This patch fixes PR40795, where constant-valued variable locations can
"leak" into blocks placed at higher addresses. The root of this is that
DbgEntityHistoryCalculator terminates all register variable locations at
the end of each block, but not constant-value variable locations.
Fixing this requires constant-valued DBG_VALUE instructions to be
broadcast into all blocks where the variable location remains valid, as
documented in the LiveDebugValues section of SourceLevelDebugging.rst,
and correct termination in DbgEntityHistoryCalculator.
Differential Revision: https://reviews.llvm.org/D59431
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@359426 91177308-0d34-0410-b5e6-96231b3b80d8
74e964e3d1