V4 regalloc: fix register spill choice under high pressure.
V4 regalloc: fix register spill choice under high pressure.

When a register is needed for an input parameter of an operation, and
all registers are already in use, do not select a register for spilling
when it is also used in the current operation.

Task-number: QTBUG-38451
Change-Id: I4a8f28cbaadce2dbb9d0c450ccac0ed572936c24
Reviewed-by: Albert Astals Cid <d8d923f3344ab387f1305d27e740c009c5c91ae7@canonical.com>
Reviewed-by: Fawzi Mohamed <7388270c57edd0fabd71d8eb0322d66e3c40e57e@digia.com>
Reviewed-by: Lars Knoll <a812617a4072dcbeb80684eca0f369f0083af109@digia.com>

qmlc/qtdeclarative,mgrunditz/qtdeclarative-2d,qmlc/qtdeclarative,qmlc/qtdeclarative,qmlc/qtdeclarative,mgrunditz/qtdeclarative-2d,qmlc/qtdeclarative,qmlc/qtdeclarative,mgrunditz/qtdeclarative-2d,mgrunditz/qtdeclarative-2d,mgrunditz/qtdeclarative-2d,mgrunditz/qtdeclarative-2d,qmlc/qtdeclarative,qmlc/qtdeclarative,mgrunditz/qtdeclarative-2d