Use the "enum hack" to fix the SmiTagging constants.

The "enum hack" (see Item 2 of "Effective C++") is the only known
portable way to define constant integral values within template
classes. Fixes the weird work-arounds required for certain GCC
versions.

R=jarin@chromium.org, rossberg@chromium.org

Review URL: https://codereview.chromium.org/527603002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@23550 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

include/v8.h

@@ -5606,8 +5606,9 @@ V8_INLINE internal::Object* IntToSmi(int value) {
 
 // Smi constants for 32-bit systems.
 template <> struct SmiTagging<4> {
-  static const int kSmiShiftSize = 0;
-  static const int kSmiValueSize = 31;
+  enum { kSmiShiftSize = 0, kSmiValueSize = 31 };
+  static int SmiShiftSize() { return kSmiShiftSize; }
+  static int SmiValueSize() { return kSmiValueSize; }
   V8_INLINE static int SmiToInt(const internal::Object* value) {
     int shift_bits = kSmiTagSize + kSmiShiftSize;
     // Throw away top 32 bits and shift down (requires >> to be sign extending).
@@ -5634,8 +5635,9 @@ template <> struct SmiTagging<4> {
 
 // Smi constants for 64-bit systems.
 template <> struct SmiTagging<8> {
-  static const int kSmiShiftSize = 31;
-  static const int kSmiValueSize = 32;
+  enum { kSmiShiftSize = 31, kSmiValueSize = 32 };
+  static int SmiShiftSize() { return kSmiShiftSize; }
+  static int SmiValueSize() { return kSmiValueSize; }
   V8_INLINE static int SmiToInt(const internal::Object* value) {
     int shift_bits = kSmiTagSize + kSmiShiftSize;
     // Shift down and throw away top 32 bits.

src/compiler/change-lowering.cc

@@ -50,28 +50,16 @@ Node* ChangeLowering::HeapNumberValueIndexConstant() {
 
 
 Node* ChangeLowering::SmiMaxValueConstant() {
-  // TODO(turbofan): Work-around for weird GCC 4.6 linker issue:
-  // src/compiler/change-lowering.cc:46: undefined reference to
-  // `v8::internal::SmiTagging<4u>::kSmiValueSize'
-  // src/compiler/change-lowering.cc:46: undefined reference to
-  // `v8::internal::SmiTagging<8u>::kSmiValueSize'
-  STATIC_ASSERT(SmiTagging<4>::kSmiValueSize == 31);
-  STATIC_ASSERT(SmiTagging<8>::kSmiValueSize == 32);
-  const int smi_value_size = machine()->is64() ? 32 : 31;
+  const int smi_value_size = machine()->is32() ? SmiTagging<4>::SmiValueSize()
+                                               : SmiTagging<8>::SmiValueSize();
   return jsgraph()->Int32Constant(
       -(static_cast<int>(0xffffffffu << (smi_value_size - 1)) + 1));
 }
 
 
 Node* ChangeLowering::SmiShiftBitsConstant() {
-  // TODO(turbofan): Work-around for weird GCC 4.6 linker issue:
-  // src/compiler/change-lowering.cc:46: undefined reference to
-  // `v8::internal::SmiTagging<4u>::kSmiShiftSize'
-  // src/compiler/change-lowering.cc:46: undefined reference to
-  // `v8::internal::SmiTagging<8u>::kSmiShiftSize'
-  STATIC_ASSERT(SmiTagging<4>::kSmiShiftSize == 0);
-  STATIC_ASSERT(SmiTagging<8>::kSmiShiftSize == 31);
-  const int smi_shift_size = machine()->is64() ? 31 : 0;
+  const int smi_shift_size = machine()->is32() ? SmiTagging<4>::SmiShiftSize()
+                                               : SmiTagging<8>::SmiShiftSize();
   return jsgraph()->Int32Constant(smi_shift_size + kSmiTagSize);
 }
 

test/compiler-unittests/change-lowering-unittest.cc

@@ -59,24 +59,12 @@ class ChangeLoweringTest : public GraphTest {
   }
   int SmiShiftAmount() const { return kSmiTagSize + SmiShiftSize(); }
   int SmiShiftSize() const {
-    // TODO(turbofan): Work-around for weird GCC 4.6 linker issue:
-    // src/compiler/change-lowering.cc:46: undefined reference to
-    // `v8::internal::SmiTagging<4u>::kSmiShiftSize'
-    // src/compiler/change-lowering.cc:46: undefined reference to
-    // `v8::internal::SmiTagging<8u>::kSmiShiftSize'
-    STATIC_ASSERT(SmiTagging<4>::kSmiShiftSize == 0);
-    STATIC_ASSERT(SmiTagging<8>::kSmiShiftSize == 31);
-    return Is32() ? 0 : 31;
+    return Is32() ? SmiTagging<4>::SmiShiftSize()
+                  : SmiTagging<8>::SmiShiftSize();
   }
   int SmiValueSize() const {
-    // TODO(turbofan): Work-around for weird GCC 4.6 linker issue:
-    // src/compiler/change-lowering.cc:46: undefined reference to
-    // `v8::internal::SmiTagging<4u>::kSmiValueSize'
-    // src/compiler/change-lowering.cc:46: undefined reference to
-    // `v8::internal::SmiTagging<8u>::kSmiValueSize'
-    STATIC_ASSERT(SmiTagging<4>::kSmiValueSize == 31);
-    STATIC_ASSERT(SmiTagging<8>::kSmiValueSize == 32);
-    return Is32() ? 31 : 32;
+    return Is32() ? SmiTagging<4>::SmiValueSize()
+                  : SmiTagging<8>::SmiValueSize();
   }
 
   Node* Parameter(int32_t index = 0) {