Index: lib/AsmParser/LLParser.cpp
===================================================================
--- lib/AsmParser/LLParser.cpp
+++ lib/AsmParser/LLParser.cpp
@@ -3003,11 +3003,17 @@
       break;
     default: llvm_unreachable("Unknown binary operator!");
     }
+
     unsigned Flags = 0;
     if (NUW)   Flags |= OverflowingBinaryOperator::NoUnsignedWrap;
     if (NSW)   Flags |= OverflowingBinaryOperator::NoSignedWrap;
     if (Exact) Flags |= PossiblyExactOperator::IsExact;
-    Constant *C = ConstantExpr::get(Opc, Val0, Val1, Flags);
+
+    FastMathFlags FMF;
+    FMF.setKeepExceptions();
+    FMF.setKeepRounding();
+
+    Constant *C = ConstantExpr::get(Opc, Val0, Val1, Flags, nullptr, FMF);
     ID.ConstantVal = C;
     ID.Kind = ValID::t_Constant;
     return false;
Index: lib/Bitcode/Reader/BitcodeReader.cpp
===================================================================
--- lib/Bitcode/Reader/BitcodeReader.cpp
+++ lib/Bitcode/Reader/BitcodeReader.cpp
@@ -2642,7 +2642,10 @@
               Flags |= SDivOperator::IsExact;
           }
         }
-        V = ConstantExpr::get(Opc, LHS, RHS, Flags);
+        FastMathFlags FMF;
+        FMF.setKeepExceptions();
+        FMF.setKeepRounding();
+        V = ConstantExpr::get(Opc, LHS, RHS, Flags, nullptr, FMF);
       }
       break;
     }
Index: test/Assembler/do-not-fold-fp-consts.ll
===================================================================
--- /dev/null
+++ test/Assembler/do-not-fold-fp-consts.ll
@@ -0,0 +1,36 @@
+; RUN: llvm-as < %s | llvm-dis | FileCheck %s
+
+define double @do-not-fold-fadd() {
+; CHECK-LABEL: @do-not-fold-fadd
+; CHECK: fadd
+entry:
+  ret double fadd (double 1.000000e+308, double 1.000000e+308)
+}
+
+define double @do-not-fold-fsub() {
+; CHECK-LABEL: @do-not-fold-fsub
+; CHECK: fsub
+entry:
+  ret double fsub (double 1.000000e-308, double 1.000000e+308)
+}
+
+define double @do-not-fold-fmul() {
+; CHECK-LABEL: @do-not-fold-fmul
+; CHECK: fmul
+entry:
+  ret double fmul (double 1.000000e+300, double 1.000000e+300)
+}
+
+define double @do-not-fold-fdiv() {
+; CHECK-LABEL: @do-not-fold-fdiv
+; CHECK: fdiv
+entry:
+  ret double fdiv (double 1.000000e+300, double 1.000000e-300)
+}
+
+define double @do-not-fold-frem() {
+; CHECK-LABEL: @do-not-fold-frem
+; CHECK: frem
+entry:
+  ret double frem (double 1.000000e+300, double 1.000000e-300)
+}