[IndVars] Add test for #68260 (NFC)

Author: nikic

llvm/test/Transforms/IndVarSimplify/pr68260.ll

@@ -0,0 +1,53 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 3
+; RUN: opt -S -passes='print<scalar-evolution>,loop(loop-unroll-full,indvars)' < %s 2>/dev/null | FileCheck %s
+@g = constant [5 x i32] [i32 0, i32 1, i32 2, i32 3, i32 4]
+
+declare void @use(i32)
+
+; FIXME: This is a miscompile.
+define void @test() {
+; CHECK-LABEL: define void @test() {
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    br label [[LOOP:%.*]]
+; CHECK:       loop:
+; CHECK-NEXT:    br label [[LOOP2:%.*]]
+; CHECK:       loop2:
+; CHECK-NEXT:    br i1 false, label [[LOOP2]], label [[LOOP_LATCH:%.*]], !llvm.loop [[LOOP0:![0-9]+]]
+; CHECK:       loop.latch:
+; CHECK-NEXT:    call void @use(i32 4)
+; CHECK-NEXT:    br label [[LOOP2_1:%.*]]
+; CHECK:       loop2.1:
+; CHECK-NEXT:    br i1 false, label [[LOOP2_1]], label [[LOOP_LATCH_1:%.*]], !llvm.loop [[LOOP0]]
+; CHECK:       loop.latch.1:
+; CHECK-NEXT:    call void @use(i32 4)
+; CHECK-NEXT:    ret void
+;
+entry:
+  br label %loop
+
+loop:
+  %iv = phi i64 [ 0, %entry ], [ %iv.next, %loop.latch ]
+  %iv.next = add i64 %iv, 1
+  br label %loop2
+
+loop2:
+  %iv2 = phi i64 [ 0, %loop ], [ %iv2.next, %loop2 ]
+  %iv2.next = add i64 %iv2, 1
+  %idx = add i64 %iv, %iv2
+  %gep = getelementptr i32, ptr @g, i64 %idx
+  %load = load i32, ptr %gep
+  %cmp2 = icmp ne i64 %iv2, 3
+  br i1 %cmp2, label %loop2, label %loop.latch, !llvm.loop !0
+
+loop.latch:
+  %load.lcssa = phi i32 [ %load, %loop2 ]
+  call void @use(i32 %load)
+  %cmp = icmp ne i64 %iv, 1
+  br i1 %cmp, label %loop, label %exit
+
+exit:
+  ret void
+}
+
+!0 = distinct !{!0, !1}
+!1 = !{!"llvm.loop.unroll.disable", i1 true}