Add CODE_POINTER_ALIGN, use it in Page to align generated code.

src/globals.h

 // Copyright 2006-2009 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 196 matching lines @@
 
 // Desired alignment for maps.
 #if V8_HOST_ARCH_64_BIT
 const intptr_t kMapAlignmentBits = kObjectAlignmentBits;
 #else
 const intptr_t kMapAlignmentBits = kObjectAlignmentBits + 3;
 #endif
 const intptr_t kMapAlignment = (1 << kMapAlignmentBits);
 const intptr_t kMapAlignmentMask = kMapAlignment - 1;
 
+// Desired alignment for generated code.
+// Code entry points are aligned to 32 bytes (cache line size in some CPUs).

[Vitaly Repeshko, 2010/09/24 15:45:38]

In most of the CPUs we deal with it's actually 64. Please change the
parenthetical remark to "to improve cache line utilization".

+const int kCodeAlignmentBits = 5;
+const intptr_t kCodeAlignment = 1 << kCodeAlignmentBits;
+const intptr_t kCodeAlignmentMask = kCodeAlignment - 1;
+
 // Tag information for Failure.
 const int kFailureTag = 3;
 const int kFailureTagSize = 2;
 const intptr_t kFailureTagMask = (1 << kFailureTagSize) - 1;
 
 
 const int kBitsPerByte = 8;
 const int kBitsPerByteLog2 = 3;
 const int kBitsPerPointer = kPointerSize * kBitsPerByte;
 const int kBitsPerInt = kIntSize * kBitsPerByte;
@@ skipping 354 matching lines @@
   (((value) + kObjectAlignmentMask) & ~kObjectAlignmentMask)
 
 // POINTER_SIZE_ALIGN returns the value aligned as a pointer.
 #define POINTER_SIZE_ALIGN(value)                               \
   (((value) + kPointerAlignmentMask) & ~kPointerAlignmentMask)
 
 // MAP_POINTER_ALIGN returns the value aligned as a map pointer.
 #define MAP_POINTER_ALIGN(value)                                \
   (((value) + kMapAlignmentMask) & ~kMapAlignmentMask)
 
+// CODE_POINTER_ALIGN returns the value aligned as a generated code segment.
+#define CODE_POINTER_ALIGN(value)                               \
+  (((value) + kCodeAlignmentMask) & ~kCodeAlignmentMask)
+
 // The expression OFFSET_OF(type, field) computes the byte-offset
 // of the specified field relative to the containing type. This
 // corresponds to 'offsetof' (in stddef.h), except that it doesn't
 // use 0 or NULL, which causes a problem with the compiler warnings
 // we have enabled (which is also why 'offsetof' doesn't seem to work).
 // Here we simply use the non-zero value 4, which seems to work.
 #define OFFSET_OF(type, field)                                          \
   (reinterpret_cast<intptr_t>(&(reinterpret_cast<type*>(4)->field)) - 4)
 
 
@@ skipping 97 matching lines @@
                   CMOV = 15,   // x86
                   RDTSC = 4,   // x86
                   CPUID = 10,  // x86
                   VFP3 = 1,    // ARM
                   ARMv7 = 2,   // ARM
                   SAHF = 0};   // x86
 
 } }  // namespace v8::internal
 
 #endif  // V8_GLOBALS_H_