diff --git a/js/src/asmjs/Wasm.cpp b/js/src/asmjs/Wasm.cpp
index b789a5cc791b..0ac57cd8623c 100644
--- a/js/src/asmjs/Wasm.cpp
+++ b/js/src/asmjs/Wasm.cpp
@@ -289,21 +289,17 @@ DecodeExpr(FunctionDecoder& f)
       case Expr::F32Ceil:
       case Expr::F32Floor:
       case Expr::F32Sqrt:
-        return f.iter().readUnary(ValType::F32, nullptr);
       case Expr::F32Trunc:
-        return f.iter().notYetImplemented("trunc");
       case Expr::F32Nearest:
-        return f.iter().notYetImplemented("nearest");
+        return f.iter().readUnary(ValType::F32, nullptr);
       case Expr::F64Abs:
       case Expr::F64Neg:
       case Expr::F64Ceil:
       case Expr::F64Floor:
       case Expr::F64Sqrt:
-        return f.iter().readUnary(ValType::F64, nullptr);
       case Expr::F64Trunc:
-        return f.iter().notYetImplemented("trunc");
       case Expr::F64Nearest:
-        return f.iter().notYetImplemented("nearest");
+        return f.iter().readUnary(ValType::F64, nullptr);
       case Expr::I32Add:
       case Expr::I32Sub:
       case Expr::I32Mul:
diff --git a/js/src/asmjs/WasmBinaryIterator.cpp b/js/src/asmjs/WasmBinaryIterator.cpp
index 678525dead3f..f700f9ffd8d0 100644
--- a/js/src/asmjs/WasmBinaryIterator.cpp
+++ b/js/src/asmjs/WasmBinaryIterator.cpp
@@ -73,11 +73,15 @@ wasm::Classify(Expr expr)
       case Expr::F32Neg:
       case Expr::F32Ceil:
       case Expr::F32Floor:
+      case Expr::F32Trunc:
+      case Expr::F32Nearest:
       case Expr::F32Sqrt:
       case Expr::F64Abs:
       case Expr::F64Neg:
       case Expr::F64Ceil:
       case Expr::F64Floor:
+      case Expr::F64Trunc:
+      case Expr::F64Nearest:
       case Expr::F64Sqrt:
       case Expr::I32BitNot:
       case Expr::I32Abs:
@@ -459,10 +463,6 @@ wasm::Classify(Expr expr)
         return ExprKind::SimdComparison;
       case Expr::CurrentMemory:
       case Expr::GrowMemory:
-      case Expr::F32Trunc:
-      case Expr::F32Nearest:
-      case Expr::F64Trunc:
-      case Expr::F64Nearest:
         break;
     }
     MOZ_MAKE_COMPILER_ASSUME_IS_UNREACHABLE("unimplemented opcode");
diff --git a/js/src/asmjs/WasmIonCompile.cpp b/js/src/asmjs/WasmIonCompile.cpp
index 59b0b8ca5f79..e0605646a08b 100644
--- a/js/src/asmjs/WasmIonCompile.cpp
+++ b/js/src/asmjs/WasmIonCompile.cpp
@@ -3015,6 +3015,10 @@ EmitExpr(FunctionCompiler& f)
         return EmitUnaryMathBuiltinCall(f, exprOffset, SymbolicAddress::CeilF, ValType::F32);
       case Expr::F32Floor:
         return EmitUnaryMathBuiltinCall(f, exprOffset, SymbolicAddress::FloorF, ValType::F32);
+      case Expr::F32Trunc:
+        return EmitUnaryMathBuiltinCall(f, exprOffset, SymbolicAddress::TruncF, ValType::F32);
+      case Expr::F32Nearest:
+        return EmitUnaryMathBuiltinCall(f, exprOffset, SymbolicAddress::NearbyIntF, ValType::F32);
       case Expr::F32DemoteF64:
         return EmitConversion<MToFloat32>(f, ValType::F64, ValType::F32);
       case Expr::F32ConvertSI32:
@@ -3066,8 +3070,11 @@ EmitExpr(FunctionCompiler& f)
       case Expr::F64Ceil:
         return EmitUnaryMathBuiltinCall(f, exprOffset, SymbolicAddress::CeilD, ValType::F64);
       case Expr::F64Floor:
-        return EmitUnaryMathBuiltinCall(f, exprOffset, SymbolicAddress::FloorD,
-                                        ValType::F64);
+        return EmitUnaryMathBuiltinCall(f, exprOffset, SymbolicAddress::FloorD, ValType::F64);
+      case Expr::F64Trunc:
+        return EmitUnaryMathBuiltinCall(f, exprOffset, SymbolicAddress::TruncD, ValType::F64);
+      case Expr::F64Nearest:
+        return EmitUnaryMathBuiltinCall(f, exprOffset, SymbolicAddress::NearbyIntD, ValType::F64);
       case Expr::F64Sin:
         return EmitUnaryMathBuiltinCall(f, exprOffset, SymbolicAddress::SinD, ValType::F64);
       case Expr::F64Cos:
@@ -3327,11 +3334,7 @@ EmitExpr(FunctionCompiler& f)
 
       // Future opcodes
       case Expr::F32CopySign:
-      case Expr::F32Trunc:
-      case Expr::F32Nearest:
       case Expr::F64CopySign:
-      case Expr::F64Nearest:
-      case Expr::F64Trunc:
       case Expr::I64Load8S:
       case Expr::I64Load16S:
       case Expr::I64Load32S:
diff --git a/js/src/asmjs/WasmTypes.cpp b/js/src/asmjs/WasmTypes.cpp
index 33271034ccd0..7ff99f5d49d7 100644
--- a/js/src/asmjs/WasmTypes.cpp
+++ b/js/src/asmjs/WasmTypes.cpp
@@ -305,6 +305,14 @@ wasm::AddressOf(SymbolicAddress imm, ExclusiveContext* cx)
         return FuncCast<double (double)>(fdlibm::floor, Args_Double_Double);
       case SymbolicAddress::FloorF:
         return FuncCast<float (float)>(fdlibm::floorf, Args_Float32_Float32);
+      case SymbolicAddress::TruncD:
+        return FuncCast<double (double)>(fdlibm::trunc, Args_Double_Double);
+      case SymbolicAddress::TruncF:
+        return FuncCast<float (float)>(fdlibm::truncf, Args_Float32_Float32);
+      case SymbolicAddress::NearbyIntD:
+        return FuncCast<double (double)>(nearbyint, Args_Double_Double);
+      case SymbolicAddress::NearbyIntF:
+        return FuncCast<float (float)>(nearbyintf, Args_Float32_Float32);
       case SymbolicAddress::ExpD:
         return FuncCast<double (double)>(fdlibm::exp, Args_Double_Double);
       case SymbolicAddress::LogD:
diff --git a/js/src/asmjs/WasmTypes.h b/js/src/asmjs/WasmTypes.h
index d08fe103756a..e16a066a3246 100644
--- a/js/src/asmjs/WasmTypes.h
+++ b/js/src/asmjs/WasmTypes.h
@@ -672,6 +672,10 @@ enum class SymbolicAddress
     CeilF,
     FloorD,
     FloorF,
+    TruncD,
+    TruncF,
+    NearbyIntD,
+    NearbyIntF,
     ExpD,
     LogD,
     PowD,