[all-commits] [llvm/llvm-project] a80181: [DebugInfo][InstrRef][NFC] Free resources at an ea...

[Jeremy Morse via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: a80181a81ea44215e49e5da1457614ec0bd44111
      https://github.com/llvm/llvm-project/commit/a80181a81ea44215e49e5da1457614ec0bd44111
  Author: Jeremy Morse <jeremy.morse at sony.com>
  Date:   2022-02-02 (Wed, 02 Feb 2022)

  Changed paths:
    M llvm/lib/CodeGen/LiveDebugValues/InstrRefBasedImpl.cpp
    M llvm/lib/CodeGen/LiveDebugValues/InstrRefBasedImpl.h

  Log Message:
  -----------
  [DebugInfo][InstrRef][NFC] Free resources at an earlier stage

This patch releases some memory from InstrRefBasedLDV earlier that it would
otherwise. The underlying problem is:
 * We store a big table of "live in values for each block",
 * We translate that into DBG_VALUE instructions in each block,

And both exist in memory at the same time, which needlessly doubles that
information. The most of what this patch does is: as we progressively
translate live-in information into DBG_VALUEs, we free the variable-value /
machine-value tracking information as we go, which significantly reduces
peak memory.

While I'm here, also add a clear method to wipe variable assignments that
have been accumulated into VLocTracker objects, and turn a DenseMap into
a SmallDenseMap to avoid an initial allocation.

Differential Revision: https://reviews.llvm.org/D118453