[GlobalISel] fix a compilation error with gcc 6.3.0
With gcc 6.3.0, I hit the following compilation error:
../lib/CodeGen/GlobalISel/Combiner.cpp: In member function
‘bool llvm::Combiner::combineMachineInstrs(llvm::MachineFunction&,
llvm::GISelCSEInfo*)’:
../lib/CodeGen/GlobalISel/Combiner.cpp:156:54: error: suggest parentheses
around ‘&&’ within ‘||’ [-Werror=parentheses]
assert(!CSEInfo || !errorToBool(CSEInfo->verify()) &&
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~
"CSEInfo is not consistent. Likely missing calls to "
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
"observer on mutations");
Fix the code as suggested by the compiler.