[llvm] [AArch64] New pass for code layout optimizations. (PR #184434)

[Florian Hahn via llvm-commits]

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@@ -0,0 +1,262 @@
+//===-- AArch64CodeLayoutOpt.cpp - Code Layout Optimizations --===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+//
+// This pass runs after instruction scheduling and employs code layout
+// optimizations for certain patterns.
+//
+// Option -aarch64-code-layout-opt-enable selects instruction pairs to optimize:
+//   cmp-csel:   Enable CMP/CMN-CSEL code layout optimization
+//   fcmp-fcsel: Enable FCMP-FCSEL code layout optimization
+//
+// The initial implementation induces function alignment when a supported
+// pattern is detected, and possibly instruction-alignment when a pair would
+// straddle cache-lines.
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fhahn wrote:

I think this needs updating, AFAICT the code here now always aligns before the first instruction of the pair?

https://github.com/llvm/llvm-project/pull/184434