[polly] Skip instructions of different function in isHoistableLoad. (#118963)

After patch 5ce47a5, some assert crashes occur in Polly. This issue
arises because an instruction from one function queries the Dominator
Tree (DT) of another function. To fix this, the `isHoistableLoad`
function now skips instructions that belong to different function while
iterating.

polly/lib/Support/ScopHelper.cpp

@@ -604,7 +604,8 @@ bool polly::isHoistableLoad(LoadInst *LInst, Region &R, LoopInfo &LI,
 
   for (auto *User : Ptr->users()) {
     auto *UserI = dyn_cast<Instruction>(User);
-    if (!UserI || !R.contains(UserI))
+    if (!UserI || UserI->getFunction() != LInst->getFunction() ||
+        !R.contains(UserI))
       continue;
     if (!UserI->mayWriteToMemory())
       continue;

polly/test/ScopDetect/dom-tree-crash.ll

@@ -0,0 +1,31 @@
+; RUN: opt %loadNPMPolly '-passes=print<polly-detect>' -disable-output < %s 2>&1 | FileCheck %s
+
+; CHECK: Detected Scops in Function foo
+
+; This unit test case is to check if the following IR does not crash in isHoistableLoad function during Scop Detection.
+
+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128-Fn32"
+target triple = "aarch64-unknown-linux-gnueabi"
+
+define void @foo(ptr %block) {
+entry:
+  br label %for.body
+
+for.cond1.preheader:                              ; preds = %for.body
+  %0 = load ptr, ptr null, align 8
+  %1 = load i16, ptr %block, align 2
+  %2 = load i16, ptr %0, align 2
+  br label %foo.exit
+
+for.body:                                         ; preds = %for.body, %entry
+  br i1 false, label %for.cond1.preheader, label %for.body
+
+foo.exit:                                     ; preds = %for.cond1.preheader
+  ret void
+}
+
+define void @init_foo() {
+entry:
+  store ptr null, ptr null, align 8
+  ret void
+}