tree ba23edb740cffddca57c66323abe88d1d1779adb
parent 9b0e9218d89ca3dc56584cedb8600db75c767d1b
author Ben Clayton <bclayton@google.com> 1687279341 +0000
committer Dawn LUCI CQ <dawn-scoped@luci-project-accounts.iam.gserviceaccount.com> 1687279341 +0000

[tint][ir] Make ControlInstructions regular instructions

Instead of branches.

This change removes ControlInstruction merge blocks from the IR.

These instructions instead act as regular instructions, that have other
instructions that follow them. Instead of using merge-block parameters,
the ControlInstructions can emit multiple result values, which are
passed down from the corresponding exit instructions.

This:
* Significantly reduces the verbosity of the IR.
* Removes the need to walk down merge-blocks to find all the
  instructions of a given scope. This in turn removes the chance of
  using recursion to walk instruction lists, which is likely to cause
  stack-overflows.
* Simplifies validation, in that later instructions cannot use values
  declared inside ControlInstruction blocks.
* Overall reduces complexity (I believe - YMMV).

Change-Id: I2f7d9e0f97113c8076dafc6541980e87bc21a62a
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/134960
Reviewed-by: James Price <jrprice@google.com>
Kokoro: Kokoro <noreply+kokoro@google.com>
Commit-Queue: Ben Clayton <bclayton@google.com>
Reviewed-by: Dan Sinclair <dsinclair@chromium.org>