[NFC] Precommit a coroutine test for LoopRotate (#82031)

This is to provide a baseline test for
#81937.

Author: alanzhao1

llvm/test/Transforms/LoopRotate/coroutine.ll

@@ -0,0 +1,45 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 4
+; RUN: opt -S -passes=loop-rotate < %s | FileCheck %s
+
+declare void @bar()
+
+@threadlocalint = thread_local global i32 0, align 4
+
+define void @foo() #0 {
+; CHECK-LABEL: define void @foo(
+; CHECK-SAME: ) #[[ATTR0:[0-9]+]] {
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[TMP0:%.*]] = tail call align 4 ptr @llvm.threadlocal.address.p0(ptr align 4 @threadlocalint)
+; CHECK-NEXT:    [[TMP1:%.*]] = load i32, ptr [[TMP0]], align 4
+; CHECK-NEXT:    [[CMP1:%.*]] = icmp eq i32 [[TMP1]], 0
+; CHECK-NEXT:    br i1 [[CMP1]], label [[COND_END_LR_PH:%.*]], label [[COND_FALSE:%.*]]
+; CHECK:       cond.end.lr.ph:
+; CHECK-NEXT:    br label [[COND_END:%.*]]
+; CHECK:       while.cond.cond.false_crit_edge:
+; CHECK-NEXT:    br label [[COND_FALSE]]
+; CHECK:       cond.false:
+; CHECK-NEXT:    ret void
+; CHECK:       cond.end:
+; CHECK-NEXT:    call void @bar()
+; CHECK-NEXT:    [[TMP2:%.*]] = load i32, ptr [[TMP0]], align 4
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq i32 [[TMP2]], 0
+; CHECK-NEXT:    br i1 [[CMP]], label [[COND_END]], label [[WHILE_COND_COND_FALSE_CRIT_EDGE:%.*]]
+;
+entry:
+  br label %while.cond
+
+while.cond:
+  %1 = tail call align 4 ptr @llvm.threadlocal.address.p0(ptr align 4 @threadlocalint)
+  %2 = load i32, ptr %1, align 4
+  %cmp = icmp eq i32 %2, 0
+  br i1 %cmp, label %cond.end, label %cond.false
+
+cond.false:
+  ret void
+
+cond.end:
+  call void @bar()
+  br label %while.cond
+}
+
+attributes #0 = { presplitcoroutine }