[NewGVN] Surround with parens to clarify allegedly ambiguous precedence.

This Placates GCC7 with -Werror. Also, clang-format the assertions
while I'm here.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@299895 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed