lld-link: Use opt:noref by default in debug builds

[alex.telishev]

Summary

MSVC linker uses /opt:icf as default in release builds (no /DEBUG) and /opt:noref in debug builds. We should do the same

[ruiu]

lld/COFF/Driver.cpp

850–854

Instead of adding a new if, move line 760-766 here and set DoGC and DoICF to false in that if.

[alex.telishev]

Set DoGC and DoICF flags together with Debug

[ruiu]

LGTM

lld/COFF/Driver.cpp

844

It is a bit odd that you mentioned only /opt:noref. I'd probably write a comment:

// /debug implies /opt:noref and /opt:noicf. This is compatible with MSVC.

[ruiu]

Sorry, please add a test for this and upload a patch again.

[alex.telishev]

Fixed tests and added test for /DEBUG implying /opt:noref.

lld/COFF/Driver.cpp

void LinkerDriver::link(ArrayRef<const char *> ArgsArr) {
   // Handle /verbose
   if (Args.hasArg(OPT_verbose))
     Config->Verbose = true;
 
   // Handle /force or /force:unresolved
   if (Args.hasArg(OPT_force) || Args.hasArg(OPT_force_unresolved))
     Config->Force = true;
 
-  // Handle /debug
-  if (Args.hasArg(OPT_debug)) {
-    Config->Debug = true;
-    Config->DebugTypes =
-        Args.hasArg(OPT_debugtype)
-            ? parseDebugType(Args.getLastArg(OPT_debugtype)->getValue())
-            : getDefaultDebugType(Args);
-  }
-
   // Create a dummy PDB file to satisfy build sytem rules.
   if (auto *Arg = Args.getLastArg(OPT_pdb))
     Config->PDBPath = Arg->getValue();
 
   // Handle /noentry
   if (Args.hasArg(OPT_noentry)) {
     if (Args.hasArg(OPT_dll))
       Config->NoEntry = true;
void LinkerDriver::link(ArrayRef<const char *> ArgsArr) {
   // Handle /include
   for (auto *Arg : Args.filtered(OPT_incl))
     addUndefined(Arg->getValue());
 
   // Handle /implib
   if (auto *Arg = Args.getLastArg(OPT_implib))
     Config->Implib = Arg->getValue();
 
+  // Handle /debug
+  if (Args.hasArg(OPT_debug)) {
+    Config->Debug = true;
+    Config->DebugTypes =
+        Args.hasArg(OPT_debugtype)
+            ? parseDebugType(Args.getLastArg(OPT_debugtype)->getValue())
+            : getDefaultDebugType(Args);
+
+    // msvc linker uses /opt:noref by default in debug builds
+    Config->DoGC = false;
+    Config->DoICF = false;
+  }
+
   // Handle /opt
   for (auto *Arg : Args.filtered(OPT_opt)) {
     std::string Str = StringRef(Arg->getValue()).lower();
     SmallVector<StringRef, 1> Vec;
     StringRef(Str).split(Vec, ',');
     for (StringRef S : Vec) {
       if (S == "noref") {
         Config->DoGC = false;
         Config->DoICF = false;
         continue;
       }
       if (S == "icf" || StringRef(S).startswith("icf=")) {
         Config->DoICF = true;
         continue;

lld/test/COFF/icf-associative.test

 # RUN: yaml2obj < %s > %t.obj
 # RUN: lld-link /entry:foo /out:%t.exe /subsystem:console /include:bar \
-# RUN:   /debug /verbose %t.obj > %t.log 2>&1
+# RUN:   /debug /opt:icf /verbose %t.obj > %t.log 2>&1
 # RUN: FileCheck %s < %t.log
 
 # CHECK: Selected foo
 # CHECK:   Removed bar
 
 --- !COFF
 header:
   Machine:         IMAGE_FILE_MACHINE_AMD64

lld/test/COFF/icf-simple.test

 # RUN: yaml2obj < %s > %t.obj
 # RUN: lld-link /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
 
 # ICF: Selected foo
 # ICF:   Removed bar
 
 # RUN: lld-link /entry:foo /out:%t.exe /subsystem:console /include:bar \
 # RUN:   /verbose /opt:noicf %t.obj > %t.log 2>&1
 # RUN: FileCheck -check-prefix=NOICF %s < %t.log
 # RUN: lld-link /entry:foo /out:%t.exe /subsystem:console /include:bar \
 # RUN:   /verbose /opt:noref,noicf %t.obj > %t.log 2>&1
 # RUN: FileCheck -check-prefix=NOICF %s < %t.log
+# RUN: lld-link /entry:foo /out:%t.exe /subsystem:console /include:bar \
+# RUN:   /verbose /debug %t.obj > %t.log 2>&1
+# RUN: FileCheck -check-prefix=NOICF %s < %t.log
 
 # NOICF-NOT: Removed foo
 # NOICF-NOT: Removed bar
 
 --- !COFF
 header:
   Machine:         IMAGE_FILE_MACHINE_AMD64
   Characteristics: []

lld/test/COFF/pdb-global-gc.yaml

 # 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: lld-link %t.obj %t2.obj -debug -opt:ref -entry:main \
+# RUN:          -nodefaultlib -debug -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
 # info may refer to the __imp_ symbol still.
 
 # Compile this code with MSVC to regenerate the test case:
 #   extern char __declspec(dllimport) __wc_mb_cur;
 #   int discarded() { return __wc_mb_cur; }