MIPS: Fix unaligned read/write operations in wasm.

TEST=cctest/test-run-wasm/*, cctest/test-run-wasm-module/*, unittests
BUG=

Review URL: https://codereview.chromium.org/1581223002

Cr-Commit-Position: refs/heads/master@{#33678}

src/utils.h

@@ -1715,75 +1715,47 @@ inline uintptr_t GetCurrentStackPosition() {
   return limit;
 }
 
-static inline double ReadDoubleValue(const void* p) {
-#ifndef V8_TARGET_ARCH_MIPS
-  return *reinterpret_cast<const double*>(p);
+template <typename V>
+static inline V ReadUnalignedValue(const void* p) {
+#if !(V8_TARGET_ARCH_MIPS || V8_TARGET_ARCH_MIPS64)
+  return *reinterpret_cast<const V*>(p);
+#else
+  V r;
+  memmove(&r, p, sizeof(V));
+  return r;
+#endif  // V8_TARGET_ARCH_MIPS || V8_TARGET_ARCH_MIPS64
+}
+
+template <typename V>
+static inline void WriteUnalignedValue(void* p, V value) {
+#if !(V8_TARGET_ARCH_MIPS || V8_TARGET_ARCH_MIPS64)
+  *(reinterpret_cast<V*>(p)) = value;
 #else   // V8_TARGET_ARCH_MIPS
-  // Prevent compiler from using load-double (mips ldc1) on (possibly)
-  // non-64-bit aligned address.
-  union conversion {
-    double d;
-    uint32_t u[2];
-  } c;
-  const uint32_t* ptr = reinterpret_cast<const uint32_t*>(p);
-  c.u[0] = *ptr;
-  c.u[1] = *(ptr + 1);
-  return c.d;
-#endif  // V8_TARGET_ARCH_MIPS
+  memmove(p, &value, sizeof(V));
+#endif  // V8_TARGET_ARCH_MIPS || V8_TARGET_ARCH_MIPS64
+}
+
+static inline double ReadDoubleValue(const void* p) {
+  return ReadUnalignedValue<double>(p);
 }
 
 
 static inline void WriteDoubleValue(void* p, double value) {
-#ifndef V8_TARGET_ARCH_MIPS
-  *(reinterpret_cast<double*>(p)) = value;
-#else   // V8_TARGET_ARCH_MIPS
-  // Prevent compiler from using load-double (mips sdc1) on (possibly)
-  // non-64-bit aligned address.
-  union conversion {
-    double d;
-    uint32_t u[2];
-  } c;
-  c.d = value;
-  uint32_t* ptr = reinterpret_cast<uint32_t*>(p);
-  *ptr = c.u[0];
-  *(ptr + 1) = c.u[1];
-#endif  // V8_TARGET_ARCH_MIPS
+  WriteUnalignedValue(p, value);
 }
 
 
 static inline uint16_t ReadUnalignedUInt16(const void* p) {
-#if !(V8_TARGET_ARCH_MIPS || V8_TARGET_ARCH_MIPS64)
-  return *reinterpret_cast<const uint16_t*>(p);
-#else   // V8_TARGET_ARCH_MIPS || V8_TARGET_ARCH_MIPS64
-  // Prevent compiler from using load-half (mips lh) on (possibly)
-  // non-16-bit aligned address.
-  union conversion {
-    uint16_t h;
-    uint8_t b[2];
-  } c;
-  const uint8_t* ptr = reinterpret_cast<const uint8_t*>(p);
-  c.b[0] = *ptr;
-  c.b[1] = *(ptr + 1);
-  return c.h;
-#endif  // V8_TARGET_ARCH_MIPS || V8_TARGET_ARCH_MIPS64
+  return ReadUnalignedValue<uint16_t>(p);
 }
 
 
 static inline void WriteUnalignedUInt16(void* p, uint16_t value) {
-#if !(V8_TARGET_ARCH_MIPS || V8_TARGET_ARCH_MIPS64)
-  *(reinterpret_cast<uint16_t*>(p)) = value;
-#else   // V8_TARGET_ARCH_MIPS || V8_TARGET_ARCH_MIPS64
-  // Prevent compiler from using store-half (mips sh) on (possibly)
-  // non-16-bit aligned address.
-  union conversion {
-    uint16_t h;
-    uint8_t b[2];
-  } c;
-  c.h = value;
-  uint8_t* ptr = reinterpret_cast<uint8_t*>(p);
-  *ptr = c.b[0];
-  *(ptr + 1) = c.b[1];
-#endif  // V8_TARGET_ARCH_MIPS || V8_TARGET_ARCH_MIPS64
+  WriteUnalignedValue(p, value);
+}
+
+static inline void WriteUnalignedUInt32(void* p, uint32_t value) {
+  WriteUnalignedValue(p, value);
 }
 
 }  // namespace internal

src/wasm/encoder.cc

@@ -30,13 +30,13 @@ void EmitUint8(byte** b, uint8_t x) {
 
 
 void EmitUint16(byte** b, uint16_t x) {
-  Memory::uint16_at(*b) = x;
+  WriteUnalignedUInt16(*b, x);
   *b += 2;
 }
 
 
 void EmitUint32(byte** b, uint32_t x) {
-  Memory::uint32_at(*b) = x;
+  WriteUnalignedUInt32(*b, x);
   *b += 4;
 }
 

test/cctest/wasm/wasm-run-utils.h

@@ -196,7 +196,7 @@ class TestingModule : public ModuleEnv {
  private:
   WasmModuleInstance instance_;
   uint32_t global_offset;
-  byte global_data[kMaxGlobalsSize];  // preallocated global data.
+  V8_ALIGNED(8) byte global_data[kMaxGlobalsSize];  // preallocated global data.
 
   WasmGlobal* AddGlobal(MachineType mem_type) {
     AllocModule();