This patch aims to reduce max-rss from instruction referencing, by avoiding
keeping variable value information in memory for too long. Instead of
computing all the variable values then emitting them to DBG_VALUE
instructions, this patch tries to stream the information out through a
depth first search:
* Make use of the fact LexicalScopes gives a depth-number to each lexical
scope,
* Produce a map that identifies the last lexical scope to make use of a
block,
* Enumerate each scope in LexicalScopes' DFS order, solving the variable
value problem,
* After each scope is processed, look for any blocks that won't be used by
any other scope, and emit all the variable information to DBG_VALUE
instructions.
Differential Revision: https://reviews.llvm.org/D118460
9fd9d56dc6