Revision: 5526
Author: [email protected]
Date: Fri Sep 24 14:48:44 2010
Log: Add CODE_POINTER_ALIGN, use it in Page to align generated code.
The object's space in Page starts after Page header and is aligned to
kMapAlignment which is 32 bytes on 32-bit and 8 bytes on 64-bit.
In case of 64-bit target, the current page header size is exactly 32 bytes
so we get the code magically aligned at 32 bytes but it is better to have a
separate CODE_POINTER_ALIGN macro to make sure the object space in Page is
aligned properly for both maps and code.
There could be a small waste of bytes sometimes (since both Page header and
Code header sizes are aligned separately) but it seems the optimal one
would involve cross-dependencies between .h files and not clear if it's
worth it.
This is a back-port from Isolates branch.
Review URL: http://codereview.chromium.org/3461021
http://code.google.com/p/v8/source/detail?r=5526
Modified:
/branches/bleeding_edge/src/globals.h
/branches/bleeding_edge/src/heap.cc
/branches/bleeding_edge/src/objects-debug.cc
/branches/bleeding_edge/src/objects.h
/branches/bleeding_edge/src/spaces.h
=======================================
--- /branches/bleeding_edge/src/globals.h Tue Aug 31 01:05:42 2010
+++ /branches/bleeding_edge/src/globals.h Fri Sep 24 14:48:44 2010
@@ -214,6 +214,12 @@
const intptr_t kMapAlignment = (1 << kMapAlignmentBits);
const intptr_t kMapAlignmentMask = kMapAlignment - 1;
+// Desired alignment for generated code is 32 bytes (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;
@@ -588,6 +594,10 @@
#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
=======================================
--- /branches/bleeding_edge/src/heap.cc Fri Sep 24 04:45:12 2010
+++ /branches/bleeding_edge/src/heap.cc Fri Sep 24 14:48:44 2010
@@ -2444,7 +2444,7 @@
// Compute size
int body_size = RoundUp(desc.instr_size, kObjectAlignment);
int obj_size = Code::SizeFor(body_size);
- ASSERT(IsAligned(obj_size, Code::kCodeAlignment));
+ ASSERT(IsAligned(static_cast<intptr_t>(obj_size), kCodeAlignment));
Object* result;
if (obj_size > MaxObjectSizeInPagedSpace()) {
result = lo_space_->AllocateRawCode(obj_size);
=======================================
--- /branches/bleeding_edge/src/objects-debug.cc Fri Sep 24 01:18:33 2010
+++ /branches/bleeding_edge/src/objects-debug.cc Fri Sep 24 14:48:44 2010
@@ -905,7 +905,7 @@
void Code::CodeVerify() {
CHECK(IsAligned(reinterpret_cast<intptr_t>(instruction_start()),
- static_cast<intptr_t>(kCodeAlignment)));
+ kCodeAlignment));
Address last_gc_pc = NULL;
for (RelocIterator it(this); !it.done(); it.next()) {
it.rinfo()->Verify();
=======================================
--- /branches/bleeding_edge/src/objects.h Fri Sep 24 01:18:33 2010
+++ /branches/bleeding_edge/src/objects.h Fri Sep 24 14:48:44 2010
@@ -3013,11 +3013,6 @@
void CodePrint();
void CodeVerify();
#endif
- // Code entry points are aligned to 32 bytes.
- static const int kCodeAlignmentBits = 5;
- static const int kCodeAlignment = 1 << kCodeAlignmentBits;
- static const int kCodeAlignmentMask = kCodeAlignment - 1;
-
// Layout description.
static const int kInstructionSizeOffset = HeapObject::kHeaderSize;
static const int kRelocationInfoOffset = kInstructionSizeOffset +
kIntSize;
@@ -3026,8 +3021,7 @@
// Add padding to align the instruction start following right after
// the Code object header.
static const int kHeaderSize =
- (kKindSpecificFlagsOffset + kIntSize + kCodeAlignmentMask) &
- ~kCodeAlignmentMask;
+ CODE_POINTER_ALIGN(kKindSpecificFlagsOffset + kIntSize);
// Byte offsets within kKindSpecificFlagsOffset.
static const int kStubMajorKeyOffset = kKindSpecificFlagsOffset + 1;
=======================================
--- /branches/bleeding_edge/src/spaces.h Fri Sep 3 05:00:05 2010
+++ /branches/bleeding_edge/src/spaces.h Fri Sep 24 14:48:44 2010
@@ -243,8 +243,10 @@
static const int kPageHeaderSize = kPointerSize + kPointerSize +
kIntSize +
kIntSize + kPointerSize;
- // The start offset of the object area in a page.
- static const int kObjectStartOffset = MAP_POINTER_ALIGN(kPageHeaderSize);
+ // The start offset of the object area in a page. Aligned to both maps
and
+ // code alignment to be suitable for both.
+ static const int kObjectStartOffset =
+ CODE_POINTER_ALIGN(MAP_POINTER_ALIGN(kPageHeaderSize));
// Object area size in bytes.
static const int kObjectAreaSize = kPageSize - kObjectStartOffset;
--
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