diff --git a/llvm/test/BugPoint/reduce-declarations.ll b/llvm/test/BugPoint/reduce-declarations.ll
new file mode 100644
--- /dev/null
+++ b/llvm/test/BugPoint/reduce-declarations.ll
@@ -0,0 +1,31 @@
+; REQUIRES: plugins
+; RUN: bugpoint -load %llvmshlibdir/BugpointPasses%shlibext %s -output-prefix %t -bugpoint-crashname -silence-passes > /dev/null
+; RUN: llvm-dis %t-reduced-simplified.bc -o - | FileCheck --check-prefix=NONUKE %s
+;
+; RUN: bugpoint -load %llvmshlibdir/BugpointPasses%shlibext %s -output-prefix %t -bugpoint-crashname -silence-passes -replace-funcs-with-null > /dev/null
+; RUN: llvm-dis %t-reduced-simplified.bc -o - | FileCheck --check-prefix=NUKE %s
+
+declare i32 @foo()
+declare i32 @crashing()
+declare dso_local i32 @bar()
+
+; NONUKE-NOT: @foo
+; NONUKE: declare void @crashing
+; NONUKE-NOT: @foo
+; NONUKE-LABEL: define void @test(
+; NONUKE-NEXT:    call void @crashing()
+; NONUKE-NEXT:    ret void
+
+; NUKE-NOT: @foo
+; NUKE-NOT: @crashing
+; NUKE-NOT: @foo
+; NUKE-LABEL: define void @test(
+; NUKE-NEXT:    %v2 = call i32 null()
+; NUKE-NEXT:    ret void
+
+define i32 @test(i32* %a, i8* %b) {
+    %v1 = call i32 @foo()
+    %v2 = call i32 @crashing()
+    %t = add i32 %v1, %v2
+    ret i32 %t
+}
diff --git a/llvm/tools/bugpoint-passes/TestPasses.cpp b/llvm/tools/bugpoint-passes/TestPasses.cpp
--- a/llvm/tools/bugpoint-passes/TestPasses.cpp
+++ b/llvm/tools/bugpoint-passes/TestPasses.cpp
@@ -185,3 +185,29 @@
     C("bugpoint-crashmetadata",
       "BugPoint Test Pass - Intentionally crash on "
       "fabs calls with fpmath metadata and an fadd as argument");
+
+namespace {
+class CrashOnCall : public FunctionPass {
+public:
+  static char ID; // Pass ID, replacement for typeid
+  CrashOnCall() : FunctionPass(ID) {}
+
+private:
+  void getAnalysisUsage(AnalysisUsage &AU) const override {
+    AU.setPreservesAll();
+  }
+
+  // Crash on any instructions using values name 'crashing'.
+  bool runOnFunction(Function &F) override {
+    for (Instruction &I : instructions(F))
+      if (isa<CallInst>(&I))
+        abort();
+    return false;
+  }
+};
+} // namespace
+
+char CrashOnCall::ID = 0;
+static RegisterPass<CrashOnCall>
+    D("bugpoint-crashname",
+      "BugPoint Test Pass - Intentionally crash on calls;");
diff --git a/llvm/tools/bugpoint/CrashDebugger.cpp b/llvm/tools/bugpoint/CrashDebugger.cpp
--- a/llvm/tools/bugpoint/CrashDebugger.cpp
+++ b/llvm/tools/bugpoint/CrashDebugger.cpp
@@ -262,9 +262,13 @@
   if (!ReplaceFuncsWithNull) {
     // Loop over and delete any functions which we aren't supposed to be playing
     // with...
-    for (Function &I : *M)
-      if (!I.isDeclaration() && !Functions.count(&I))
+    for (Function &I : make_early_inc_range(*M)) {
+      if (Functions.count(&I))
+        continue;
+      if (!I.isDeclaration()) {
         DeleteFunctionBody(&I);
+      }
+    }
   } else {
     std::vector<GlobalValue *> ToRemove;
     // First, remove aliases to functions we're about to purge.
@@ -290,7 +294,7 @@
     }
 
     for (Function &I : *M) {
-      if (!I.isDeclaration() && !Functions.count(&I)) {
+      if (!Functions.count(&I)) {
         PointerType *Ty = cast<PointerType>(I.getType());
         Constant *Replacement = ConstantPointerNull::get(Ty);
         I.replaceAllUsesWith(Replacement);
@@ -1198,7 +1202,6 @@
   // Now try to reduce the number of functions in the module to something small.
   std::vector<Function *> Functions;
   for (Function &F : BD.getProgram())
-    if (!F.isDeclaration())
       Functions.push_back(&F);
 
   if (Functions.size() > 1 && !BugpointIsInterrupted) {