Index: lld/COFF/Driver.cpp
===================================================================
--- lld/COFF/Driver.cpp
+++ lld/COFF/Driver.cpp
@@ -896,7 +896,12 @@
   if (auto *Arg = Args.getLastArg(OPT_implib))
     Config->Implib = Arg->getValue();
 
-  // Handle /opt
+  // Handle /opt. Disable GC and ICF if /debug is specified and no /opt flag is
+  // specified.
+  if (Args.hasArg(OPT_debug)) {
+    Config->DoGC = false;
+    Config->DoICF = false;
+  }
   for (auto *Arg : Args.filtered(OPT_opt)) {
     std::string Str = StringRef(Arg->getValue()).lower();
     SmallVector<StringRef, 1> Vec;
@@ -907,7 +912,12 @@
         Config->DoICF = false;
         continue;
       }
+      if (S == "ref") {
+        Config->DoGC = true;
+        continue;
+      }
       if (S == "icf" || S.startswith("icf=")) {
+        Config->DoGC = true;
         Config->DoICF = true;
         continue;
       }
@@ -935,7 +945,7 @@
           error("/opt:lldltopartitions: invalid partition count: " + N);
         continue;
       }
-      if (S != "ref" && S != "lbr" && S != "nolbr")
+      if (S != "lbr" && S != "nolbr")
         error("/opt: unknown option: " + S);
     }
   }
Index: lld/test/COFF/icf-associative.test
===================================================================
--- lld/test/COFF/icf-associative.test
+++ lld/test/COFF/icf-associative.test
@@ -1,5 +1,5 @@
 # RUN: yaml2obj < %s > %t.obj
-# RUN: lld-link /entry:foo /out:%t.exe /subsystem:console /include:bar \
+# RUN: lld-link /opt:icf /entry:foo /out:%t.exe /subsystem:console /include:bar \
 # RUN:   /debug /verbose %t.obj > %t.log 2>&1
 # RUN: FileCheck %s < %t.log
 
Index: lld/test/COFF/icf-simple.test
===================================================================
--- lld/test/COFF/icf-simple.test
+++ lld/test/COFF/icf-simple.test
@@ -1,5 +1,5 @@
 # RUN: yaml2obj < %s > %t.obj
-# RUN: lld-link /entry:foo /out:%t.exe /subsystem:console /include:bar \
+# RUN: lld-link /opt:icf /entry:foo /out:%t.exe /subsystem:console /include:bar \
 # RUN:   /verbose %t.obj > %t.log 2>&1
 # RUN: FileCheck -check-prefix=ICF %s < %t.log
 
Index: lld/test/COFF/pdb-global-gc.yaml
===================================================================
--- lld/test/COFF/pdb-global-gc.yaml
+++ lld/test/COFF/pdb-global-gc.yaml
@@ -1,7 +1,7 @@
 # RUN: yaml2obj %s -o %t.obj
 # RUN: llvm-mc %S/Inputs/pdb-global-gc.s -triple x86_64-windows-msvc -filetype=obj -o %t2.obj
 # RUN: lld-link %t.obj %t2.obj -debug -entry:main \
-# RUN:          -nodefaultlib -debug -out:%t.exe -pdb:%t.pdb -verbose
+# RUN:          -nodefaultlib -opt:ref -out:%t.exe -pdb:%t.pdb -verbose
 # RUN: llvm-pdbutil dump -symbols -globals %t.pdb | FileCheck %s
 
 # This tests the case where an __imp_ chunk is discarded by linker GC. The debug
Index: lld/test/COFF/pdb-import-gc.yaml
===================================================================
--- lld/test/COFF/pdb-import-gc.yaml
+++ lld/test/COFF/pdb-import-gc.yaml
@@ -1,6 +1,6 @@
 # RUN: yaml2obj %s -o %t.obj
 # RUN: lld-link %t.obj %S/Inputs/pdb-import-gc.lib -debug -entry:main \
-# RUN:          -nodefaultlib -debug -out:%t.exe -pdb:%t.pdb
+# RUN:          -nodefaultlib -opt:ref -out:%t.exe -pdb:%t.pdb
 # RUN: llvm-pdbutil dump -globals -symbols %t.pdb | FileCheck %s
 
 # This tests the case where an __imp_ chunk is discarded by linker GC. The debug