MakeArgString("-ffp-contract=" + FPContract));

clang/test/CodeGenCUDA/flush-denormals.cu

 // RUN: %clang_cc1 -fcuda-is-device \
 // RUN:   -triple nvptx-nvidia-cuda -emit-llvm -o - %s | \
-// RUN:   FileCheck -check-prefix=DEFAULT %s
+// RUN:   FileCheck -check-prefix=NOFTZ %s
 
 // RUN: %clang_cc1 -fcuda-is-device -fdenormal-fp-math-f32=ieee \
 // RUN:   -triple nvptx-nvidia-cuda -emit-llvm -o - %s | \
 // RUN:   FileCheck -check-prefix=NOFTZ %s
 
 // RUN: %clang_cc1 -fcuda-is-device -fdenormal-fp-math-f32=preserve-sign \
 // RUN:   -triple nvptx-nvidia-cuda -emit-llvm -o - %s | \
 // RUN:   FileCheck -check-prefix=FTZ %s
 
-// FIXME: Unspecified should default to ieee
 // RUN: %clang_cc1 -fcuda-is-device -x hip \
 // RUN:   -triple amdgcn-amd-amdhsa -target-cpu gfx900 -emit-llvm -o - %s | \
-// RUN:   FileCheck -check-prefix=AMDFTZ %s
+// RUN:   FileCheck -check-prefix=AMDNOFTZ %s
 
 // RUN: %clang_cc1 -fcuda-is-device -x hip \
 // RUN:   -triple amdgcn-amd-amdhsa -target-cpu gfx900 -fdenormal-fp-math-f32=ieee -emit-llvm -o - %s | \
 // RUN:   FileCheck -check-prefix=AMDNOFTZ %s
 
 // RUN: %clang_cc1 -fcuda-is-device -x hip -fdenormal-fp-math-f32=preserve-sign \
 // RUN:   -triple amdgcn-amd-amdhsa -target-cpu gfx900 -emit-llvm -o - %s | \
 // RUN:   FileCheck -check-prefix=AMDFTZ %s

 // -fcuda-flush-denormals-to-zero.
 
 // CHECK-LABEL: define void @foo() #0
 extern "C" __device__ void foo() {}
 
 // FTZ: attributes #0 = {{.*}} "denormal-fp-math-f32"="preserve-sign,preserve-sign"
 // NOFTZ: attributes #0 = {{.*}} "denormal-fp-math-f32"="ieee,ieee"
 
-
-// FIXME: This should be removed
-// DEFAULT-NOT: "denormal-fp-math-f32"
-
 // AMDNOFTZ: attributes #0 = {{.*}}+fp32-denormals{{.*}}+fp64-fp16-denormals
 // AMDFTZ: attributes #0 = {{.*}}+fp64-fp16-denormals{{.*}}-fp32-denormals
 
 // FTZ:!llvm.module.flags = !{{{.*}}[[MODFLAG:![0-9]+]]}
 // FTZ:[[MODFLAG]] = !{i32 4, !"nvvm-reflect-ftz", i32 1}
 
 // NOFTZ:!llvm.module.flags = !{{{.*}}[[MODFLAG:![0-9]+]]}
 // NOFTZ:[[MODFLAG]] = !{i32 4, !"nvvm-reflect-ftz", i32 0}

clang/test/CodeGenCUDA/propagate-metadata.cu

 // overrides the flag on the bitcode library.
 
 // Build the bitcode library.  This is not built in CUDA mode, otherwise it
 // might have incompatible attributes.  This mirrors how libdevice is built.
 // RUN: %clang_cc1 -x c++ -fconvergent-functions -emit-llvm-bc -ftrapping-math -DLIB \
 // RUN:   %s -o %t.bc -triple nvptx-unknown-unknown
 
 // RUN: %clang_cc1 -x cuda %s -emit-llvm -mlink-builtin-bitcode %t.bc -o - \
-// RUN:   -fno-trapping-math -fcuda-is-device -fdenormal-fp-math-f32=ieee -triple nvptx-unknown-unknown \
+// RUN:   -fno-trapping-math -fcuda-is-device -triple nvptx-unknown-unknown \
 // RUN: | FileCheck %s --check-prefix=CHECK --check-prefix=NOFTZ --check-prefix=NOFAST
 
 // RUN: %clang_cc1 -x cuda %s -emit-llvm -mlink-builtin-bitcode %t.bc \
 // RUN:   -fno-trapping-math -fdenormal-fp-math-f32=preserve-sign -o - \
 // RUN:   -fcuda-is-device -triple nvptx-unknown-unknown \
 // RUN: | FileCheck %s --check-prefix=CHECK --check-prefix=FTZ \
 // RUN:   --check-prefix=NOFAST
 

 // line.
 
 // Check the attribute list for kernel.
 // CHECK: attributes [[kattr]] = {
 
 // CHECK-SAME: convergent
 // CHECK-SAME: norecurse
 
-// FTZ-NOT: "denormal-fp-math"
-
+// FTZ: "denormal-fp-math"="ieee,ieee"
 // FTZ-SAME: "denormal-fp-math-f32"="preserve-sign,preserve-sign"
 // NOFTZ-SAME: "denormal-fp-math-f32"="ieee,ieee"
 
 // CHECK-SAME: "no-trapping-math"="true"
 
 // FAST-SAME: "unsafe-fp-math"="true"
 // NOFAST-NOT: "unsafe-fp-math"="true"
 
 // Check the attribute list for lib_fn.
 // CHECK: attributes [[fattr]] = {
 
 // CHECK-SAME: convergent
 // CHECK-NOT: norecurse
 
-// FTZ-NOT: "denormal-fp-math"
+// FTZ-SAME: "denormal-fp-math"="ieee,ieee"
+// NOFTZ-SAME: "denormal-fp-math"="ieee,ieee"
 
 // FTZ-SAME: "denormal-fp-math-f32"="preserve-sign,preserve-sign"
 // NOFTZ-SAME: "denormal-fp-math-f32"="ieee,ieee"
 
 // CHECK-SAME: "no-trapping-math"="true"
 
 // FAST-SAME: "unsafe-fp-math"="true"
 // NOFAST-NOT: "unsafe-fp-math"="true"

clang/test/CodeGenOpenCL/amdgpu-features.cl

 // REQUIRES: amdgpu-registered-target
 
 // Check that appropriate features are defined for every supported AMDGPU
 // "-target" and "-mcpu" options.
 
 // RUN: %clang_cc1 -triple amdgcn -target-cpu gfx904 -S -emit-llvm -o - %s | FileCheck --check-prefix=GFX904 %s
 // RUN: %clang_cc1 -triple amdgcn -target-cpu gfx906 -S -emit-llvm -o - %s | FileCheck --check-prefix=GFX906 %s
 // RUN: %clang_cc1 -triple amdgcn -target-cpu gfx908 -S -emit-llvm -o - %s | FileCheck --check-prefix=GFX908 %s
 // RUN: %clang_cc1 -triple amdgcn -target-cpu gfx1010 -S -emit-llvm -o - %s | FileCheck --check-prefix=GFX1010 %s
 // RUN: %clang_cc1 -triple amdgcn -target-cpu gfx1011 -S -emit-llvm -o - %s | FileCheck --check-prefix=GFX1011 %s
 // RUN: %clang_cc1 -triple amdgcn -target-cpu gfx1012 -S -emit-llvm -o - %s | FileCheck --check-prefix=GFX1012 %s
 // RUN: %clang_cc1 -triple amdgcn -target-cpu gfx801 -S -emit-llvm -o - %s | FileCheck --check-prefix=GFX801 %s
 // RUN: %clang_cc1 -triple amdgcn -target-cpu gfx700 -S -emit-llvm -o - %s | FileCheck --check-prefix=GFX700 %s
 // RUN: %clang_cc1 -triple amdgcn -target-cpu gfx600 -S -emit-llvm -o - %s | FileCheck --check-prefix=GFX600 %s
 // RUN: %clang_cc1 -triple amdgcn -target-cpu gfx601 -S -emit-llvm -o - %s | FileCheck --check-prefix=GFX601 %s
 
-// GFX904: "target-features"="+16-bit-insts,+ci-insts,+dpp,+flat-address-space,+fp64-fp16-denormals,+gfx8-insts,+gfx9-insts,+s-memrealtime,-fp32-denormals"
-// GFX906: "target-features"="+16-bit-insts,+ci-insts,+dl-insts,+dot1-insts,+dot2-insts,+dpp,+flat-address-space,+fp64-fp16-denormals,+gfx8-insts,+gfx9-insts,+s-memrealtime,-fp32-denormals"
-// GFX908: "target-features"="+16-bit-insts,+ci-insts,+dl-insts,+dot1-insts,+dot2-insts,+dot3-insts,+dot4-insts,+dot5-insts,+dot6-insts,+dpp,+flat-address-space,+fp64-fp16-denormals,+gfx8-insts,+gfx9-insts,+mai-insts,+s-memrealtime,-fp32-denormals"
-// GFX1010: "target-features"="+16-bit-insts,+ci-insts,+dl-insts,+dpp,+flat-address-space,+fp64-fp16-denormals,+gfx10-insts,+gfx8-insts,+gfx9-insts,+s-memrealtime,-fp32-denormals"
-// GFX1011: "target-features"="+16-bit-insts,+ci-insts,+dl-insts,+dot1-insts,+dot2-insts,+dot5-insts,+dot6-insts,+dpp,+flat-address-space,+fp64-fp16-denormals,+gfx10-insts,+gfx8-insts,+gfx9-insts,+s-memrealtime,-fp32-denormals"
-// GFX1012: "target-features"="+16-bit-insts,+ci-insts,+dl-insts,+dot1-insts,+dot2-insts,+dot5-insts,+dot6-insts,+dpp,+flat-address-space,+fp64-fp16-denormals,+gfx10-insts,+gfx8-insts,+gfx9-insts,+s-memrealtime,-fp32-denormals"
-// GFX801: "target-features"="+16-bit-insts,+ci-insts,+dpp,+flat-address-space,+fp64-fp16-denormals,+gfx8-insts,+s-memrealtime,-fp32-denormals"
+// GFX904: "target-features"="+16-bit-insts,+ci-insts,+dpp,+flat-address-space,+fp32-denormals,+fp64-fp16-denormals,+gfx8-insts,+gfx9-insts,+s-memrealtime"
+// GFX906: "target-features"="+16-bit-insts,+ci-insts,+dl-insts,+dot1-insts,+dot2-insts,+dpp,+flat-address-space,+fp32-denormals,+fp64-fp16-denormals,+gfx8-insts,+gfx9-insts,+s-memrealtime"
+// GFX908: "target-features"="+16-bit-insts,+ci-insts,+dl-insts,+dot1-insts,+dot2-insts,+dot3-insts,+dot4-insts,+dot5-insts,+dot6-insts,+dpp,+flat-address-space,+fp32-denormals,+fp64-fp16-denormals,+gfx8-insts,+gfx9-insts,+mai-insts,+s-memrealtime"
+// GFX1010: "target-features"="+16-bit-insts,+ci-insts,+dl-insts,+dpp,+flat-address-space,+fp32-denormals,+fp64-fp16-denormals,+gfx10-insts,+gfx8-insts,+gfx9-insts,+s-memrealtime"
+// GFX1011: "target-features"="+16-bit-insts,+ci-insts,+dl-insts,+dot1-insts,+dot2-insts,+dot5-insts,+dot6-insts,+dpp,+flat-address-space,+fp32-denormals,+fp64-fp16-denormals,+gfx10-insts,+gfx8-insts,+gfx9-insts,+s-memrealtime"
+// GFX1012: "target-features"="+16-bit-insts,+ci-insts,+dl-insts,+dot1-insts,+dot2-insts,+dot5-insts,+dot6-insts,+dpp,+flat-address-space,+fp32-denormals,+fp64-fp16-denormals,+gfx10-insts,+gfx8-insts,+gfx9-insts,+s-memrealtime"
+// GFX801: "target-features"="+16-bit-insts,+ci-insts,+dpp,+flat-address-space,+fp32-denormals,+fp64-fp16-denormals,+gfx8-insts,+s-memrealtime"
 // GFX700: "target-features"="+ci-insts,+flat-address-space,+fp64-fp16-denormals,-fp32-denormals"
 // GFX600: "target-features"="+fp64-fp16-denormals,-fp32-denormals"
 // GFX601: "target-features"="+fp64-fp16-denormals,-fp32-denormals"
 
 kernel void test() {}

clang/test/Driver/cuda-flush-denormals-to-zero.cu

 // Checks that cuda compilation does the right thing when passed
 // -fcuda-flush-denormals-to-zero. This should be translated to
 // -fdenormal-fp-math-f32=preserve-sign
 
 // RUN: %clang -no-canonical-prefixes -### -target x86_64-linux-gnu -c -march=haswell--cuda-gpu-arch=sm_20 -fcuda-flush-denormals-to-zero -nocudainc -nocudalib %s 2>&1 | FileCheck -check-prefix=FTZ %s
 // RUN: %clang -no-canonical-prefixes -### -target x86_64-linux-gnu -c -march=haswell--cuda-gpu-arch=sm_20 -fno-cuda-flush-denormals-to-zero -nocudainc -nocudalib %s 2>&1 | FileCheck -check-prefix=NOFTZ %s
 // RUN: %clang -no-canonical-prefixes -### -target x86_64-linux-gnu -c -march=haswell--cuda-gpu-arch=sm_10 -fcuda-flush-denormals-to-zero -nocudainc -nocudalib %s 2>&1 | FileCheck -check-prefix=FTZ %s
 // RUN: %clang -no-canonical-prefixes -### -target x86_64-linux-gnu -c -march=haswell--cuda-gpu-arch=sm_10 -fno-cuda-flush-denormals-to-zero -nocudainc -nocudalib %s 2>&1 | FileCheck -check-prefix=NOFTZ %s
 
 // CPUFTZ-NOT: -fdenormal-fp-math
 
+// FTZ-NOT: -fdenormal-fp-math-f32=
 // FTZ: "-fdenormal-fp-math-f32=preserve-sign,preserve-sign"
-// NOFTZ: "-fdenormal-fp-math=ieee,ieee"
+
+// The default of ieee is omitted
+// NOFTZ-NOT: "-fdenormal-fp-math"
+// NOFTZ-NOT: "-fdenormal-fp-math-f32"

clang/test/Driver/denormal-fp-math.c

 // RUN: %clang -### -target arm-unknown-linux-gnu -c %s -fdenormal-fp-math=ieee -v 2>&1 | FileCheck -check-prefix=CHECK-IEEE %s
 // RUN: %clang -### -target arm-unknown-linux-gnu -c %s -fdenormal-fp-math=preserve-sign -v 2>&1 | FileCheck -check-prefix=CHECK-PS %s
 // RUN: %clang -### -target arm-unknown-linux-gnu -c %s -fdenormal-fp-math=positive-zero -v 2>&1 | FileCheck -check-prefix=CHECK-PZ %s
 // RUN: %clang -### -target arm-unknown-linux-gnu -c %s -fdenormal-fp-math=ieee -fno-fast-math -v 2>&1 | FileCheck -check-prefix=CHECK-NO-UNSAFE %s
 // RUN: %clang -### -target arm-unknown-linux-gnu -c %s -fdenormal-fp-math=ieee -fno-unsafe-math-optimizations -v 2>&1 | FileCheck -check-prefix=CHECK-NO-UNSAFE %s
 // RUN: not %clang -target arm-unknown-linux-gnu -c %s -fdenormal-fp-math=foo -v 2>&1 | FileCheck -check-prefix=CHECK-INVALID0 %s
 // RUN: not %clang -target arm-unknown-linux-gnu -c %s -fdenormal-fp-math=ieee,foo -v 2>&1 | FileCheck -check-prefix=CHECK-INVALID1 %s
 // RUN: not %clang -target arm-unknown-linux-gnu -c %s -fdenormal-fp-math=foo,ieee -v 2>&1 | FileCheck -check-prefix=CHECK-INVALID2 %s
 // RUN: not %clang -target arm-unknown-linux-gnu -c %s -fdenormal-fp-math=foo,foo -v 2>&1 | FileCheck -check-prefix=CHECK-INVALID3 %s
 
-// CHECK-IEEE: -fdenormal-fp-math=ieee,ieee
+// TODO: ieee is the implied default, and the flag is not passed.
+// CHECK-IEEE: "-fdenormal-fp-math=ieee,ieee"
 // CHECK-PS: "-fdenormal-fp-math=preserve-sign,preserve-sign"
 // CHECK-PZ: "-fdenormal-fp-math=positive-zero,positive-zero"
 // CHECK-NO-UNSAFE-NOT: "-fdenormal-fp-math=ieee"
 // CHECK-INVALID0: error: invalid value 'foo' in '-fdenormal-fp-math=foo'
 // CHECK-INVALID1: error: invalid value 'ieee,foo' in '-fdenormal-fp-math=ieee,foo'
 // CHECK-INVALID2: error: invalid value 'foo,ieee' in '-fdenormal-fp-math=foo,ieee'
 // CHECK-INVALID3: error: invalid value 'foo,foo' in '-fdenormal-fp-math=foo,foo'

clang/test/Driver/fp-model.c

 // 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 -### -ffp-model=strict -fdenormal-fp-math=preserve-sign,preserve-sign -c %s 2>&1 \
+// RUN:   | FileCheck --check-prefix=WARN10 %s
+// WARN10: warning: overriding '-ffp-model=strict' option with '-fdenormal-fp-math=preserve-sign,preserve-sign' [-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"

llvm/include/llvm/ADT/FloatingPointMode.h

struct DenormalMode {
   /// default floating point environment.
   DenormalModeKind Output = DenormalModeKind::Invalid;
 
   /// Denormal treatment kind for floating point instruction inputs in the
   /// default floating-point environment. If this is not DenormalModeKind::IEEE,
   /// floating-point instructions implicitly treat the input value as 0.
   DenormalModeKind Input = DenormalModeKind::Invalid;
 
-  DenormalMode() = default;
-  DenormalMode(DenormalModeKind Out, DenormalModeKind In) :
+  constexpr DenormalMode() = default;
+  constexpr DenormalMode(DenormalModeKind Out, DenormalModeKind In) :
     Output(Out), Input(In) {}
 
 
-  static DenormalMode getInvalid() {
+  static constexpr DenormalMode getInvalid() {
     return DenormalMode(DenormalModeKind::Invalid, DenormalModeKind::Invalid);
   }
 
-  static DenormalMode getIEEE() {
+  static constexpr DenormalMode getIEEE() {
     return DenormalMode(DenormalModeKind::IEEE, DenormalModeKind::IEEE);
   }
 
-  static DenormalMode getPreserveSign() {
+  static constexpr DenormalMode getPreserveSign() {
     return DenormalMode(DenormalModeKind::PreserveSign,
                         DenormalModeKind::PreserveSign);
   }
 
-  static DenormalMode getPositiveZero() {
+  static constexpr DenormalMode getPositiveZero() {
     return DenormalMode(DenormalModeKind::PositiveZero,
                         DenormalModeKind::PositiveZero);
   }
 
   bool operator==(DenormalMode Other) const {
     return Output == Other.Output && Input == Other.Input;
   }