2 files changed, 58 insertions, 0 deletions
diff --git a/clang/lib/CodeGen/CodeGenFunction.cpp b/clang/lib/CodeGen/CodeGenFunction.cpp
index 89dd06948ba..b7f70b8aa5c 100644
--- a/clang/lib/CodeGen/CodeGenFunction.cpp
+++ b/clang/lib/CodeGen/CodeGenFunction.cpp
@@ -33,6 +33,7 @@
 #include "clang/Frontend/FrontendDiagnostic.h"
 #include "llvm/IR/DataLayout.h"
 #include "llvm/IR/Dominators.h"
+#include "llvm/IR/IntrinsicInst.h"
 #include "llvm/IR/Intrinsics.h"
 #include "llvm/IR/MDBuilder.h"
 #include "llvm/IR/Operator.h"
@@ -87,6 +88,7 @@ CodeGenFunction::CodeGenFunction(CodeGenModule &cgm, bool suppressNewContext)
     FMF.setAllowReassoc();
   }
   Builder.setFastMathFlags(FMF);
+  SetFPModel();
 }
 
 CodeGenFunction::~CodeGenFunction() {
@@ -102,6 +104,59 @@ CodeGenFunction::~CodeGenFunction() {
     CGM.getOpenMPRuntime().functionFinished(*this);
 }
 
+// Map the LangOption for rounding mode into
+// the corresponding enum in the IR.
+static llvm::ConstrainedFPIntrinsic::RoundingMode ToConstrainedRoundingMD(
+  LangOptions::FPRoundingModeKind Kind) {
+
+  switch (Kind) {
+  case LangOptions::FPR_ToNearest:
+    return llvm::ConstrainedFPIntrinsic::rmToNearest;
+  case LangOptions::FPR_Downward:
+    return llvm::ConstrainedFPIntrinsic::rmDownward;
+  case LangOptions::FPR_Upward:
+    return llvm::ConstrainedFPIntrinsic::rmUpward;
+  case LangOptions::FPR_TowardZero:
+    return llvm::ConstrainedFPIntrinsic::rmTowardZero;
+  case LangOptions::FPR_Dynamic:
+    return llvm::ConstrainedFPIntrinsic::rmDynamic;
+  }
+  llvm_unreachable("Unsupported FP RoundingMode");
+}
+
+// Map the LangOption for exception behavior into
+// the corresponding enum in the IR.
+static llvm::ConstrainedFPIntrinsic::ExceptionBehavior ToConstrainedExceptMD(
+  LangOptions::FPExceptionModeKind Kind) {
+
+  switch (Kind) {
+  case LangOptions::FPE_Ignore:
+    return llvm::ConstrainedFPIntrinsic::ebIgnore;
+  case LangOptions::FPE_MayTrap:
+    return llvm::ConstrainedFPIntrinsic::ebMayTrap;
+  case LangOptions::FPE_Strict:
+    return llvm::ConstrainedFPIntrinsic::ebStrict;
+  }
+  llvm_unreachable("Unsupported FP Exception Behavior");
+}
+
+void CodeGenFunction::SetFPModel() {
+  auto fpRoundingMode = ToConstrainedRoundingMD(
+                          getLangOpts().getFPRoundingMode());
+  auto fpExceptionBehavior = ToConstrainedExceptMD(
+                               getLangOpts().getFPExceptionMode());
+
+  if (fpExceptionBehavior == llvm::ConstrainedFPIntrinsic::ebIgnore &&
+      fpRoundingMode == llvm::ConstrainedFPIntrinsic::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) {
diff --git a/clang/lib/CodeGen/CodeGenFunction.h b/clang/lib/CodeGen/CodeGenFunction.h
index 5c3d1764fad..b05475a3000 100644
--- a/clang/lib/CodeGen/CodeGenFunction.h
+++ b/clang/lib/CodeGen/CodeGenFunction.h
@@ -4156,6 +4156,9 @@ public:
   /// 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);