[llvm] GlobalISel lane masks merging (PR #73337)

[Pierre van Houtryve via llvm-commits]

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@@ -0,0 +1,213 @@
+//===-- AMDGPUGlobalISelDivergenceLowering.cpp ----------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+// GlobalISel pass that selects divergent i1 phis as lane mask phis.
+// Lane mask merging uses same algorithm as SDAG in SILowerI1Copies.
+// Handles all cases of temporal divergence.
+//
+// For divergent non-phi i1 and uniform i1 uses outside of the cycle this pass
+// currently depends on LCSSA to insert phis with one incoming.
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Pierre-vh wrote:

really small nit: Use three slashes + start with `\file`, first line should be `/// \file`

https://github.com/llvm/llvm-project/pull/73337