[llvm] [DAG] Add TRUNCATE_SSAT_S/U and TRUNCATE_USAT_U to canCreateUndefOrPoison and computeKnownBits (#152143) (PR #168809)

[Jerry Dang via llvm-commits]

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@@ -0,0 +1,82 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc < %s -mtriple=aarch64 | FileCheck %s
+
+;; ============================================================================
+;; Tests for canCreateUndefOrPoison = false
+;; These verify that freeze operations are correctly eliminated
+;; ============================================================================
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kuroyukiasuna wrote:

Probably don't want freeze elimination at IR level -  would be semantically incorrect, inconsistent with other saturation operations, where poison is propagated.

https://github.com/llvm/llvm-project/pull/168809