Index: llvm/include/llvm/InterfaceStub/IFSHandler.h
===================================================================
--- llvm/include/llvm/InterfaceStub/IFSHandler.h
+++ llvm/include/llvm/InterfaceStub/IFSHandler.h
@@ -51,9 +51,6 @@
 void stripIFSTarget(IFSStub &Stub, bool StripTriple, bool StripArch,
                     bool StripEndianness, bool StripBitWidth);
 
-/// Strips symbols from IFS symbol table that are undefined.
-void stripIFSUndefinedSymbols(IFSStub &Stub);
-
 /// Parse llvm triple string into a IFSTarget struct.
 IFSTarget parseTriple(StringRef TripleStr);
 
Index: llvm/lib/InterfaceStub/IFSHandler.cpp
===================================================================
--- llvm/lib/InterfaceStub/IFSHandler.cpp
+++ llvm/lib/InterfaceStub/IFSHandler.cpp
@@ -327,13 +327,3 @@
     Stub.Target.ObjectFormat.reset();
   }
 }
-
-void ifs::stripIFSUndefinedSymbols(IFSStub &Stub) {
-  for (auto Iter = Stub.Symbols.begin(); Iter != Stub.Symbols.end();) {
-    if (Iter->Undefined) {
-      Iter = Stub.Symbols.erase(Iter);
-    } else {
-      Iter++;
-    }
-  }
-}
Index: llvm/test/tools/llvm-ifs/preserve.test
===================================================================
--- /dev/null
+++ llvm/test/tools/llvm-ifs/preserve.test
@@ -0,0 +1,26 @@
+## Test --preserve flag
+
+# RUN: llvm-ifs --input-format=IFS --output-ifs=- --strip-undefined \
+# RUN: --preserve='keep_*' --preserve='diff_pattern_keep' %s | FileCheck %s
+
+# RUN: not llvm-ifs --input-format=IFS --output-ifs=- --preserve='[' %s 2>&1 | \
+# RUN: FileCheck %s --check-prefix=BAD-GLOB
+
+# BAD-GLOB: error: invalid glob pattern: [
+
+--- !ifs-v1
+SoName: somelib.so
+IfsVersion: 3.0
+Symbols:
+  - { Name: diff_pattern_keep, Type: Func, Undefined: true }
+  - { Name: dont_keep, Type: Func, Undefined: true }
+  - { Name: keep_1, Type: Func, Undefined: true }
+  - { Name: keep_2, Type: Func, Undefined: true }
+  - { Name: no_match_not_undef, Type: Func }
+...
+
+# CHECK:        - { Name: diff_pattern_keep, Type: Func, Undefined: true }
+# CHECK-NOT:    - { Name: dont_keep, Type: Func, Undefined: true }
+# CHECK-NEXT:   - { Name: keep_1, Type: Func, Undefined: true }
+# CHECK-NEXT:   - { Name: keep_2, Type: Func, Undefined: true }
+# CHECK-NEXT:   - { Name: no_match_not_undef, Type: Func }
Index: llvm/tools/llvm-ifs/llvm-ifs.cpp
===================================================================
--- llvm/tools/llvm-ifs/llvm-ifs.cpp
+++ llvm/tools/llvm-ifs/llvm-ifs.cpp
@@ -7,6 +7,7 @@
 //===-----------------------------------------------------------------------===/
 
 #include "ErrorCollector.h"
+#include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/ADT/StringSwitch.h"
 #include "llvm/ADT/Triple.h"
@@ -19,6 +20,7 @@
 #include "llvm/Support/Errc.h"
 #include "llvm/Support/Error.h"
 #include "llvm/Support/FileOutputBuffer.h"
+#include "llvm/Support/GlobPattern.h"
 #include "llvm/Support/MemoryBuffer.h"
 #include "llvm/Support/Path.h"
 #include "llvm/Support/VersionTuple.h"
@@ -28,6 +30,7 @@
 #include "llvm/TextAPI/InterfaceFile.h"
 #include "llvm/TextAPI/TextAPIReader.h"
 #include "llvm/TextAPI/TextAPIWriter.h"
+#include <functional>
 #include <set>
 #include <string>
 #include <vector>
@@ -103,6 +106,11 @@
     StripUndefined("strip-undefined",
                    cl::desc("Strip undefined symbols from IFS output"),
                    cl::cat(IfsCategory));
+cl::list<std::string>
+    PreserveSyms("preserve",
+                 cl::desc("Keep symbols which might otherwise be removed by "
+                          "--strip-undefined. Can be specified multiple times"),
+                 cl::cat(IfsCategory));
 
 cl::opt<std::string>
     SoName("soname",
@@ -287,6 +295,31 @@
   return Error::success();
 }
 
+static Error stripSyms(IFSStub &Stub) {
+  std::function<bool(const IFSSymbol &)> Filter = [](const IFSSymbol &) {
+    return false;
+  };
+
+  if (StripUndefined) {
+    Filter = [Filter](const IFSSymbol &Sym) {
+      return Sym.Undefined || Filter(Sym);
+    };
+  }
+
+  for (StringRef Glob : PreserveSyms) {
+    Expected<GlobPattern> PatternOrErr = GlobPattern::create(Glob);
+    if (!PatternOrErr)
+      return PatternOrErr.takeError();
+    Filter = [Pattern = *PatternOrErr, Filter](const IFSSymbol &Sym) {
+      return !Pattern.match(Sym.Name) && Filter(Sym);
+    };
+  }
+
+  llvm::erase_if(Stub.Symbols, Filter);
+
+  return Error::success();
+}
+
 int main(int argc, char *argv[]) {
   // Parse arguments.
   cl::HideUnrelatedOptions({&IfsCategory, &getColorCategory()});
@@ -473,8 +506,8 @@
         stripIFSTarget(Stub, StripIFSTarget, StripIFSArch,
                        StripIFSEndiannessWidth, StripIFSBitWidth);
       }
-      if (StripUndefined)
-        stripIFSUndefinedSymbols(Stub);
+      if (Error E = stripSyms(Stub))
+        fatalError(std::move(E));
       Error IFSWriteError = writeIFS(OutputFilePath.getValue(), Stub);
       if (IFSWriteError)
         fatalError(std::move(IFSWriteError));
@@ -525,8 +558,8 @@
         stripIFSTarget(Stub, StripIFSTarget, StripIFSArch,
                        StripIFSEndiannessWidth, StripIFSBitWidth);
       }
-      if (StripUndefined)
-        stripIFSUndefinedSymbols(Stub);
+      if (Error E = stripSyms(Stub))
+        fatalError(std::move(E));
       Error IFSWriteError = writeIFS(OutputIFSFilePath.getValue(), Stub);
       if (IFSWriteError)
         fatalError(std::move(IFSWriteError));