Revision: 6801
Author: [email protected]
Date: Tue Feb 15 13:11:31 2011
Log: Added gdb-jit interface support for ARM. Compressed .debug_line table
by 1)
removing duplicate adjacent entries having the same line number, and 2)
using
special opcodes to encode multiple machine register state changes in one
byte.
Also made a fix involving the order in which static initializers are
performed.
Patch by Shasank Chavan of Hewlett-Packard Development Company, LP
BUG=none
TEST=Try building for arm
Review URL: http://codereview.chromium.org/6524020
http://code.google.com/p/v8/source/detail?r=6801
Modified:
/branches/bleeding_edge/SConstruct
/branches/bleeding_edge/src/flag-definitions.h
/branches/bleeding_edge/src/gdb-jit.cc
=======================================
--- /branches/bleeding_edge/SConstruct Fri Feb 11 04:25:41 2011
+++ /branches/bleeding_edge/SConstruct Tue Feb 15 13:11:31 2011
@@ -890,7 +890,7 @@
return False
if env['os'] == 'win32' and env['library'] == 'shared' and env['prof']
== 'on':
Abort("Profiling on windows only supported for static library.")
- if env['gdbjit'] == 'on' and (env['os'] != 'linux' or
(env['arch'] != 'ia32' and env['arch'] != 'x64')):
+ if env['gdbjit'] == 'on' and (env['os'] != 'linux' or
(env['arch'] != 'ia32' and env['arch'] != 'x64' and env['arch'] != 'arm')):
Abort("GDBJIT interface is supported only for Intel-compatible (ia32
or x64) Linux target.")
if env['os'] == 'win32' and env['soname'] == 'on':
Abort("Shared Object soname not applicable for Windows.")
=======================================
--- /branches/bleeding_edge/src/flag-definitions.h Tue Feb 15 00:47:14 2011
+++ /branches/bleeding_edge/src/flag-definitions.h Tue Feb 15 13:11:31 2011
@@ -378,6 +378,7 @@
DEFINE_bool(gdbjit, false, "enable GDBJIT interface (disables compacting
GC)")
DEFINE_bool(gdbjit_full, false, "enable GDBJIT interface for all code
objects")
+DEFINE_bool(gdbjit_dump, false, "dump elf objects with debug info to disk")
//
// Debug only flags
=======================================
--- /branches/bleeding_edge/src/gdb-jit.cc Wed Feb 2 05:32:18 2011
+++ /branches/bleeding_edge/src/gdb-jit.cc Tue Feb 15 13:11:31 2011
@@ -395,7 +395,7 @@
void WriteHeader(Writer* w) {
ASSERT(w->position() == 0);
Writer::Slot<ELFHeader> header = w->CreateSlotHere<ELFHeader>();
-#if defined(V8_TARGET_ARCH_IA32)
+#if defined(V8_TARGET_ARCH_IA32) || defined(V8_TARGET_ARCH_ARM)
const uint8_t ident[16] =
{ 0x7f, 'E', 'L', 'F', 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0};
#elif defined(V8_TARGET_ARCH_X64)
@@ -413,6 +413,10 @@
// System V ABI, AMD64 Supplement
// http://www.x86-64.org/documentation/abi.pdf
header->machine = 62;
+#elif defined(V8_TARGET_ARCH_ARM)
+ // Set to EM_ARM, defined as 40, in "ARM ELF File Format" at
+ // infocenter.arm.com/help/topic/com.arm.doc.dui0101a/DUI0101A_Elf.pdf
+ header->machine = 40;
#else
#error Unsupported target architecture.
#endif
@@ -503,8 +507,7 @@
Binding binding() const {
return static_cast<Binding>(info >> 4);
}
-
-#if defined(V8_TARGET_ARCH_IA32)
+#if defined(V8_TARGET_ARCH_IA32) || defined(V8_TARGET_ARCH_ARM)
struct SerializedLayout {
SerializedLayout(uint32_t name,
uintptr_t value,
@@ -857,14 +860,20 @@
Writer::Slot<uint32_t> total_length = w->CreateSlotHere<uint32_t>();
uintptr_t start = w->position();
+ // Used for special opcodes
+ const int8_t line_base = 1;
+ const uint8_t line_range = 7;
+ const int8_t max_line_incr = (line_base + line_range - 1);
+ const uint8_t opcode_base = DW_LNS_NEGATE_STMT + 1;
+
w->Write<uint16_t>(2); // Field version.
Writer::Slot<uint32_t> prologue_length = w->CreateSlotHere<uint32_t>();
uintptr_t prologue_start = w->position();
w->Write<uint8_t>(1); // Field minimum_instruction_length.
w->Write<uint8_t>(1); // Field default_is_stmt.
- w->Write<int8_t>(0); // Field line_base.
- w->Write<uint8_t>(2); // Field line_range.
- w->Write<uint8_t>(DW_LNS_NEGATE_STMT + 1); // Field opcode_base.
+ w->Write<int8_t>(line_base); // Field line_base.
+ w->Write<uint8_t>(line_range); // Field line_range.
+ w->Write<uint8_t>(opcode_base); // Field opcode_base.
w->Write<uint8_t>(0); // DW_LNS_COPY operands count.
w->Write<uint8_t>(1); // DW_LNS_ADVANCE_PC operands count.
w->Write<uint8_t>(1); // DW_LNS_ADVANCE_LINE operands count.
@@ -881,6 +890,7 @@
WriteExtendedOpcode(w, DW_LNE_SET_ADDRESS, sizeof(intptr_t));
w->Write<intptr_t>(desc_->CodeStart());
+ w->Write<uint8_t>(DW_LNS_COPY);
intptr_t pc = 0;
intptr_t line = 1;
@@ -888,29 +898,66 @@
List<GDBJITLineInfo::PCInfo>* pc_info = desc_->lineinfo()->pc_info();
pc_info->Sort(&ComparePCInfo);
- for (int i = 0; i < pc_info->length(); i++) {
+
+ int pc_info_length = pc_info->length();
+ for (int i = 0; i < pc_info_length; i++) {
GDBJITLineInfo::PCInfo* info = &pc_info->at(i);
- uintptr_t pc_diff = info->pc_ - pc;
ASSERT(info->pc_ >= pc);
- if (pc_diff != 0) {
- w->Write<uint8_t>(DW_LNS_ADVANCE_PC);
- w->WriteSLEB128(pc_diff);
- pc += pc_diff;
- }
- intptr_t line_diff = desc_->GetScriptLineNumber(info->pos_) - line;
- if (line_diff != 0) {
- w->Write<uint8_t>(DW_LNS_ADVANCE_LINE);
- w->WriteSLEB128(line_diff);
- line += line_diff;
- }
- if (is_statement != info->is_statement_) {
+
+ // Reduce bloating in the debug line table by removing duplicate line
+ // entries (per DWARF2 standard).
+ intptr_t new_line = desc_->GetScriptLineNumber(info->pos_);
+ if (new_line == line) {
+ continue;
+ }
+
+ // Mark statement boundaries. For a better debugging experience,
mark
+ // the last pc address in the function as a statement (e.g. "}"), so
that
+ // a user can see the result of the last line executed in the
function,
+ // should control reach the end.
+ if ((i+1) == pc_info_length) {
+ if (!is_statement) {
+ w->Write<uint8_t>(DW_LNS_NEGATE_STMT);
+ }
+ } else if (is_statement != info->is_statement_) {
w->Write<uint8_t>(DW_LNS_NEGATE_STMT);
is_statement = !is_statement;
}
- if (pc_diff != 0 || i == 0) {
+
+ // Generate special opcodes, if possible. This results in more
compact
+ // debug line tables. See the DWARF 2.0 standard to learn more about
+ // special opcodes.
+ uintptr_t pc_diff = info->pc_ - pc;
+ intptr_t line_diff = new_line - line;
+
+ // Compute special opcode (see DWARF 2.0 standard)
+ intptr_t special_opcode = (line_diff - line_base) +
+ (line_range * pc_diff) + opcode_base;
+
+ // If special_opcode is less than or equal to 255, it can be used as
a
+ // special opcode. If line_diff is larger than the max line
increment
+ // allowed for a special opcode, or if line_diff is less than the
minimum
+ // line that can be added to the line register (i.e. line_base), then
+ // special_opcode can't be used.
+ if ((special_opcode >= opcode_base) && (special_opcode <= 255) &&
+ (line_diff <= max_line_incr) && (line_diff >= line_base)) {
+ w->Write<uint8_t>(special_opcode);
+ } else {
+ w->Write<uint8_t>(DW_LNS_ADVANCE_PC);
+ w->WriteSLEB128(pc_diff);
+ w->Write<uint8_t>(DW_LNS_ADVANCE_LINE);
+ w->WriteSLEB128(line_diff);
w->Write<uint8_t>(DW_LNS_COPY);
}
- }
+
+ // Increment the pc and line operands.
+ pc += pc_diff;
+ line += line_diff;
+ }
+ // Advance the pc to the end of the routine, since the end sequence
opcode
+ // requires this.
+ w->Write<uint8_t>(DW_LNS_ADVANCE_PC);
+ w->WriteSLEB128(desc_->CodeSize() - pc);
WriteExtendedOpcode(w, DW_LNE_END_SEQUENCE, 0);
total_length.set(static_cast<uint32_t>(w->position() - start));
return true;
@@ -1237,6 +1284,20 @@
static void RegisterCodeEntry(JITCodeEntry* entry) {
+#if defined(DEBUG) && !defined(WIN32)
+ static int file_num = 0;
+ if (FLAG_gdbjit_dump) {
+ static const int kMaxFileNameSize = 64;
+ static const char* kElfFilePrefix = "/tmp/elfdump";
+ static const char* kObjFileExt = ".o";
+ char file_name[64];
+
+ OS::SNPrintF(Vector<char>(file_name, kMaxFileNameSize), "%s%d%s",
+ kElfFilePrefix, file_num++, kObjFileExt);
+ WriteBytes(file_name, entry->symfile_addr_, entry->symfile_size_);
+ }
+#endif
+
entry->next_ = __jit_debug_descriptor.first_entry_;
if (entry->next_ != NULL) entry->next_->prev_ = entry;
__jit_debug_descriptor.first_entry_ =
@@ -1294,7 +1355,13 @@
}
-static HashMap entries(&SameCodeObjects);
+static HashMap* GetEntries() {
+ static HashMap* entries = NULL;
+ if (entries == NULL) {
+ entries = new HashMap(&SameCodeObjects);
+ }
+ return entries;
+}
static uint32_t HashForCodeObject(Code* code) {
@@ -1398,7 +1465,7 @@
if (!FLAG_gdbjit) return;
AssertNoAllocation no_gc;
- HashMap::Entry* e = entries.Lookup(code, HashForCodeObject(code), true);
+ HashMap::Entry* e = GetEntries()->Lookup(code, HashForCodeObject(code),
true);
if (e->value != NULL && !IsLineInfoTagged(e->value)) return;
GDBJITLineInfo* lineinfo = UntagLineInfo(e->value);
@@ -1411,7 +1478,7 @@
if (!FLAG_gdbjit_full && !code_desc.IsLineInfoAvailable()) {
delete lineinfo;
- entries.Remove(code, HashForCodeObject(code));
+ GetEntries()->Remove(code, HashForCodeObject(code));
return;
}
@@ -1464,7 +1531,9 @@
void GDBJITInterface::RemoveCode(Code* code) {
if (!FLAG_gdbjit) return;
- HashMap::Entry* e = entries.Lookup(code, HashForCodeObject(code), false);
+ HashMap::Entry* e = GetEntries()->Lookup(code,
+ HashForCodeObject(code),
+ false);
if (e == NULL) return;
if (IsLineInfoTagged(e->value)) {
@@ -1475,14 +1544,14 @@
DestroyCodeEntry(entry);
}
e->value = NULL;
- entries.Remove(code, HashForCodeObject(code));
+ GetEntries()->Remove(code, HashForCodeObject(code));
}
void GDBJITInterface::RegisterDetailedLineInfo(Code* code,
GDBJITLineInfo* line_info) {
ASSERT(!IsLineInfoTagged(line_info));
- HashMap::Entry* e = entries.Lookup(code, HashForCodeObject(code), true);
+ HashMap::Entry* e = GetEntries()->Lookup(code, HashForCodeObject(code),
true);
ASSERT(e->value == NULL);
e->value = TagLineInfo(line_info);
}
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