[polly] Skip instructions of different function in isHoistableLoad.

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.

Author: kartcq

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
+}