[wasm] Fix I32ReinterpretF32 and I64ReinterpretF64 on ia32.

src/wasm/function-body-decoder.h

 // Copyright 2015 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_WASM_FUNCTION_BODY_DECODER_H_
 #define V8_WASM_FUNCTION_BODY_DECODER_H_
 
 #include <iterator>
 
 #include "src/base/compiler-specific.h"
@@ skipping 52 matching lines @@
   unsigned length;
   inline ImmI64Operand(Decoder* decoder, const byte* pc) {
     value = decoder->checked_read_i64v(pc, 1, &length, "immi64");
   }
 };
 
 struct ImmF32Operand {
   float value;
   unsigned length;
   inline ImmF32Operand(Decoder* decoder, const byte* pc) {
-    value = bit_cast<float>(decoder->checked_read_u32(pc, 1, "immf32"));
+    // Avoid bit_cast because it might not preserve the signalling bit of a NaN.
+    uint32_t tmp = decoder->checked_read_u32(pc, 1, "immf32");
+    memcpy(&value, &tmp, sizeof(value));
     length = 4;
   }
 };
 
 struct ImmF64Operand {
   double value;
   unsigned length;
   inline ImmF64Operand(Decoder* decoder, const byte* pc) {
-    value = bit_cast<double>(decoder->checked_read_u64(pc, 1, "immf64"));
+    // Avoid bit_cast because it might not preserve the signalling bit of a NaN.
+    uint64_t tmp = decoder->checked_read_u64(pc, 1, "immf64");
+    memcpy(&value, &tmp, sizeof(value));
     length = 8;
   }
 };
 
 struct GlobalIndexOperand {
   uint32_t index;
   ValueType type;
   const WasmGlobal* global;
   unsigned length;
 
@@ skipping 371 matching lines @@
   }
 
   bool has_next() { return pc_ < end_; }
 };
 
 }  // namespace wasm
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_WASM_FUNCTION_BODY_DECODER_H_