Index: llvm/tools/llvm-reduce/TestRunner.h
===================================================================
--- llvm/tools/llvm-reduce/TestRunner.h
+++ llvm/tools/llvm-reduce/TestRunner.h
@@ -29,7 +29,8 @@
   TestRunner(StringRef TestName, ArrayRef<std::string> TestArgs,
              std::unique_ptr<ReducerWorkItem> Program,
              std::unique_ptr<TargetMachine> TM, const char *ToolName,
-             StringRef OutputFilename, bool InputIsBitcode, bool OutputBitcode);
+             StringRef OutputFilename, bool InputIsBitcode, bool OutputBitcode,
+             bool PreserveDebugEnvironment);
 
   /// Runs the interesting-ness test for the specified file
   /// @returns 0 if test was successful, 1 if otherwise
@@ -59,6 +60,7 @@
   StringRef OutputFilename;
   const bool InputIsBitcode;
   bool EmitBitcode;
+  const bool PreserveDebugEnvironment;
 };
 
 } // namespace llvm
Index: llvm/tools/llvm-reduce/TestRunner.cpp
===================================================================
--- llvm/tools/llvm-reduce/TestRunner.cpp
+++ llvm/tools/llvm-reduce/TestRunner.cpp
@@ -22,10 +22,11 @@
                        std::unique_ptr<ReducerWorkItem> Program,
                        std::unique_ptr<TargetMachine> TM, const char *ToolName,
                        StringRef OutputName, bool InputIsBitcode,
-                       bool OutputBitcode)
+                       bool OutputBitcode, bool PreserveDebugEnvironment)
     : TestName(TestName), ToolName(ToolName), Program(std::move(Program)),
       TM(std::move(TM)), OutputFilename(OutputName),
-      InputIsBitcode(InputIsBitcode), EmitBitcode(OutputBitcode) {
+      InputIsBitcode(InputIsBitcode), EmitBitcode(OutputBitcode),
+      PreserveDebugEnvironment(PreserveDebugEnvironment) {
   assert(this->Program && "Initialized with null program?");
 
   TestArgs.push_back(TestName); // argv[0]
@@ -36,6 +37,11 @@
     StringRef()};
 static constexpr std::array<std::optional<StringRef>, 3> NullRedirects;
 
+static constexpr std::array<StringRef, 2> DebugEnvironmentVars = {
+  "LLVM_DISABLE_CRASH_REPORT=1",
+  "LLVM_DISABLE_SYMBOLIZATION=1"
+};
+
 /// Runs the interestingness test, passes file to be tested as first argument
 /// and other specified test arguments after that.
 int TestRunner::run(StringRef Filename) const {
@@ -44,10 +50,15 @@
 
   std::string ErrMsg;
 
-  int Result =
-      sys::ExecuteAndWait(TestName, ExecArgs, /*Env=*/std::nullopt,
-                          Verbose ? DefaultRedirects : NullRedirects,
-                          /*SecondsToWait=*/0, /*MemoryLimit=*/0, &ErrMsg);
+  const std::optional<ArrayRef<StringRef>> Env =
+      PreserveDebugEnvironment ? std::nullopt
+                               : std::make_optional(DebugEnvironmentVars);
+
+  int Result = sys::ExecuteAndWait(
+      TestName, ExecArgs,
+      /*Env=*/Env,
+      /*Redirects=*/Verbose ? DefaultRedirects : NullRedirects,
+      /*SecondsToWait=*/0, /*MemoryLimit=*/0, &ErrMsg);
 
   if (Result < 0) {
     Error E = make_error<StringError>("Error running interesting-ness test: " +
Index: llvm/tools/llvm-reduce/llvm-reduce.cpp
===================================================================
--- llvm/tools/llvm-reduce/llvm-reduce.cpp
+++ llvm/tools/llvm-reduce/llvm-reduce.cpp
@@ -26,10 +26,6 @@
 #include <system_error>
 #include <vector>
 
-#ifdef _WIN32
-#include <windows.h>
-#endif
-
 using namespace llvm;
 
 cl::OptionCategory LLVMReduceOptions("llvm-reduce options");
@@ -109,15 +105,6 @@
 /// output clutter and avoid potentially slow symbolization.
 static void disableEnvironmentDebugFeatures() {
   sys::Process::PreventCoreFiles();
-
-  // TODO: Copied from not. Should have a wrapper around setenv.
-#ifdef _WIN32
-  SetEnvironmentVariableA("LLVM_DISABLE_CRASH_REPORT", "1");
-  SetEnvironmentVariableA("LLVM_DISABLE_SYMBOLIZATION", "1");
-#else
-  setenv("LLVM_DISABLE_CRASH_REPORT", "1", /*overwrite=*/1);
-  setenv("LLVM_DISABLE_SYMBOLIZATION", "1", /*overwrite=*/1);
-#endif
 }
 
 static std::pair<StringRef, bool> determineOutputType(bool IsMIR,
@@ -193,7 +180,7 @@
   // Initialize test environment
   TestRunner Tester(TestFilename, TestArguments, std::move(OriginalProgram),
                     std::move(TM), Argv[0], OutputFilename, InputIsBitcode,
-                    OutputBitcode);
+                    OutputBitcode, PreserveDebugEnvironment);
 
   // This parses and writes out the testcase into a temporary file copy for the
   // test, rather than evaluating the source IR directly. This is for the