Fix map insertion that is elided in release build.

The assert() macro doesn't actually execute its body in Release builds, so using
it to check cache invariants requires that the insertion be outside of the
assert() statement. This change does that, and also makes sure to return the
actual map contents.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@284898 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed