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

[Matt Arsenault via llvm-commits]

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+# 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
+
+## Also verify that the store to the stack slot still exists.
+
+# CHECK-LABEL: bb.5:
+# CHECK: MOV64mi32 $rbp, 1, $noreg, -48, $noreg, 0 :: (store (s64) into %stack.0)
+# CHECK-LABEL: bb.6:
+
+
+--- |
+  define void @_ZN1g1jEv(ptr %this, i1 %cmp36, ptr %ref.tmp5) {
+  entry:
+    ret void
+  }
+
+...
+---
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arsenm wrote:

Simplify this down to one block? 

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