Implement new transform UnwindDiscardFunctions that replaces discard
statements with setting a module-level bool, adds a check and return for
this bool after every function call that may discard, and finally
invokes a single function that executes a discard from top-level
functions.
Regenerated tests and remove HLSL ones that used to fail FXC because it
had difficulty with discard.
Bug: tint:1478
Bug: chromium:1118
Change-Id: I09d680f59e2d5d0cad907bfbbdd426aae76d4bf3
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/84221
Reviewed-by: James Price <jrprice@google.com>
Reviewed-by: Ben Clayton <bclayton@google.com>
Kokoro: Kokoro <noreply+kokoro@google.com>
Commit-Queue: Antonio Maiorano <amaiorano@google.com>
66d6668372