[llvm] [CodeGen] Correctly handle non-standard cases in RemoveLoadsIntoFakeUses (PR #111551)

[Matt Arsenault via llvm-commits]

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@@ -0,0 +1,74 @@
+# Ensure that loads into FAKE_USEs are correctly removed by the
+# remove-loads-into-fake-uses pass.
+# RUN: llc -run-pass remove-loads-into-fake-uses -mtriple=x86_64-unknown-linux -debug-only=remove-loads-into-fake-uses 2>&1 -o - %s | FileCheck %s --implicit-check-not=DELETING
+# REQUIRES: asserts
+#
+## We ensure that the load into the FAKE_USE is removed, along with the FAKE_USE
+## itself, even when the FAKE_USE is for a subregister of the move, and that we
+## correctly handle situations where FAKE_USE has additional `killed` operands
+## added by other passes.
+
+# CHECK: DELETING: renamable $rax = MOV64rm $rbp
+# CHECK: DELETING: FAKE_USE renamable $eax
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arsenm wrote:

Positively checking the debug output is fine, but much less preferably to concrete result checks. Negative checks of debug output is dangerous since it silently stops working if the printing ever changes 

https://github.com/llvm/llvm-project/pull/111551