V4: fix range sorting

When a life-time interval is split from another interval, it has to come
before an interval that starts at the same position but is not split.

This also means that a means that the all ranges in a split interval
are uses, which is important for allocation: all incoming parameters for
an operation need to be allocated before allocating a register for the
result as the result will only start its life "at the end" of the
operation.

This patch fixes a problem register allocation is done in a function
where register pressure is high (e.g. on platforms that have few
registers to start with). Specifically, crypto.js on x86 triggered it.

Change-Id: Iee3e5d82a887b8de573dfc23513844143d0c8073
Reviewed-by: Albert Astals Cid <albert.astals@canonical.com>
Reviewed-by: Simon Hausmann <simon.hausmann@digia.com>
Reviewed-by: Fawzi Mohamed <fawzi.mohamed@digia.com>
Reviewed-by: Lars Knoll <lars.knoll@digia.com>

1 files changed, 6 insertions, 3 deletions

diff --git a/src/qml/compiler/qv4ssa.cpp b/src/qml/compiler/qv4ssa.cpp
index 44c93df4c9..594c38d109 100644
--- a/src/qml/compiler/qv4ssa.cpp
+++ b/src/qml/compiler/qv4ssa.cpp
@@ -3705,9 +3705,12 @@ void LifeTimeInterval::dump(QTextStream &out) const {
 }
 
 bool LifeTimeInterval::lessThan(const LifeTimeInterval &r1, const LifeTimeInterval &r2) {
-    if (r1._ranges.first().start == r2._ranges.first().start)
-        return r1._ranges.last().end < r2._ranges.last().end;
-    else
+    if (r1._ranges.first().start == r2._ranges.first().start) {
+        if (r1.isSplitFromInterval() == r2.isSplitFromInterval())
+            return r1._ranges.last().end < r2._ranges.last().end;
+        else
+            return r1.isSplitFromInterval();
+    } else
         return r1._ranges.first().start < r2._ranges.first().start;
 }