Skip to content

V
V8
Commit 65821f32 authored by kmillikin@chromium.org's avatar kmillikin@chromium.org
Browse files
Options

Rename member variables and functions and clarify comments to try to 

make the operation of LabelShadows more understandable.
Review URL: http://codereview.chromium.org/7868

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@556 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
parent b3389670
Hide whitespace changes
Inline Side-by-side
Showing with 87 additions and 52 deletions
src/assembler.h
View file @ 65821f32
......@@ -48,7 +48,7 @@ namespace v8 { namespace internal {
// unknown pc location. Assembler::bind() is used to bind a label to the
// current pc. A label can be bound only once.
class Label : public ZoneObject { // ShadowLables are dynamically allocated.
class Label : public ZoneObject { // LabelShadows are dynamically allocated.
public:
INLINE(Label()) { Unuse(); }
INLINE(~Label()) { ASSERT(!is_linked()); }
......@@ -87,17 +87,19 @@ class Label : public ZoneObject { // ShadowLables are dynamically allocated.
};
// A LabelShadow is a label that temporarily shadows another label. It
// is used to catch linking and binding of labels in certain scopes,
// e.g. try blocks. LabelShadows are themselves labels which can be
// used (only) after they are not shadowing anymore.
class LabelShadow: public Label {
// A LabelShadow represents a label that is temporarily shadowed by another
// label (represented by the original label during shadowing). They are used
// to catch jumps to labels in certain contexts, e.g. try blocks. After
// shadowing ends, the formerly shadowed label is again represented by the
// original label and the LabelShadow can be used as a label in its own
// right, representing the formerly shadowing label.
class LabelShadow : public Label {
public:
explicit LabelShadow(Label* shadowed) {
ASSERT(shadowed != NULL);
shadowed_ = shadowed;
shadowed_pos_ = shadowed->pos_;
shadowed->Unuse();
explicit LabelShadow(Label* original) {
ASSERT(original != NULL);
original_label_ = original;
original_pos_ = original->pos_;
original->Unuse();
#ifdef DEBUG
is_shadowing_ = true;
#endif
......@@ -109,18 +111,23 @@ class LabelShadow: public Label {
void StopShadowing() {
ASSERT(is_shadowing_ && is_unused());
pos_ = shadowed_->pos_;
shadowed_->pos_ = shadowed_pos_;
pos_ = original_label_->pos_;
original_label_->pos_ = original_pos_;
#ifdef DEBUG
is_shadowing_ = false;
#endif
}
Label* shadowed() const { return shadowed_; }
Label* original_label() const { return original_label_; }
private:
Label* shadowed_;
int shadowed_pos_;
// During shadowing, the currently shadowing label. After shadowing, the
// label that was shadowed.
Label* original_label_;
// During shadowing, the saved state of the original label.
int original_pos_;
#ifdef DEBUG
bool is_shadowing_;
#endif
......
src/codegen-arm.cc
View file @ 65821f32
......@@ -1634,9 +1634,13 @@ void CodeGenerator::VisitTryCatch(TryCatch* node) {
__ PushTryHandler(IN_JAVASCRIPT, TRY_CATCH_HANDLER);
// Introduce shadow labels for all escapes from the try block,
// including returns. We should probably try to unify the escaping
// labels and the return label.
// Shadow the labels for all escapes from the try block, including
// returns. During shadowing, the original label is hidden as the
// LabelShadow and operations on the original actually affect the
// shadowing label.
//
// We should probably try to unify the escaping labels and the return
// label.
int nof_escapes = node->escaping_labels()->length();
List<LabelShadow*> shadows(1 + nof_escapes);
shadows.Add(new LabelShadow(&function_return_));
......@@ -1649,6 +1653,8 @@ void CodeGenerator::VisitTryCatch(TryCatch* node) {
__ pop(r0); // Discard the result.
// Stop the introduced shadowing and count the number of required unlinks.
// After shadowing stops, the original labels are unshadowed and the
// LabelShadows represent the formerly shadowing labels.
int nof_unlinks = 0;
for (int i = 0; i <= nof_escapes; i++) {
shadows[i]->StopShadowing();
......@@ -1667,7 +1673,8 @@ void CodeGenerator::VisitTryCatch(TryCatch* node) {
// Code slot popped.
if (nof_unlinks > 0) __ b(&exit);
// Generate unlink code for all used shadow labels.
// Generate unlink code for the (formerly) shadowing labels that have been
// jumped to.
for (int i = 0; i <= nof_escapes; i++) {
if (shadows[i]->is_linked()) {
// Unlink from try chain;
......@@ -1684,7 +1691,7 @@ void CodeGenerator::VisitTryCatch(TryCatch* node) {
__ add(sp, sp, Operand(StackHandlerConstants::kSize - kPointerSize));
// Code slot popped.
__ b(shadows[i]->shadowed());
__ b(shadows[i]->original_label());
}
}
......@@ -1715,9 +1722,12 @@ void CodeGenerator::VisitTryFinally(TryFinally* node) {
__ PushTryHandler(IN_JAVASCRIPT, TRY_FINALLY_HANDLER);
// Introduce shadow labels for all escapes from the try block,
// including returns. We should probably try to unify the escaping
// labels and the return label.
// Shadow the labels for all escapes from the try block, including
// returns. Shadowing hides the original label as the LabelShadow and
// operations on the original actually affect the shadowing label.
//
// We should probably try to unify the escaping labels and the return
// label.
int nof_escapes = node->escaping_labels()->length();
List<LabelShadow*> shadows(1 + nof_escapes);
shadows.Add(new LabelShadow(&function_return_));
......@@ -1728,8 +1738,9 @@ void CodeGenerator::VisitTryFinally(TryFinally* node) {
// Generate code for the statements in the try block.
VisitStatements(node->try_block()->statements());
// Stop the introduced shadowing and count the number of required
// unlinks.
// Stop the introduced shadowing and count the number of required unlinks.
// After shadowing stops, the original labels are unshadowed and the
// LabelShadows represent the formerly shadowing labels.
int nof_unlinks = 0;
for (int i = 0; i <= nof_escapes; i++) {
shadows[i]->StopShadowing();
......@@ -1742,14 +1753,17 @@ void CodeGenerator::VisitTryFinally(TryFinally* node) {
__ mov(r2, Operand(Smi::FromInt(FALLING)));
if (nof_unlinks > 0) __ b(&unlink);
// Generate code that sets the state for all used shadow labels.
// Generate code to set the state for the (formerly) shadowing labels that
// have been jumped to.
for (int i = 0; i <= nof_escapes; i++) {
if (shadows[i]->is_linked()) {
__ bind(shadows[i]);
if (shadows[i]->shadowed() == &function_return_) {
__ push(r0); // Materialize the return value on the stack
if (shadows[i]->original_label() == &function_return_) {
// If this label shadowed the function return, materialize the
// return value on the stack.
__ push(r0);
} else {
// Fake TOS for break and continue (not return).
// Fake TOS for labels that shadowed breaks and continues.
__ mov(r0, Operand(Factory::undefined_value()));
__ push(r0);
}
......@@ -1796,18 +1810,18 @@ void CodeGenerator::VisitTryFinally(TryFinally* node) {
__ pop(r0);
break_stack_height_ -= kFinallyStackSize;
// Generate code that jumps to the right destination for all used
// shadow labels.
// Generate code to jump to the right destination for all used (formerly)
// shadowing labels.
for (int i = 0; i <= nof_escapes; i++) {
if (shadows[i]->is_bound()) {
__ cmp(r2, Operand(Smi::FromInt(JUMPING + i)));
if (shadows[i]->shadowed() != &function_return_) {
if (shadows[i]->original_label() != &function_return_) {
Label next;
__ b(ne, &next);
__ b(shadows[i]->shadowed());
__ b(shadows[i]->original_label());
__ bind(&next);
} else {
__ b(eq, shadows[i]->shadowed());
__ b(eq, shadows[i]->original_label());
}
}
}
......
src/codegen-ia32.cc
View file @ 65821f32
......@@ -2000,9 +2000,13 @@ void CodeGenerator::VisitTryCatch(TryCatch* node) {
// TODO(1222589): remove the reliance of PushTryHandler on a cached TOS
frame_->Push(eax); //
// Introduce shadow labels for all escapes from the try block,
// including returns. We should probably try to unify the escaping
// labels and the return label.
// Shadow the labels for all escapes from the try block, including
// returns. During shadowing, the original label is hidden as the
// LabelShadow and operations on the original actually affect the
// shadowing label.
//
// We should probably try to unify the escaping labels and the return
// label.
int nof_escapes = node->escaping_labels()->length();
List<LabelShadow*> shadows(1 + nof_escapes);
shadows.Add(new LabelShadow(&function_return_));
......@@ -2017,6 +2021,8 @@ void CodeGenerator::VisitTryCatch(TryCatch* node) {
is_inside_try_ = was_inside_try;
// Stop the introduced shadowing and count the number of required unlinks.
// After shadowing stops, the original labels are unshadowed and the
// LabelShadows represent the formerly shadowing labels.
int nof_unlinks = 0;
for (int i = 0; i <= nof_escapes; i++) {
shadows[i]->StopShadowing();
......@@ -2042,7 +2048,8 @@ void CodeGenerator::VisitTryCatch(TryCatch* node) {
// next_sp popped.
if (nof_unlinks > 0) __ jmp(&exit);
// Generate unlink code for all used shadow labels.
// Generate unlink code for the (formerly) shadowing labels that have been
// jumped to.
for (int i = 0; i <= nof_escapes; i++) {
if (shadows[i]->is_linked()) {
// Unlink from try chain; be careful not to destroy the TOS.
......@@ -2058,7 +2065,7 @@ void CodeGenerator::VisitTryCatch(TryCatch* node) {
frame_->Pop(Operand::StaticVariable(handler_address));
frame_->Drop(StackHandlerConstants::kSize / kPointerSize - 1);
// next_sp popped.
__ jmp(shadows[i]->shadowed());
__ jmp(shadows[i]->original_label());
}
}
......@@ -2091,9 +2098,13 @@ void CodeGenerator::VisitTryFinally(TryFinally* node) {
// TODO(1222589): remove the reliance of PushTryHandler on a cached TOS
frame_->Push(eax);
// Introduce shadow labels for all escapes from the try block,
// including returns. We should probably try to unify the escaping
// labels and the return label.
// Shadow the labels for all escapes from the try block, including
// returns. During shadowing, the original label is hidden as the
// LabelShadow and operations on the original actually affect the
// shadowing label.
//
// We should probably try to unify the escaping labels and the return
// label.
int nof_escapes = node->escaping_labels()->length();
List<LabelShadow*> shadows(1 + nof_escapes);
shadows.Add(new LabelShadow(&function_return_));
......@@ -2107,8 +2118,9 @@ void CodeGenerator::VisitTryFinally(TryFinally* node) {
VisitStatements(node->try_block()->statements());
is_inside_try_ = was_inside_try;
// Stop the introduced shadowing and count the number of required
// unlinks.
// Stop the introduced shadowing and count the number of required unlinks.
// After shadowing stops, the original labels are unshadowed and the
// LabelShadows represent the formerly shadowing labels.
int nof_unlinks = 0;
for (int i = 0; i <= nof_escapes; i++) {
shadows[i]->StopShadowing();
......@@ -2120,15 +2132,17 @@ void CodeGenerator::VisitTryFinally(TryFinally* node) {
__ Set(ecx, Immediate(Smi::FromInt(FALLING)));
if (nof_unlinks > 0) __ jmp(&unlink);
// Generate code that sets the state for all used shadow labels.
// Generate code to set the state for the (formerly) shadowing labels that
// have been jumped to.
for (int i = 0; i <= nof_escapes; i++) {
if (shadows[i]->is_linked()) {
__ bind(shadows[i]);
if (shadows[i]->shadowed() == &function_return_) {
// Materialize the return value on the stack.
if (shadows[i]->original_label() == &function_return_) {
// If this label shadowed the function return, materialize the
// return value on the stack.
frame_->Push(eax);
} else {
// Fake TOS for break and continue.
// Fake TOS for labels that shadowed breaks and continues.
frame_->Push(Immediate(Factory::undefined_value()));
}
__ Set(ecx, Immediate(Smi::FromInt(JUMPING + i)));
......@@ -2175,12 +2189,12 @@ void CodeGenerator::VisitTryFinally(TryFinally* node) {
frame_->Pop(eax);
break_stack_height_ -= kFinallyStackSize;
// Generate code that jumps to the right destination for all used
// shadow labels.
// Generate code to jump to the right destination for all used (formerly)
// shadowing labels.
for (int i = 0; i <= nof_escapes; i++) {
if (shadows[i]->is_bound()) {
__ cmp(Operand(ecx), Immediate(Smi::FromInt(JUMPING + i)));
__ j(equal, shadows[i]->shadowed());
__ j(equal, shadows[i]->original_label());
}
}
......
Markdown is supported
0% or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment