diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -1480,7 +1480,17 @@
                 Pred = CmpInst::getInversePredicate(Pred);
               // Get the knownbits implied by the incoming phi condition.
               auto CR = ConstantRange::makeExactICmpRegion(Pred, *RHSC);
-              Known2 = Known2.unionWith(CR.toKnownBits());
+              KnownBits KnownUnion = Known2.unionWith(CR.toKnownBits());
+              // We can have conflicts here if we are analyzing deadcode (its
+              // impossible for us reach this BB based the icmp).
+              if (KnownUnion.hasConflict()) {
+                // No reason to continue analyzing in a known dead region, so
+                // just resetAll and break. This will cause us to also exit the
+                // outer loop.
+                Known.resetAll();
+                break;
+              }
+              Known2 = KnownUnion;
             }
           }
         }
diff --git a/llvm/test/Analysis/ValueTracking/knownbits-phi-deadcode.ll b/llvm/test/Analysis/ValueTracking/knownbits-phi-deadcode.ll
new file mode 100644
--- /dev/null
+++ b/llvm/test/Analysis/ValueTracking/knownbits-phi-deadcode.ll
@@ -0,0 +1,107 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 2
+; RUN: opt -passes=loop-deletion -S < %s | FileCheck %s
+; This reduced testcase from pr65022. We are only testing that is doesn't crash.
+
+@b = internal unnamed_addr global i1 false
+
+define void @f(i32 %spec.select, ptr nocapture writeonly %c, i1 %tobool.not) local_unnamed_addr {
+; CHECK-LABEL: define void @f
+; CHECK-SAME: (i32 [[SPEC_SELECT:%.*]], ptr nocapture writeonly [[C:%.*]], i1 [[TOBOOL_NOT:%.*]]) local_unnamed_addr {
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[TOBOOL2_NOT:%.*]] = icmp eq i32 [[SPEC_SELECT]], 0
+; CHECK-NEXT:    br label [[L_OUTER:%.*]]
+; CHECK:       L.outer:
+; CHECK-NEXT:    [[I_0_PH:%.*]] = phi i32 [ 1, [[WHILE_COND:%.*]] ], [ 0, [[ENTRY:%.*]] ]
+; CHECK-NEXT:    br label [[L:%.*]]
+; CHECK:       L:
+; CHECK-NEXT:    br i1 [[TOBOOL_NOT]], label [[IF_END:%.*]], label [[IF_THEN:%.*]]
+; CHECK:       if.then:
+; CHECK-NEXT:    store i32 0, ptr [[C]], align 4
+; CHECK-NEXT:    br label [[IF_END]]
+; CHECK:       if.end:
+; CHECK-NEXT:    [[DOTB:%.*]] = load i1, ptr @b, align 1
+; CHECK-NEXT:    [[TMP0:%.*]] = select i1 [[DOTB]], i32 0, i32 1
+; CHECK-NEXT:    [[CMP:%.*]] = icmp sgt i32 [[TMP0]], -1
+; CHECK-NEXT:    br i1 [[CMP]], label [[IF_THEN1:%.*]], label [[WHILE_COND_SPLIT_LOOP_EXIT1:%.*]]
+; CHECK:       if.then1:
+; CHECK-NEXT:    br i1 [[TOBOOL2_NOT]], label [[WHILE_COND_LOOPEXIT:%.*]], label [[IF_THEN3:%.*]]
+; CHECK:       if.then3:
+; CHECK-NEXT:    call void (...) @e()
+; CHECK-NEXT:    br label [[L]]
+; CHECK:       while.cond.split.loop.exit1:
+; CHECK-NEXT:    [[DOTLCSSA:%.*]] = phi i32 [ [[TMP0]], [[IF_END]] ]
+; CHECK-NEXT:    [[NOT_LE:%.*]] = xor i32 [[DOTLCSSA]], 1
+; CHECK-NEXT:    br label [[WHILE_COND]]
+; CHECK:       while.cond.loopexit:
+; CHECK-NEXT:    br label [[WHILE_COND]]
+; CHECK:       while.cond:
+; CHECK-NEXT:    [[H_02:%.*]] = phi i32 [ [[NOT_LE]], [[WHILE_COND_SPLIT_LOOP_EXIT1]] ], [ 0, [[WHILE_COND_LOOPEXIT]] ]
+; CHECK-NEXT:    [[TOBOOL7_NOT:%.*]] = icmp eq i32 [[H_02]], 0
+; CHECK-NEXT:    [[SPEC_SELECT3:%.*]] = select i1 [[TOBOOL7_NOT]], i32 [[I_0_PH]], i32 [[SPEC_SELECT]]
+; CHECK-NEXT:    [[TOBOOL10_NOT:%.*]] = icmp eq i32 [[SPEC_SELECT3]], 0
+; CHECK-NEXT:    br i1 [[TOBOOL10_NOT]], label [[FOR_COND_PREHEADER:%.*]], label [[L_OUTER]]
+; CHECK:       for.cond.preheader:
+; CHECK-NEXT:    [[TOBOOL13_NOT3:%.*]] = icmp eq i32 [[SPEC_SELECT]], 0
+; CHECK-NEXT:    br i1 [[TOBOOL13_NOT3]], label [[FOR_END:%.*]], label [[FOR_COND_FOR_END_CRIT_EDGE:%.*]]
+; CHECK:       for.cond.for.end_crit_edge:
+; CHECK-NEXT:    store i1 true, ptr @b, align 1
+; CHECK-NEXT:    br label [[FOR_END]]
+; CHECK:       for.end:
+; CHECK-NEXT:    ret void
+;
+entry:
+  %tobool2.not = icmp eq i32 %spec.select, 0
+  br label %L.outer
+
+L.outer:  ; preds = %while.cond, %entry
+  %i.0.ph = phi i32 [ 1, %while.cond ], [ 0, %entry ]
+  br label %L
+
+L:  ; preds = %if.then3, %L.outer
+  br i1 %tobool.not, label %if.end, label %if.then
+
+if.then:  ; preds = %L
+  store i32 0, ptr %c, align 4
+  br label %if.end
+
+if.end:  ; preds = %if.then, %L
+  %.b = load i1, ptr @b, align 1
+  %0 = select i1 %.b, i32 0, i32 1
+  %cmp = icmp sgt i32 %0, -1
+  br i1 %cmp, label %if.then1, label %while.cond.split.loop.exit1
+
+if.then1:  ; preds = %if.end
+  br i1 %tobool2.not, label %while.cond.loopexit, label %if.then3
+
+if.then3:  ; preds = %if.then1
+  call void(...) @e()
+  br label %L
+
+while.cond.split.loop.exit1:  ; preds = %if.end
+  %.lcssa = phi i32 [ %0, %if.end ]
+  %not.le = xor i32 %.lcssa, 1
+  br label %while.cond
+
+while.cond.loopexit:  ; preds = %if.then1
+  br label %while.cond
+
+while.cond:  ; preds = %while.cond.loopexit, %while.cond.split.loop.exit1
+  %h.02 = phi i32 [ %not.le, %while.cond.split.loop.exit1 ], [ 0, %while.cond.loopexit ]
+  %tobool7.not = icmp eq i32 %h.02, 0
+  %spec.select3 = select i1 %tobool7.not, i32 %i.0.ph, i32 %spec.select
+  %tobool10.not = icmp eq i32 %spec.select3, 0
+  br i1 %tobool10.not, label %for.cond.preheader, label %L.outer
+
+for.cond.preheader:  ; preds = %while.cond
+  %tobool13.not3 = icmp eq i32 %spec.select, 0
+  br i1 %tobool13.not3, label %for.end, label %for.cond.for.end_crit_edge
+
+for.cond.for.end_crit_edge:  ; preds = %for.cond.preheader
+  store i1 true, ptr @b, align 1
+  br label %for.end
+
+for.end:  ; preds = %for.cond.for.end_crit_edge, %for.cond.preheader
+  ret void
+}
+
+declare void @e(...) local_unnamed_addr