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Before emitting code to merge frames, forget the sync flag (telling

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that an element is mirrored in memory) for elements whose target is a
register.  This avoids generating some duplicate merge blocks.

Review URL: http://codereview.chromium.org/40005

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@1403 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
This commit is contained in:
kmillikin@chromium.org 2009-03-03 11:51:59 +00:00
parent 265715d90c
commit 47b20ddf89
1 changed files with 15 additions and 3 deletions
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18
src/virtual-frame.cc
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@ -230,14 +230,19 @@ void VirtualFrame::SpillAll() {
void VirtualFrame::PrepareMergeTo(VirtualFrame* expected) { void VirtualFrame::PrepareMergeTo(VirtualFrame* expected) {
// No code needs to be generated to invalidate valid elements. No // Perform state changes on this frame that will make merge to the
// code needs to be generated to move values to memory if they are // expected frame simpler or else increase the likelihood that his
// already synced. // frame will match another.
for (int i = 0; i < elements_.length(); i++) { for (int i = 0; i < elements_.length(); i++) {
FrameElement source = elements_[i]; FrameElement source = elements_[i];
FrameElement target = expected->elements_[i]; FrameElement target = expected->elements_[i];
if (!target.is_valid() || if (!target.is_valid() ||
(target.is_memory() && !source.is_memory() && source.is_synced())) { (target.is_memory() && !source.is_memory() && source.is_synced())) {
// No code needs to be generated to invalidate valid elements.
// No code needs to be generated to move values to memory if
// they are already synced. We perform those moves here, before
// merging.
if (source.is_register()) { if (source.is_register()) {
// If the frame is the code generator's current frame, we have // If the frame is the code generator's current frame, we have
// to decrement both the frame-internal and global register // to decrement both the frame-internal and global register
@ -249,6 +254,13 @@ void VirtualFrame::PrepareMergeTo(VirtualFrame* expected) {
} }
} }
elements_[i] = target; elements_[i] = target;
} else if (target.is_register() && !target.is_synced() &&
!source.is_memory()) {
// If an element's target is a register that doesn't need to be
// synced, and the element is not in memory, then the sync state
// of the element is irrelevant. We clear the sync bit.
ASSERT(source.is_valid());
elements_[i].clear_sync();
} }
} }
} }