Please review the following change that switches to clang-style warning disabling on AIX, and adjusts the warning disabling to current needs .
Recently the jdk/jdk build on AIX switched to xlc16/xlclang. This means we can now use the standard clang-style warning disabling (the old legacy qsuppress warning disablings from legacy xlc might not fully work any more). I think we are pretty close in reducing the compiler warnings to 0 on AIX, which would make it possible to build with warnings as errors at some point in the future . In a first step I would disable these warnings in HS for xlc16/xlclang : tautological-compare : (seen in os_aix.cpp) /jdk/src/hotspot/os/aix/os_aix.cpp:2400:15: warning: comparison of unsigned expression >= 0 is always true [-Wtautological-compare] if (bytes >= Use64KPagesThreshold) { ~~~~~ ^ ~~~~~~~~~~~~~~~~~~~~ /jdk/src/hotspot/os/aix/os_aix.cpp:2607:15: warning: comparison of unsigned expression >= 0 is always true [-Wtautological-compare] if (bytes >= Use64KPagesThreshold) { In the product build the "Use64KPagesThreshold" is a constant so clang complains . However in the (fast)debug builds one can set Use64KPagesThreshold with an -XX setting. So I think it is best to disable the warning. shift-negative-value : (seen in c1_LIRGenerator_ppc.cpp) /jdk/src/hotspot/cpu/ppc/c1_LIRGenerator_ppc.cpp:429:97: warning: shifting a negative signed value is undefined [-Wshift-negative-value] (x->op() == Bytecodes::_lsub && right.value()->type()->as_LongConstant()->value() == ((-1)<<15)) ) { ~~~~^ /jdk/src/hotspot/cpu/ppc/c1_LIRGenerator_ppc.cpp:483:96: warning: shifting a negative signed value is undefined [-Wshift-negative-value] (x->op() == Bytecodes::_isub && right.value()->type()->as_IntConstant()->value() == ((-1)<<15)) ) { We could probably replace the -1 shift by a constant but I think it is nicely readable . Bug/webrev : https://bugs.openjdk.java.net/browse/JDK-8228426 http://cr.openjdk.java.net/~mbaesken/webrevs/8228426.0/ Thanks, Matthias