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Unified Diff: src/arm/jump-target-arm.cc

Issue 165230: Eliminate most of the jump target jumping, branching, and binding... (Closed) Base URL: http://v8.googlecode.com/svn/branches/bleeding_edge/
Patch Set: Created 11 years, 4 months ago
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Index: src/arm/jump-target-arm.cc
===================================================================
--- src/arm/jump-target-arm.cc (revision 2654)
+++ src/arm/jump-target-arm.cc (working copy)
@@ -47,23 +47,29 @@
ASSERT(cgen()->HasValidEntryRegisters());
if (is_bound()) {
- // Backward jump. There is an expected frame to merge to.
+ // Backward jump. There already a frame expectation at the target.
ASSERT(direction_ == BIDIRECTIONAL);
- cgen()->frame()->PrepareMergeTo(entry_frame_);
cgen()->frame()->MergeTo(entry_frame_);
cgen()->DeleteFrame();
- __ jmp(&entry_label_);
} else {
- // Preconfigured entry frame is not used on ARM.
- ASSERT(entry_frame_ == NULL);
- // Forward jump. The current frame is added to the end of the list
- // of frames reaching the target block and a jump to the merge code
- // is emitted.
- AddReachingFrame(cgen()->frame());
- RegisterFile empty;
- cgen()->SetFrame(NULL, &empty);
- __ jmp(&merge_labels_.last());
+ // Use the current frame as the expected one at the target if necessary.
+ if (entry_frame_ == NULL) {
+ entry_frame_ = cgen()->frame();
+ RegisterFile empty;
+ cgen()->SetFrame(NULL, &empty);
+ } else {
+ cgen()->frame()->MergeTo(entry_frame_);
+ cgen()->DeleteFrame();
+ }
+
+ // The predicate is_linked() should now be true. The implementation
Erik Corry 2009/08/10 10:56:45 This comment doesn't explain itself very well.
Kevin Millikin (Chromium) 2009/08/10 11:11:31 Reworded: "The predicate is_linked() should be ma
+ // uses the presence of a frame pointer in the reaching_frames_ list.
+ if (!is_linked()) {
+ reaching_frames_.Add(NULL);
+ ASSERT(is_linked());
+ }
}
+ __ jmp(&entry_label_);
}
@@ -74,56 +80,21 @@
ASSERT(direction_ == BIDIRECTIONAL);
// Backward branch. We have an expected frame to merge to on the
// backward edge.
-
- // Swap the current frame for a copy (we do the swapping to get
- // the off-frame registers off the fall through) to use for the
- // branch.
- VirtualFrame* fall_through_frame = cgen()->frame();
- VirtualFrame* branch_frame = new VirtualFrame(fall_through_frame);
- RegisterFile non_frame_registers;
- cgen()->SetFrame(branch_frame, &non_frame_registers);
-
- // Check if we can avoid merge code.
- cgen()->frame()->PrepareMergeTo(entry_frame_);
- if (cgen()->frame()->Equals(entry_frame_)) {
- // Branch right in to the block.
- cgen()->DeleteFrame();
- __ b(cc, &entry_label_);
- cgen()->SetFrame(fall_through_frame, &non_frame_registers);
- return;
- }
-
- // Check if we can reuse existing merge code.
- for (int i = 0; i < reaching_frames_.length(); i++) {
- if (reaching_frames_[i] != NULL &&
- cgen()->frame()->Equals(reaching_frames_[i])) {
- // Branch to the merge code.
- cgen()->DeleteFrame();
- __ b(cc, &merge_labels_[i]);
- cgen()->SetFrame(fall_through_frame, &non_frame_registers);
- return;
- }
- }
-
- // To emit the merge code here, we negate the condition and branch
- // around the merge code on the fall through path.
- Label original_fall_through;
- __ b(NegateCondition(cc), &original_fall_through);
cgen()->frame()->MergeTo(entry_frame_);
- cgen()->DeleteFrame();
- __ b(&entry_label_);
- cgen()->SetFrame(fall_through_frame, &non_frame_registers);
- __ bind(&original_fall_through);
-
} else {
- // Preconfigured entry frame is not used on ARM.
- ASSERT(entry_frame_ == NULL);
- // Forward branch. A copy of the current frame is added to the end
- // of the list of frames reaching the target block and a branch to
- // the merge code is emitted.
- AddReachingFrame(new VirtualFrame(cgen()->frame()));
- __ b(cc, &merge_labels_.last());
+ // Clone the current frame to use as the expected one at the target if
+ // necessary.
+ if (entry_frame_ == NULL) {
+ entry_frame_ = new VirtualFrame(cgen()->frame());
+ }
+ // The predicate is_linked() should now be true. The implementation
+ // uses the presence of a frame pointer in the reaching_frames_ list.
+ if (!is_linked()) {
+ reaching_frames_.Add(NULL);
+ ASSERT(is_linked());
+ }
}
+ __ b(cc, &entry_label_);
}
@@ -139,13 +110,19 @@
ASSERT(cgen()->HasValidEntryRegisters());
ASSERT(!is_linked());
- cgen()->frame()->SpillAll();
+ // Calls are always 'forward' so we use a copy of the current frame (plus
+ // one for a return address) as the expected frame.
+ ASSERT(entry_frame_ == NULL);
VirtualFrame* target_frame = new VirtualFrame(cgen()->frame());
target_frame->Adjust(1);
- // We do not expect a call with a preconfigured entry frame.
- ASSERT(entry_frame_ == NULL);
- AddReachingFrame(target_frame);
- __ bl(&merge_labels_.last());
+ entry_frame_ = target_frame;
+
+ // is_linked() should now be true. The JumpTarget class uses the presence
+ // of a frame pointer in the reaching_frames_ list.
+ reaching_frames_.Add(NULL);
+ ASSERT(is_linked());
+
+ __ bl(&entry_label_);
}
@@ -156,168 +133,103 @@
// block.
ASSERT(!cgen()->has_valid_frame() || cgen()->HasValidEntryRegisters());
- if (direction_ == FORWARD_ONLY) {
- // A simple case: no forward jumps and no possible backward jumps.
- if (!is_linked()) {
- // The stack pointer can be floating above the top of the
- // virtual frame before the bind. Afterward, it should not.
- ASSERT(cgen()->has_valid_frame());
- VirtualFrame* frame = cgen()->frame();
- int difference = frame->stack_pointer_ - (frame->element_count() - 1);
- if (difference > 0) {
- frame->stack_pointer_ -= difference;
- __ add(sp, sp, Operand(difference * kPointerSize));
- }
- __ bind(&entry_label_);
- return;
- }
-
- // Another simple case: no fall through, a single forward jump,
- // and no possible backward jumps.
- if (!cgen()->has_valid_frame() && reaching_frames_.length() == 1) {
- // Pick up the only reaching frame, take ownership of it, and
- // use it for the block about to be emitted.
- VirtualFrame* frame = reaching_frames_[0];
- RegisterFile empty;
- cgen()->SetFrame(frame, &empty);
- reaching_frames_[0] = NULL;
- __ bind(&merge_labels_[0]);
-
- // The stack pointer can be floating above the top of the
- // virtual frame before the bind. Afterward, it should not.
- int difference = frame->stack_pointer_ - (frame->element_count() - 1);
- if (difference > 0) {
- frame->stack_pointer_ -= difference;
- __ add(sp, sp, Operand(difference * kPointerSize));
- }
- __ bind(&entry_label_);
- return;
- }
- }
-
- // If there is a current frame, record it as the fall-through. It
- // is owned by the reaching frames for now.
- bool had_fall_through = false;
if (cgen()->has_valid_frame()) {
- had_fall_through = true;
- AddReachingFrame(cgen()->frame()); // Return value ignored.
+ // If there is a current frame we can use it on the fall through.
+ if (entry_frame_ == NULL) {
+ entry_frame_ = new VirtualFrame(cgen()->frame());
+ } else {
+ ASSERT(cgen()->frame()->Equals(entry_frame_));
+ }
+ } else {
+ // If there is no current frame we must have an entry frame which we can
+ // copy.
+ ASSERT(entry_frame_ != NULL);
RegisterFile empty;
- cgen()->SetFrame(NULL, &empty);
+ cgen()->SetFrame(new VirtualFrame(entry_frame_), &empty);
}
- // Compute the frame to use for entry to the block.
- if (entry_frame_ == NULL) {
- ComputeEntryFrame();
+ // is_linked() should now be false. We may have inserted a bogus reaching
+ // frame to make it true, remove it now.
+ if (is_linked()) {
+ reaching_frames_.Clear();
}
- // Some moves required to merge to an expected frame require purely
- // frame state changes, and do not require any code generation.
- // Perform those first to increase the possibility of finding equal
- // frames below.
- for (int i = 0; i < reaching_frames_.length(); i++) {
- if (reaching_frames_[i] != NULL) {
- reaching_frames_[i]->PrepareMergeTo(entry_frame_);
- }
- }
+ __ bind(&entry_label_);
+}
- if (is_linked()) {
- // There were forward jumps. Handle merging the reaching frames
- // and possible fall through to the entry frame.
- // Loop over the (non-null) reaching frames and process any that
- // need merge code. Iterate backwards through the list to handle
- // the fall-through frame first. Set frames that will be
- // processed after 'i' to NULL if we want to avoid processing
- // them.
- for (int i = reaching_frames_.length() - 1; i >= 0; i--) {
- VirtualFrame* frame = reaching_frames_[i];
+void BreakTarget::Jump() {
+ // On ARM we do not currently emit merge code for jumps, so we need to do
+ // it explicitly here. The only merging necessary is to drop extra
+ // statement state from the stack.
+ ASSERT(cgen()->has_valid_frame());
+ int count = cgen()->frame()->height() - expected_height_;
Erik Corry 2009/08/10 10:56:45 Should we assert that count is positive?
Kevin Millikin (Chromium) 2009/08/10 11:11:31 Yea verily. Even better it should go in VirtualFr
+ cgen()->frame()->Drop(count);
+ DoJump();
+}
- if (frame != NULL) {
- // Does the frame (probably) need merge code?
- if (!frame->Equals(entry_frame_)) {
- // We could have a valid frame as the fall through to the
- // binding site or as the fall through from a previous merge
- // code block. Jump around the code we are about to
- // generate.
- if (cgen()->has_valid_frame()) {
- cgen()->DeleteFrame();
- __ b(&entry_label_);
- }
- // Pick up the frame for this block. Assume ownership if
- // there cannot be backward jumps.
- RegisterFile empty;
- if (direction_ == BIDIRECTIONAL) {
- cgen()->SetFrame(new VirtualFrame(frame), &empty);
- } else {
- cgen()->SetFrame(frame, &empty);
- reaching_frames_[i] = NULL;
- }
- __ bind(&merge_labels_[i]);
- // Loop over the remaining (non-null) reaching frames,
- // looking for any that can share merge code with this one.
- for (int j = 0; j < i; j++) {
- VirtualFrame* other = reaching_frames_[j];
- if (other != NULL && other->Equals(cgen()->frame())) {
- // Set the reaching frame element to null to avoid
- // processing it later, and then bind its entry label.
- reaching_frames_[j] = NULL;
- __ bind(&merge_labels_[j]);
- }
- }
+void BreakTarget::Jump(Result* arg) {
+ // On ARM we do not currently emit merge code for jumps, so we need to do
+ // it explicitly here. The only merging necessary is to drop extra
+ // statement state from the stack.
+ ASSERT(cgen()->has_valid_frame());
+ int count = cgen()->frame()->height() - expected_height_;
+ cgen()->frame()->Drop(count);
+ cgen()->frame()->Push(arg);
+ DoJump();
+}
- // Emit the merge code.
- cgen()->frame()->MergeTo(entry_frame_);
- } else if (i == reaching_frames_.length() - 1 && had_fall_through) {
- // If this is the fall through, and it didn't need merge
- // code, we need to pick up the frame so we can jump around
- // subsequent merge blocks if necessary.
- RegisterFile empty;
- cgen()->SetFrame(frame, &empty);
- reaching_frames_[i] = NULL;
- }
- }
- }
- // The code generator may not have a current frame if there was no
- // fall through and none of the reaching frames needed merging.
- // In that case, clone the entry frame as the current frame.
- if (!cgen()->has_valid_frame()) {
- RegisterFile empty;
- cgen()->SetFrame(new VirtualFrame(entry_frame_), &empty);
- }
+void BreakTarget::Bind() {
+#ifdef DEBUG
+ // All the forward-reaching frames should have been adjusted at the
+ // jumps to this target.
+ for (int i = 0; i < reaching_frames_.length(); i++) {
+ ASSERT(reaching_frames_[i] == NULL ||
+ reaching_frames_[i]->height() == expected_height_);
+ }
+#endif
+ // Drop leftover statement state from the frame before merging, even
+ // on the fall through. This is so we can bind the return target
+ // with state on the frame.
+ if (cgen()->has_valid_frame()) {
+ int count = cgen()->frame()->height() - expected_height_;
+ // On ARM we do not currently emit merge code at binding sites, so we need
+ // to do it explicitly here. The only merging necessary is to drop extra
+ // statement state from the stack.
+ cgen()->frame()->Drop(count);
+ }
- // There may be unprocessed reaching frames that did not need
- // merge code. They will have unbound merge labels. Bind their
- // merge labels to be the same as the entry label and deallocate
- // them.
- for (int i = 0; i < reaching_frames_.length(); i++) {
- if (!merge_labels_[i].is_bound()) {
- reaching_frames_[i] = NULL;
- __ bind(&merge_labels_[i]);
- }
- }
+ DoBind();
+}
- // There are non-NULL reaching frames with bound labels for each
- // merge block, but only on backward targets.
- } else {
- // There were no forward jumps. There must be a current frame and
- // this must be a bidirectional target.
- ASSERT(reaching_frames_.length() == 1);
- ASSERT(reaching_frames_[0] != NULL);
- ASSERT(direction_ == BIDIRECTIONAL);
- // Use a copy of the reaching frame so the original can be saved
- // for possible reuse as a backward merge block.
- RegisterFile empty;
- cgen()->SetFrame(new VirtualFrame(reaching_frames_[0]), &empty);
- __ bind(&merge_labels_[0]);
- cgen()->frame()->MergeTo(entry_frame_);
+void BreakTarget::Bind(Result* arg) {
+#ifdef DEBUG
+ // All the forward-reaching frames should have been adjusted at the
+ // jumps to this target.
+ for (int i = 0; i < reaching_frames_.length(); i++) {
+ ASSERT(reaching_frames_[i] == NULL ||
+ reaching_frames_[i]->height() == expected_height_ + 1);
}
-
- __ bind(&entry_label_);
+#endif
+ // Drop leftover statement state from the frame before merging, even
+ // on the fall through. This is so we can bind the return target
+ // with state on the frame.
+ if (cgen()->has_valid_frame()) {
+ int count = cgen()->frame()->height() - expected_height_;
+ // On ARM we do not currently emit merge code at binding sites, so we need
+ // to do it explicitly here. The only merging necessary is to drop extra
+ // statement state from the stack.
+ cgen()->frame()->ForgetElements(count);
+ cgen()->frame()->Push(arg);
+ }
+ DoBind();
+ *arg = cgen()->frame()->Pop();
}
+
#undef __
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