diff --git a/llvm/lib/Transforms/Scalar/LoopFlatten.cpp b/llvm/lib/Transforms/Scalar/LoopFlatten.cpp
--- a/llvm/lib/Transforms/Scalar/LoopFlatten.cpp
+++ b/llvm/lib/Transforms/Scalar/LoopFlatten.cpp
@@ -762,6 +762,7 @@
   // deleted, and any information that have about the outer loop invalidated.
   SE->forgetLoop(FI.OuterLoop);
   SE->forgetLoop(FI.InnerLoop);
+  SE->forgetBlockAndLoopDispositions();
   if (U)
     U->markLoopAsDeleted(*FI.InnerLoop, FI.InnerLoop->getName());
   LI->erase(FI.InnerLoop);
diff --git a/llvm/test/Transforms/LoopFlatten/pr58865.ll b/llvm/test/Transforms/LoopFlatten/pr58865.ll
new file mode 100644
--- /dev/null
+++ b/llvm/test/Transforms/LoopFlatten/pr58865.ll
@@ -0,0 +1,51 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt -loop-flatten -verify-scev -S < %s | FileCheck %s
+;
+define void @sum_2d(ptr %p) {
+; CHECK-LABEL: @sum_2d(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[FLATTEN_TRIPCOUNT:%.*]] = mul i16 1, 1
+; CHECK-NEXT:    br label [[OUTER:%.*]]
+; CHECK:       outer:
+; CHECK-NEXT:    [[SUM_04:%.*]] = phi i16 [ 0, [[ENTRY:%.*]] ], [ [[DOTLCSSA:%.*]], [[OUTER_LATCH:%.*]] ]
+; CHECK-NEXT:    [[OUTER_IV:%.*]] = phi i16 [ 0, [[ENTRY]] ], [ [[OUTER_IV_NEXT:%.*]], [[OUTER_LATCH]] ]
+; CHECK-NEXT:    br label [[INNER:%.*]]
+; CHECK:       inner:
+; CHECK-NEXT:    [[SUM_12:%.*]] = phi i16 [ [[SUM_04]], [[OUTER]] ]
+; CHECK-NEXT:    [[INNER_IV:%.*]] = phi i16 [ 0, [[OUTER]] ]
+; CHECK-NEXT:    [[TMP0:%.*]] = load i16, ptr [[P:%.*]], align 1
+; CHECK-NEXT:    [[INNER_IV_NEXT:%.*]] = add nsw i16 [[INNER_IV]], 1
+; CHECK-NEXT:    [[CMP2:%.*]] = icmp slt i16 [[INNER_IV]], 0
+; CHECK-NEXT:    br label [[OUTER_LATCH]]
+; CHECK:       outer.latch:
+; CHECK-NEXT:    [[DOTLCSSA]] = phi i16 [ [[TMP0]], [[INNER]] ]
+; CHECK-NEXT:    [[OUTER_IV_NEXT]] = add nsw i16 [[OUTER_IV]], 1
+; CHECK-NEXT:    [[CMP:%.*]] = icmp slt i16 [[OUTER_IV_NEXT]], [[FLATTEN_TRIPCOUNT]]
+; CHECK-NEXT:    br i1 [[CMP]], label [[OUTER]], label [[EXIT:%.*]]
+; CHECK:       exit:
+; CHECK-NEXT:    ret void
+;
+entry:
+  br label %outer
+
+outer:                                         ; preds = %outer.latch, %entry
+  %sum.04 = phi i16 [ 0, %entry ], [ %0, %outer.latch ]
+  %outer.iv = phi i16 [ 0, %entry ], [ %outer.iv.next, %outer.latch ]
+  br label %inner
+
+inner:                                        ; preds = %inner, %outer
+  %sum.12 = phi i16 [ %sum.04, %outer ], [ %0, %inner ]
+  %inner.iv = phi i16 [ 0, %outer ], [ %inner.iv.next, %inner ]
+  %0 = load i16, ptr %p, align 1
+  %inner.iv.next = add nsw i16 %inner.iv, 1
+  %cmp2 = icmp slt i16 %inner.iv, 0
+  br i1 %cmp2, label %inner, label %outer.latch
+
+outer.latch:                                         ; preds = %inner
+  %outer.iv.next = add nsw i16 %outer.iv, 1
+  %cmp = icmp slt i16 %outer.iv.next, 0
+  br i1 %cmp, label %outer, label %exit
+
+exit:                                         ; preds = %outer.latch
+  ret void
+}