MIPS: Fix unaligned address of double.

src/deoptimizer.h

Index: src/deoptimizer.h
diff --git a/src/deoptimizer.h b/src/deoptimizer.h
index edf6c504f1c1340ae9345dd510a7dbc8c34d5f11..2ce4fd2c2d1777a547e15e939b48629fe9d23d9b 100644
--- a/src/deoptimizer.h
+++ b/src/deoptimizer.h
@@ -38,6 +38,22 @@
 namespace v8 {
 namespace internal {
 

[Jakob Kummerow, 2013/05/10 10:06:28]

nit: two empty newlines between top-level things, please.

[palfia, 2013/05/17 17:24:32]

Done.

+// Prevent gcc from using load-double (mips ldc1) on (possibly)
+// non-64-bit aligned address.
+static inline double read_double_value(Address p) {
+#ifndef V8_TARGET_ARCH_MIPS

[danno, 2013/05/10 10:15:55]

I think it's better to use the platform independent V8_HOST_CAN_READ_UNALIGNED
rather than make this MIPS-specific

[palfia, 2013/05/17 17:24:32]

Done.

+  return Memory::double_at(p)
+#else  // V8_TARGET_ARCH_MIPS
+  union conversion {
+    double d;
+    uint32_t u[2];
+  } c;

[danno, 2013/05/10 10:15:55]

And if you do that, you will need to make sure that endianess works correctly,
something like:
uint64_t data = *reinterpret_cast<uint64_t*>(p);
return BitCast<double>(data);

+  c.u[0] = (*reinterpret_cast<uint32_t*>(p));

[Jakob Kummerow, 2013/05/10 10:06:28]

nit: don't need the outer parentheses.

[palfia, 2013/05/17 17:24:32]

Done.

+  c.u[1] = (*reinterpret_cast<uint32_t*>(p + 4));
+  return c.d;
+#endif  // V8_TARGET_ARCH_MIPS
+}
+
 class FrameDescription;
 class TranslationIterator;
 class DeoptimizingCodeListNode;
@@ -492,19 +508,7 @@ class FrameDescription {
 
   double GetDoubleFrameSlot(unsigned offset) {
     intptr_t* ptr = GetFrameSlotPointer(offset);
-#if V8_TARGET_ARCH_MIPS
-    // Prevent gcc from using load-double (mips ldc1) on (possibly)
-    // non-64-bit aligned double. Uses two lwc1 instructions.
-    union conversion {
-      double d;
-      uint32_t u[2];
-    } c;
-    c.u[0] = *reinterpret_cast<uint32_t*>(ptr);
-    c.u[1] = *(reinterpret_cast<uint32_t*>(ptr) + 1);
-    return c.d;
-#else
-    return *reinterpret_cast<double*>(ptr);
-#endif
+    return read_double_value(reinterpret_cast<Address>(ptr));
   }
 
   void SetFrameSlot(unsigned offset, intptr_t value) {
@@ -800,7 +804,7 @@ class SlotRef BASE_EMBEDDED {
       }
 
       case DOUBLE: {
-        double value = Memory::double_at(addr_);
+        double value = read_double_value(addr_);
         return isolate->factory()->NewNumber(value);
       }