diff options
| author | Erik Verbruggen <erik.verbruggen@digia.com> | 2014-05-14 14:44:27 +0200 |
|---|---|---|
| committer | Erik Verbruggen <erik.verbruggen@digia.com> | 2014-06-13 10:29:33 +0200 |
| commit | d74927cf5d6b6601e9ac01c22475c2cbe07f1a0e (patch) | |
| tree | 1e67e34da64e87adf1f615d9b9bafa8bec38ece4 /src/qml/compiler/qv4isel_moth.cpp | |
| parent | cb0a47a48d5dc0ce4f5e8cfa68a39cd4cbfde11c (diff) | |
V4 RegAlloc: change life-time intervals from closed to half-open.
There are two changes in this patch, that go hand-in-hand. First, when
re-numbering the statements in order of occurrence in the scheduled
basic-blocks, the (new) position is not stored in the statement itself,
but in the LifeTimeIntervals class. This makes it possible to re-use
information gathered during SSA formation or optimization.
The re-numbering itself has also changed, resulting in some minor
changes to the life-time interval calculation. The new numbering
is described in LifeTimeIntervals::renumber(). The reason is to make it
easy for the register allocator and stack-slot allocator to distinguish
between definition of a temporary and its uses. Example:
20: %3 = %2 + %1
22: print(%3)
If the life-time of %2 or %1 ends at 20, then at the point that %3 gets
assigned, it can re-use the storage occupied by %1 or %2. Also, when
both %1 and %2 need to get a register assigned (because they were
spilled to the stack, for example), %3 should be allocated "after" both
%1 and %2. So, instead of having a closed interval of [20-22] for %3, we
want to use an open interval of (20-22]. To simulate the "open" part, the
life-time of %3 is set to [21-22]. So, all statements live on even
positions, and temporaries defined by a statement start at
statmentPosition + 1.
Change-Id: I0eda2c653b0edf1a529bd0762d338b0ea9a66aa0
Sanity-Review: Qt Sanity Bot <qt_sanitybot@qt-project.org>
Reviewed-by: Lars Knoll <lars.knoll@digia.com>
Diffstat (limited to 'src/qml/compiler/qv4isel_moth.cpp')
| -rw-r--r-- | src/qml/compiler/qv4isel_moth.cpp | 13 |
1 files changed, 8 insertions, 5 deletions
diff --git a/src/qml/compiler/qv4isel_moth.cpp b/src/qml/compiler/qv4isel_moth.cpp index 18877565da..c684aa3e79 100644 --- a/src/qml/compiler/qv4isel_moth.cpp +++ b/src/qml/compiler/qv4isel_moth.cpp @@ -174,7 +174,12 @@ class AllocateStackSlots: protected ConvertTemps QBitArray _slotIsInUse; IR::Function *_function; - int position(IR::Stmt *s) const + int defPosition(IR::Stmt *s) const + { + return usePosition(s) + 1; + } + + int usePosition(IR::Stmt *s) const { return _intervals->positionForStatement(s); } @@ -222,8 +227,6 @@ protected: virtual void process(IR::Stmt *s) { - Q_ASSERT(position(s) > 0); - // qDebug("L%d statement %d:", _currentBasicBlock->index, s->id); if (IR::Phi *phi = s->asPhi()) { @@ -232,7 +235,7 @@ protected: // purge ranges no longer alive: for (int i = 0; i < _live.size(); ) { const IR::LifeTimeInterval *lti = _live.at(i); - if (lti->end() < position(s)) { + if (lti->end() < usePosition(s)) { // qDebug() << "\t - moving temp" << lti->temp().index << "to handled, freeing slot" << _stackSlotForTemp[lti->temp().index]; _live.remove(i); Q_ASSERT(_slotIsInUse[_stackSlotForTemp[lti->temp().index]]); @@ -246,7 +249,7 @@ protected: // active new ranges: while (!_unhandled.isEmpty()) { IR::LifeTimeInterval *lti = _unhandled.last(); - if (lti->start() > position(s)) + if (lti->start() > defPosition(s)) break; // we're done Q_ASSERT(!_stackSlotForTemp.contains(lti->temp().index)); _stackSlotForTemp[lti->temp().index] = allocateFreeSlot(); |