[all-commits] [llvm/llvm-project] 4abdb8: [SSAUpdater] Avoid un-necessary SmallVector stores...

[Jeremy Morse via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 4abdb85ef2b659a0ee919a4509dd6a82901351b5
      https://github.com/llvm/llvm-project/commit/4abdb85ef2b659a0ee919a4509dd6a82901351b5
  Author: Jeremy Morse <jeremy.morse at sony.com>
  Date:   2024-07-16 (Tue, 16 Jul 2024)

  Changed paths:
    M llvm/include/llvm/Support/GenericIteratedDominanceFrontier.h

  Log Message:
  -----------
  [SSAUpdater] Avoid un-necessary SmallVector stores (#97820)

The default template for the generic IDF calculator fetching
block-children will, by default:
 * Fetch the children range from the relevant `GraphTraits`,
 * Store all child nodes in a `SmallVector`,
 * Return that `SmallVector` into the IDF calculator.

The only place this `SmallVector` is used is in a for-range loop... thus
there's no reason why we can't just iterate over the child range from
`GraphTraits`, instead of storing all the nodes locally then iterating
over the local copy. (If the children of a node change during IDF
calculation, everything is broken anyway).

This yields a 0.14% debug-info build performance improvement on the
compile time tracker, as InstrRefBasedLDV uses the SSA updater
intensively on all functions.



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