1 files changed, 52 insertions, 0 deletions
diff --git a/clang/lib/CodeGen/CodeGenFunction.cpp b/clang/lib/CodeGen/CodeGenFunction.cpp
index 7f3be896a7b..fd3020835a4 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))