diff --git a/llvm/test/tools/llvm-reduce/no-replace-intrinsic-callee-with-undef.ll b/llvm/test/tools/llvm-reduce/no-replace-intrinsic-callee-with-undef.ll
--- a/llvm/test/tools/llvm-reduce/no-replace-intrinsic-callee-with-undef.ll
+++ b/llvm/test/tools/llvm-reduce/no-replace-intrinsic-callee-with-undef.ll
@@ -3,11 +3,11 @@
 ; not replaced. The whole call instruction can be removed by instruction
 ; reduction instead.
 
-; RUN: llvm-reduce --test FileCheck --test-arg --check-prefixes=ALL,CHECK-INTERESTINGNESS --test-arg %s --test-arg --input-file %s -o %t 2> %t.log
+; RUN: llvm-reduce --delta-passes=functions,instructions --test FileCheck --test-arg --check-prefixes=ALL,CHECK-INTERESTINGNESS --test-arg %s --test-arg --input-file %s -o %t 2> %t.log
 ; RUN: FileCheck -implicit-check-not=uninteresting --check-prefixes=ALL,CHECK-FINAL %s < %t
 
 ; Check that the call is removed by instruction reduction passes
-; RUN: llvm-reduce --test FileCheck --test-arg --check-prefix=ALL --test-arg %s --test-arg --input-file %s -o %t
+; RUN: llvm-reduce --delta-passes=functions,instructions --test FileCheck --test-arg --check-prefix=ALL --test-arg %s --test-arg --input-file %s -o %t
 ; RUN: FileCheck -implicit-check-not=uninteresting --check-prefixes=ALL,CHECK-NOCALL %s < %t
 
 
diff --git a/llvm/test/tools/llvm-reduce/remove-all-of-multiple-args.ll b/llvm/test/tools/llvm-reduce/remove-all-of-multiple-args.ll
--- a/llvm/test/tools/llvm-reduce/remove-all-of-multiple-args.ll
+++ b/llvm/test/tools/llvm-reduce/remove-all-of-multiple-args.ll
@@ -1,4 +1,4 @@
-; RUN: llvm-reduce --test FileCheck --test-arg --check-prefixes=CHECK-ALL,CHECK-INTERESTINGNESS --test-arg %s --test-arg --input-file %s -o %t
+; RUN: llvm-reduce --delta-passes=arguments --test FileCheck --test-arg --check-prefixes=CHECK-ALL,CHECK-INTERESTINGNESS --test-arg %s --test-arg --input-file %s -o %t
 ; RUN: cat %t | FileCheck --check-prefixes=CHECK-ALL,CHECK-FINAL %s
 
 define i32 @t(i32 %a0, i32 %a1, i32 %a2) {
diff --git a/llvm/test/tools/llvm-reduce/remove-args-2.ll b/llvm/test/tools/llvm-reduce/remove-args-2.ll
--- a/llvm/test/tools/llvm-reduce/remove-args-2.ll
+++ b/llvm/test/tools/llvm-reduce/remove-args-2.ll
@@ -1,7 +1,7 @@
 ; Test that llvm-reduce can remove uninteresting function arguments from function definitions as well as their calls.
 ; This test checks that functions with different argument types are handled correctly
 ;
-; RUN: llvm-reduce --test FileCheck --test-arg --check-prefixes=CHECK-ALL,CHECK-INTERESTINGNESS --test-arg %s --test-arg --input-file %s -o %t
+; RUN: llvm-reduce --delta-passes=arguments --test FileCheck --test-arg --check-prefixes=CHECK-ALL,CHECK-INTERESTINGNESS --test-arg %s --test-arg --input-file %s -o %t
 ; RUN: FileCheck --check-prefixes=CHECK-ALL,CHECK-FINAL %s --input-file %t
 
 %struct.foo = type { %struct.foo*, i32, i32, i8* }
diff --git a/llvm/test/tools/llvm-reduce/remove-args-used-by-ret.ll b/llvm/test/tools/llvm-reduce/remove-args-used-by-ret.ll
--- a/llvm/test/tools/llvm-reduce/remove-args-used-by-ret.ll
+++ b/llvm/test/tools/llvm-reduce/remove-args-used-by-ret.ll
@@ -1,4 +1,4 @@
-; RUN: llvm-reduce --test FileCheck --test-arg --check-prefixes=CHECK-ALL,CHECK-INTERESTINGNESS --test-arg %s --test-arg --input-file %s -o %t
+; RUN: llvm-reduce --delta-passes=arguments --test FileCheck --test-arg --check-prefixes=CHECK-ALL,CHECK-INTERESTINGNESS --test-arg %s --test-arg --input-file %s -o %t
 ; RUN: cat %t | FileCheck --check-prefixes=CHECK-ALL,CHECK-FINAL %s
 
 ; We can't drop arguments if they are used by terminator instructions.
diff --git a/llvm/test/tools/llvm-reduce/remove-args.ll b/llvm/test/tools/llvm-reduce/remove-args.ll
--- a/llvm/test/tools/llvm-reduce/remove-args.ll
+++ b/llvm/test/tools/llvm-reduce/remove-args.ll
@@ -1,6 +1,6 @@
 ; Test that llvm-reduce can remove uninteresting function arguments from function definitions as well as their calls.
 ;
-; RUN: llvm-reduce --test %python --test-arg %p/Inputs/remove-args.py %s -o %t
+; RUN: llvm-reduce -delta-passes=arguments --test %python --test-arg %p/Inputs/remove-args.py %s -o %t
 ; RUN: cat %t | FileCheck -implicit-check-not=uninteresting %s
 
 ; CHECK: @interesting(i32 %interesting)
diff --git a/llvm/test/tools/llvm-reduce/remove-bbs-ret-nonvoid.ll b/llvm/test/tools/llvm-reduce/remove-bbs-ret-nonvoid.ll
--- a/llvm/test/tools/llvm-reduce/remove-bbs-ret-nonvoid.ll
+++ b/llvm/test/tools/llvm-reduce/remove-bbs-ret-nonvoid.ll
@@ -1,14 +1,14 @@
 ; Test that llvm-reduce inserts valid return instructions for functions with
 ; on-void return types.
 ;
-; RUN: llvm-reduce --test FileCheck --test-arg --check-prefixes=CHECK-INTERESTINGNESS --test-arg %s --test-arg --input-file %s -o %t
+; RUN: llvm-reduce --delta-passes=basic-blocks --test FileCheck --test-arg --check-prefixes=CHECK-INTERESTINGNESS --test-arg %s --test-arg --input-file %s -o %t
 ; RUN: cat %t | FileCheck %s
 
 ; CHECK-INTERESTINGNESS: interesting:
 ; CHECK-INTERESTINGNESS: interesting2:
 
 define i32 @main(i1 %c) {
-; CHECK-LABEL: define i32 @main() {
+; CHECK-LABEL: define i32 @main(i1 %c) {
 ; CHECK-LABEL: interesting:
 ; CHECK-NEXT:    br label %interesting2
 
diff --git a/llvm/test/tools/llvm-reduce/remove-bbs-unwinded-to.ll b/llvm/test/tools/llvm-reduce/remove-bbs-unwinded-to.ll
--- a/llvm/test/tools/llvm-reduce/remove-bbs-unwinded-to.ll
+++ b/llvm/test/tools/llvm-reduce/remove-bbs-unwinded-to.ll
@@ -1,4 +1,4 @@
-; RUN: llvm-reduce --test FileCheck --test-arg --check-prefixes=CHECK-ALL,CHECK-INTERESTINGNESS --test-arg %s --test-arg --input-file %s -o %t
+; RUN: llvm-reduce --delta-passes=basic-blocks --test FileCheck --test-arg --check-prefixes=CHECK-ALL,CHECK-INTERESTINGNESS --test-arg %s --test-arg --input-file %s -o %t
 ; RUN: cat %t | FileCheck --check-prefixes=CHECK-ALL,CHECK-FINAL %s
 
 declare i32 @maybe_throwing_callee()
diff --git a/llvm/test/tools/llvm-reduce/remove-bbs.ll b/llvm/test/tools/llvm-reduce/remove-bbs.ll
--- a/llvm/test/tools/llvm-reduce/remove-bbs.ll
+++ b/llvm/test/tools/llvm-reduce/remove-bbs.ll
@@ -1,7 +1,7 @@
 ; Test that llvm-reduce can remove uninteresting Basic Blocks, and remove them from instructions (i.e. SwitchInst, BranchInst and IndirectBrInst)
 ; Note: if an uninteresting BB is the default case for a switch, the instruction is removed altogether (since the default case cannot be replaced)
 ;
-; RUN: llvm-reduce --test %python --test-arg %p/Inputs/remove-bbs.py %s -o %t
+; RUN: llvm-reduce --delta-passes=basic-blocks --test %python --test-arg %p/Inputs/remove-bbs.py %s -o %t
 ; RUN: cat %t | FileCheck -implicit-check-not=uninteresting %s
 
 define void @main() {
diff --git a/llvm/test/tools/llvm-reduce/remove-funcs.ll b/llvm/test/tools/llvm-reduce/remove-funcs.ll
--- a/llvm/test/tools/llvm-reduce/remove-funcs.ll
+++ b/llvm/test/tools/llvm-reduce/remove-funcs.ll
@@ -1,7 +1,7 @@
 ; Test that llvm-reduce can remove uninteresting functions as well as
 ; their InstCalls.
 ;
-; RUN: llvm-reduce --test FileCheck --test-arg --check-prefixes=CHECK-ALL,CHECK-INTERESTINGNESS --test-arg %s --test-arg --input-file %s -o %t
+; RUN: llvm-reduce --delta-passes=functions,instructions --test FileCheck --test-arg --check-prefixes=CHECK-ALL,CHECK-INTERESTINGNESS --test-arg %s --test-arg --input-file %s -o %t
 ; RUN: cat %t | FileCheck -implicit-check-not=uninteresting --check-prefixes=CHECK-ALL,CHECK-FINAL %s
 
 define i32 @uninteresting1() {
diff --git a/llvm/test/tools/llvm-reduce/remove-function-arguments-of-funcs-used-in-blockaddress.ll b/llvm/test/tools/llvm-reduce/remove-function-arguments-of-funcs-used-in-blockaddress.ll
--- a/llvm/test/tools/llvm-reduce/remove-function-arguments-of-funcs-used-in-blockaddress.ll
+++ b/llvm/test/tools/llvm-reduce/remove-function-arguments-of-funcs-used-in-blockaddress.ll
@@ -1,4 +1,4 @@
-; RUN: llvm-reduce --test FileCheck --test-arg --check-prefixes=CHECK-ALL,CHECK-INTERESTINGNESS --test-arg %s --test-arg --input-file %s -o %t
+; RUN: llvm-reduce --delta-passes=arguments --test FileCheck --test-arg --check-prefixes=CHECK-ALL,CHECK-INTERESTINGNESS --test-arg %s --test-arg --input-file %s -o %t
 ; RUN: cat %t | FileCheck --check-prefixes=CHECK-ALL,CHECK-FINAL %s
 
 ; CHECK-INTERESTINGNESS: define void @func(
diff --git a/llvm/test/tools/llvm-reduce/remove-global-vars.ll b/llvm/test/tools/llvm-reduce/remove-global-vars.ll
--- a/llvm/test/tools/llvm-reduce/remove-global-vars.ll
+++ b/llvm/test/tools/llvm-reduce/remove-global-vars.ll
@@ -1,7 +1,7 @@
 ; Test that llvm-reduce can remove uninteresting Global Variables as well as
 ; their direct uses (which in turn are replaced with 'undef').
 
-; RUN: llvm-reduce --test FileCheck --test-arg --check-prefixes=CHECK-ALL,CHECK-INTERESTINGNESS --test-arg %s --test-arg --input-file %s -o %t
+; RUN: llvm-reduce --delta-passes=global-variables,global-initializers --test FileCheck --test-arg --check-prefixes=CHECK-ALL,CHECK-INTERESTINGNESS --test-arg %s --test-arg --input-file %s -o %t
 ; RUN: cat %t | FileCheck --check-prefixes=CHECK-ALL,CHECK-FINAL --implicit-check-not=uninteresting %s
 
 $interesting5 = comdat any
diff --git a/llvm/test/tools/llvm-reduce/remove-invoked-functions.ll b/llvm/test/tools/llvm-reduce/remove-invoked-functions.ll
--- a/llvm/test/tools/llvm-reduce/remove-invoked-functions.ll
+++ b/llvm/test/tools/llvm-reduce/remove-invoked-functions.ll
@@ -22,8 +22,8 @@
 define void @caller(i32 %arg) personality i8* bitcast (i32 (...)* @__gxx_personality_v0 to i8*) {
 ; CHECK-ALL: bb:
 bb:
-; CHECK-INTERESTINGNESS: %i0 = invoke i32
-; CHECK-FINAL: %i0 = invoke i32 bitcast (i32 ()* @maybe_throwing_callee to i32 (i32)*)(i32 %arg)
+; CHECK-INTERESTINGNESS: %i0 = invoke i32 {{.*}}@maybe_throwing_callee
+; CHECK-FINAL: %i0 = invoke i32 bitcast (i32 ()* @maybe_throwing_callee to i32 (i32)*)
 ; CHECK-ALL: to label %bb3 unwind label %bb1
   %i0 = invoke i32 @maybe_throwing_callee(i32 %arg)
           to label %bb3 unwind label %bb1
diff --git a/llvm/test/tools/llvm-reduce/remove-operands.ll b/llvm/test/tools/llvm-reduce/remove-operands.ll
new file mode 100644
--- /dev/null
+++ b/llvm/test/tools/llvm-reduce/remove-operands.ll
@@ -0,0 +1,20 @@
+; Test that llvm-reduce can reduce operands to their default values.
+;
+; RUN: llvm-reduce --delta-passes=operands --test FileCheck --test-arg --check-prefixes=CHECK-INTERESTINGNESS --test-arg %s --test-arg --input-file %s -o %t
+; RUN: cat %t | FileCheck %s
+
+; CHECK-INTERESTINGNESS: ret i32
+
+; CHECK-LABEL: define i32 @main() {
+define i32 @main() {
+
+; CHECK-LABEL: lb1:
+; CHECK-NEXT: br label %lb2
+lb1:
+  br label %lb2
+
+; CHECK-LABEL: lb2:
+; CHECK-NEXT: ret i32 undef
+lb2:
+  ret i32 10
+}
diff --git a/llvm/test/tools/llvm-reduce/remove-single-arg.ll b/llvm/test/tools/llvm-reduce/remove-single-arg.ll
--- a/llvm/test/tools/llvm-reduce/remove-single-arg.ll
+++ b/llvm/test/tools/llvm-reduce/remove-single-arg.ll
@@ -1,4 +1,4 @@
-; RUN: llvm-reduce --test FileCheck --test-arg --check-prefixes=CHECK-ALL,CHECK-INTERESTINGNESS --test-arg %s --test-arg --input-file %s -o %t
+; RUN: llvm-reduce --delta-passes=arguments --test FileCheck --test-arg --check-prefixes=CHECK-ALL,CHECK-INTERESTINGNESS --test-arg %s --test-arg --input-file %s -o %t
 ; RUN: cat %t | FileCheck --check-prefixes=CHECK-ALL,CHECK-FINAL %s
 
 define i32 @t(i32 %a0) {
diff --git a/llvm/tools/llvm-reduce/CMakeLists.txt b/llvm/tools/llvm-reduce/CMakeLists.txt
--- a/llvm/tools/llvm-reduce/CMakeLists.txt
+++ b/llvm/tools/llvm-reduce/CMakeLists.txt
@@ -28,6 +28,7 @@
   deltas/ReduceModuleData.cpp
   deltas/ReduceOperandBundles.cpp
   deltas/ReduceSpecialGlobals.cpp
+  deltas/ReduceOperands.cpp
   llvm-reduce.cpp
 
   DEPENDS
diff --git a/llvm/tools/llvm-reduce/DeltaManager.cpp b/llvm/tools/llvm-reduce/DeltaManager.cpp
--- a/llvm/tools/llvm-reduce/DeltaManager.cpp
+++ b/llvm/tools/llvm-reduce/DeltaManager.cpp
@@ -27,6 +27,7 @@
 #include "deltas/ReduceMetadata.h"
 #include "deltas/ReduceModuleData.h"
 #include "deltas/ReduceOperandBundles.h"
+#include "deltas/ReduceOperands.h"
 #include "deltas/ReduceSpecialGlobals.h"
 #include "llvm/Support/CommandLine.h"
 
@@ -49,6 +50,7 @@
   DELTA_PASS("metadata", reduceMetadataDeltaPass)                              \
   DELTA_PASS("arguments", reduceArgumentsDeltaPass)                            \
   DELTA_PASS("instructions", reduceInstructionsDeltaPass)                      \
+  DELTA_PASS("operands", reduceOperandsDeltaPass)                              \
   DELTA_PASS("operand-bundles", reduceOperandBundesDeltaPass)                  \
   DELTA_PASS("attributes", reduceAttributesDeltaPass)                          \
   DELTA_PASS("module-data", reduceModuleDataDeltaPass)
diff --git a/llvm/tools/llvm-reduce/deltas/ReduceOperands.h b/llvm/tools/llvm-reduce/deltas/ReduceOperands.h
new file mode 100755
--- /dev/null
+++ b/llvm/tools/llvm-reduce/deltas/ReduceOperands.h
@@ -0,0 +1,22 @@
+//===- ReduceOperands.h - Specialized Delta Pass --------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements a function to reduce operands to undef.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_TOOLS_LLVM_REDUCE_DELTAS_REDUCEOPERANDS_H
+#define LLVM_TOOLS_LLVM_REDUCE_DELTAS_REDUCEOPERANDS_H
+
+#include "Delta.h"
+
+namespace llvm {
+void reduceOperandsDeltaPass(TestRunner &Test);
+} // namespace llvm
+
+#endif
diff --git a/llvm/tools/llvm-reduce/deltas/ReduceOperands.cpp b/llvm/tools/llvm-reduce/deltas/ReduceOperands.cpp
new file mode 100755
--- /dev/null
+++ b/llvm/tools/llvm-reduce/deltas/ReduceOperands.cpp
@@ -0,0 +1,74 @@
+//===- ReduceOperands.cpp - Specialized Delta Pass ------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements a function to reduce operands to undef.
+//
+//===----------------------------------------------------------------------===//
+
+#include "ReduceOperands.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/InstIterator.h"
+
+using namespace llvm;
+
+/// Returns if the given operand is undef.
+static bool operandIsUndefValue(Use &Op) {
+  if (auto *C = dyn_cast<Constant>(Op)) {
+    return isa<UndefValue>(C);
+  }
+  return false;
+}
+
+/// Returns if an operand can be reduced to undef.
+/// TODO: make this logic check what types are reducible rather than
+/// check what types that are not reducible.
+static bool canReduceOperand(Use &Op) {
+  auto *Ty = Op->getType();
+  // Can't reduce labels to undef
+  return !Ty->isLabelTy() && !operandIsUndefValue(Op);
+}
+
+/// Sets Operands to undef.
+static void extractOperandsFromModule(std::vector<Chunk> ChunksToKeep,
+                                      Module *Program) {
+  Oracle O(ChunksToKeep);
+
+  // Extract Operands from the module.
+  for (auto &F : Program->functions()) {
+    for (auto &I : instructions(&F)) {
+      for (auto &Op : I.operands()) {
+        // Filter Operands then set to undef.
+        if (canReduceOperand(Op) && !O.shouldKeep()) {
+          auto *Ty = Op->getType();
+          Op.set(UndefValue::get(Ty));
+        }
+      }
+    }
+  }
+}
+
+/// Counts the amount of operands in the module that can be reduced.
+static int countOperands(Module *Program) {
+  int Count = 0;
+  for (auto &F : Program->functions()) {
+    for (auto &I : instructions(&F)) {
+      for (auto &Op : I.operands()) {
+        if (canReduceOperand(Op)) {
+          Count++;
+        }
+      }
+    }
+  }
+  return Count;
+}
+
+void llvm::reduceOperandsDeltaPass(TestRunner &Test) {
+  errs() << "*** Reducing Operands...\n";
+  int Count = countOperands(Test.getProgram());
+  runDeltaPass(Test, Count, extractOperandsFromModule);
+}
diff --git a/llvm/utils/gn/secondary/llvm/tools/llvm-reduce/BUILD.gn b/llvm/utils/gn/secondary/llvm/tools/llvm-reduce/BUILD.gn
--- a/llvm/utils/gn/secondary/llvm/tools/llvm-reduce/BUILD.gn
+++ b/llvm/utils/gn/secondary/llvm/tools/llvm-reduce/BUILD.gn
@@ -26,6 +26,7 @@
     "deltas/ReduceModuleData.cpp",
     "deltas/ReduceOperandBundles.cpp",
     "deltas/ReduceSpecialGlobals.cpp",
+    "deltas/ReduceOperands.cpp",
     "llvm-reduce.cpp",
   ]
 }