[AArch64] Fix buildbot breakage of ubsan

Fix the ERROR: UndefinedBehaviorSanitizer, reproduced by
  BUILDBOT_REVISION=43ffe2eed llvm-zorg/zorg/buildbot/builders/sanitizers/buildbot_bootstrap_ubsan.sh
It might be also related to llvm#76202

Author: vfdff

llvm/lib/Target/AArch64/AArch64LoadStoreOptimizer.cpp

@@ -2223,7 +2223,9 @@ bool AArch64LoadStoreOpt::isMatchingMovConstInsn(MachineInstr &MemMI,
       return false;
     MBBI = prev_nodbg(MBBI, B);
     MachineInstr &MovzMI = *MBBI;
-    if (MovzMI.getOpcode() == AArch64::MOVZWi) {
+    // Make sure the MOVKWi and MOVZWi set the same register.
+    if (MovzMI.getOpcode() == AArch64::MOVZWi &&
+        MovzMI.getOperand(0).getReg() == MI.getOperand(0).getReg()) {
       unsigned Low = MovzMI.getOperand(1).getImm();
       unsigned High = MI.getOperand(2).getImm() << MI.getOperand(3).getImm();
       Offset = High + Low;

llvm/test/CodeGen/AArch64/large-offset-ldr-merge.mir

@@ -65,3 +65,26 @@ body:             |
     renamable $w8 = MOVKWi $w8, 15, 16, implicit-def $x8
     renamable $w0 = LDRBBroX killed renamable $x0, killed renamable $x8, 0, 0
     RET undef $lr, implicit $w0
+...
+
+# Negative test: MOVZWi and MOVKWi don't set the same register
+---
+name:            LdOffset_different_register_MOVZ_MOVK
+tracksRegLiveness: true
+liveins:
+  - { reg: '$x0', virtual-reg: '' }
+body:             |
+  bb.0.entry:
+    liveins: $x0
+
+    ; CHECK-LABEL: name: LdOffset_different_register_MOVZ_MOVK
+    ; CHECK: liveins: $x0
+    ; CHECK-NEXT: {{  $}}
+    ; CHECK-NEXT: renamable $w7 = MOVZWi 56952, 0
+    ; CHECK-NEXT: renamable $w8 = MOVKWi $w8, 15, 16, implicit-def $x8
+    ; CHECK-NEXT: renamable $w0 = LDRBBroX killed renamable $x0, killed renamable $x8, 0, 0
+    ; CHECK-NEXT: RET undef $lr, implicit $w0
+    renamable $w7 = MOVZWi 56952, 0
+    renamable $w8 = MOVKWi $w8, 15, 16, implicit-def $x8
+    renamable $w0 = LDRBBroX killed renamable $x0, killed renamable $x8, 0, 0
+    RET undef $lr, implicit $w0