powerpc needs -O2 -fno-optimize-sibling-calls for qstring.cpp, not just -O2.
Not needed long-term as the relevant g++ bug is fixed in GCC 4.4.

--- a/mkspecs/linux-g++/qmake.conf
+++ b/mkspecs/linux-g++/qmake.conf
@@ -11,3 +11,8 @@ QMAKE_INCREMENTAL_STYLE = sublib
 include(../common/g++.conf)
 include(../common/linux.conf)
 load(qt_config)
+
+equals(QT_ARCH, powerpc) {
+    QMAKE_CFLAGS_RELEASE   += -fno-optimize-sibling-calls
+    QMAKE_CXXFLAGS_RELEASE += -fno-optimize-sibling-calls
+}