[clang] [Clang][Driver] Revise Cygwin ToolChain to call linker directly (PR #147960)

[Tomohiro Kashiwada via cfe-commits]

================
@@ -107,3 +110,282 @@ void Cygwin::AddClangSystemIncludeArgs(const ArgList &DriverArgs,
   addExternCSystemInclude(DriverArgs, CC1Args, SysRoot + "/usr/include");
   addExternCSystemInclude(DriverArgs, CC1Args, SysRoot + "/usr/include/w32api");
 }
+
+void cygwin::Linker::ConstructJob(Compilation &C, const JobAction &JA,
+                                  const InputInfo &Output,
+                                  const InputInfoList &Inputs,
+                                  const ArgList &Args,
+                                  const char *LinkingOutput) const {
+  const auto &ToolChain = getToolChain();
+  const Driver &D = ToolChain.getDriver();
+
+  const bool IsStatic = Args.hasArg(options::OPT_static);
+
+  ArgStringList CmdArgs;
+
+  // Silence warning for "clang -g foo.o -o foo"
+  Args.ClaimAllArgs(options::OPT_g_Group);
+  // and "clang -emit-llvm foo.o -o foo"
+  Args.ClaimAllArgs(options::OPT_emit_llvm);
+  // and for "clang -w foo.o -o foo". Other warning options are already
+  // handled somewhere else.
+  Args.ClaimAllArgs(options::OPT_w);
+
+  if (!D.SysRoot.empty())
+    CmdArgs.push_back(Args.MakeArgString("--sysroot=" + D.SysRoot));
+
+  if (Args.hasArg(options::OPT_s))
+    CmdArgs.push_back("-s");
+
+  CmdArgs.push_back("-m");
+  switch (ToolChain.getArch()) {
+  case llvm::Triple::x86:
+    CmdArgs.push_back("i386pe");
+    break;
+  case llvm::Triple::x86_64:
+    CmdArgs.push_back("i386pep");
+    break;
+  case llvm::Triple::arm:
+  case llvm::Triple::thumb:
+    // FIXME: this is incorrect for WinCE
+    CmdArgs.push_back("thumb2pe");
+    break;
+  case llvm::Triple::aarch64:
+    if (Args.hasArg(options::OPT_marm64x))
+      CmdArgs.push_back("arm64xpe");
+    else if (ToolChain.getEffectiveTriple().isWindowsArm64EC())
+      CmdArgs.push_back("arm64ecpe");
+    else
+      CmdArgs.push_back("arm64pe");
+    break;
+  case llvm::Triple::mipsel:
+    CmdArgs.push_back("mipspe");
+    break;
+  default:
+    D.Diag(diag::err_target_unknown_triple)
+        << ToolChain.getEffectiveTriple().str();
+  }
+
+  Arg *SubsysArg =
+      Args.getLastArg(options::OPT_mwindows, options::OPT_mconsole);
+  if (SubsysArg && SubsysArg->getOption().matches(options::OPT_mwindows)) {
+    CmdArgs.push_back("--subsystem");
+    CmdArgs.push_back("windows");
+  } else if (SubsysArg &&
+             SubsysArg->getOption().matches(options::OPT_mconsole)) {
+    CmdArgs.push_back("--subsystem");
+    CmdArgs.push_back("console");
+  }
+
+  CmdArgs.push_back("--wrap=_Znwm");
+  CmdArgs.push_back("--wrap=_Znam");
+  CmdArgs.push_back("--wrap=_ZdlPv");
+  CmdArgs.push_back("--wrap=_ZdaPv");
+  CmdArgs.push_back("--wrap=_ZnwmRKSt9nothrow_t");
+  CmdArgs.push_back("--wrap=_ZnamRKSt9nothrow_t");
+  CmdArgs.push_back("--wrap=_ZdlPvRKSt9nothrow_t");
+  CmdArgs.push_back("--wrap=_ZdaPvRKSt9nothrow_t");
----------------
kikairoya wrote:

`GlobalDecl` isn't accessible from this context. The `Driver` component can reference only the `Basic` component.

However, I found a way to see what `size_t` does mean on target triple (see diff).
<details>

<summary>diff</summary>

```diff
diff --git a/clang/lib/Driver/ToolChains/Cygwin.cpp b/clang/lib/Driver/ToolChains/Cygwin.cpp
index 079911b0f0ac..e2561172d386 100644
--- a/clang/lib/Driver/ToolChains/Cygwin.cpp
+++ b/clang/lib/Driver/ToolChains/Cygwin.cpp
@@ -7,6 +7,7 @@
 //===----------------------------------------------------------------------===//

 #include "Cygwin.h"
+#include "clang/Basic/TargetInfo.h"
 #include "clang/Config/config.h"
 #include "clang/Driver/CommonArgs.h"
 #include "clang/Driver/Compilation.h"
@@ -177,24 +178,32 @@ void cygwin::Linker::ConstructJob(Compilation &C, const JobAction &JA,
     CmdArgs.push_back("console");
   }

-  if (ToolChain.getTriple().isArch32Bit()) {
-    CmdArgs.push_back("--wrap=_Znwj");
-    CmdArgs.push_back("--wrap=_Znaj");
-    CmdArgs.push_back("--wrap=_ZdlPv");
-    CmdArgs.push_back("--wrap=_ZdaPv");
-    CmdArgs.push_back("--wrap=_ZnwjRKSt9nothrow_t");
-    CmdArgs.push_back("--wrap=_ZnajRKSt9nothrow_t");
-    CmdArgs.push_back("--wrap=_ZdlPvRKSt9nothrow_t");
-    CmdArgs.push_back("--wrap=_ZdaPvRKSt9nothrow_t");
-  } else {
-    CmdArgs.push_back("--wrap=_Znwm");
-    CmdArgs.push_back("--wrap=_Znam");
-    CmdArgs.push_back("--wrap=_ZdlPv");
-    CmdArgs.push_back("--wrap=_ZdaPv");
-    CmdArgs.push_back("--wrap=_ZnwmRKSt9nothrow_t");
-    CmdArgs.push_back("--wrap=_ZnamRKSt9nothrow_t");
-    CmdArgs.push_back("--wrap=_ZdlPvRKSt9nothrow_t");
-    CmdArgs.push_back("--wrap=_ZdaPvRKSt9nothrow_t");
+  auto TI = targets::AllocateTarget(ToolChain.getTriple(), {});
+  const auto TypeChar = [&]() {
+    switch (TI->getSizeType()) {
+    case TransferrableTargetInfo::UnsignedShort:
+      return 't';
+    case TransferrableTargetInfo::UnsignedInt:
+      return 'j';
+    case TransferrableTargetInfo::UnsignedLong:
+      return 'm';
+    case TransferrableTargetInfo::UnsignedLongLong:
+      return 'y';
+    default:
+      llvm_unreachable("Invalid SizeType");
+    }
+  }();
+  const auto *const LabelPrefix = TI->getUserLabelPrefix();
+  std::string WrapPrefix = "--wrap=";
+  if (LabelPrefix)
+    WrapPrefix += LabelPrefix;
+  for (std::string S : {"_Znw%", "_Zna%", "_ZdlPv", "_ZdaPv",
+                        "_Znw%RKSt9nothrow_t", "_Zna%RKSt9nothrow_t",
+                        "_ZdlPvRKSt9nothrow_t", "_ZdaPvRKSt9nothrow_t"}) {
+    auto Pos = S.find('%');
+    if (Pos != S.npos)
+      S[Pos] = TypeChar;
+    CmdArgs.push_back(Args.MakeArgString(WrapPrefix + S));
   }

   if (Args.hasArg(options::OPT_mdll))
```
</details>

BTW, `gcc -m32` doesn't wrap `new` properly (perhaps the old i686-native gcc can?) and the different mangling rule between `new` and `delete` is found from `libstdxx_wrapper.cc` in `cygwin1.dll`.

```
$ echo 'int main() { auto p = new int(3); delete p; }' | g++ -m64 -xc++ - -nostartfiles -nodefaultlibs -Wl,--no-demangle,--entry, -shared -fno-sized-deallocation
/usr/lib/gcc/x86_64-pc-cygwin/16/../../../../x86_64-pc-cygwin/bin/ld: /tmp/ccc30TZw.o:<stdin>:(.text+0x9): undefined reference to `__main'
/usr/lib/gcc/x86_64-pc-cygwin/16/../../../../x86_64-pc-cygwin/bin/ld: /tmp/ccc30TZw.o:<stdin>:(.text+0x13): undefined reference to `__wrap__Znwm'
/usr/lib/gcc/x86_64-pc-cygwin/16/../../../../x86_64-pc-cygwin/bin/ld: /tmp/ccc30TZw.o:<stdin>:(.text+0x2e): undefined reference to `__wrap__ZdlPv'
/usr/lib/gcc/x86_64-pc-cygwin/16/../../../../x86_64-pc-cygwin/bin/ld: /tmp/ccc30TZw.o:<stdin>:(.text+0x3f): undefined reference to `__wrap__ZdlPv'
collect2: エラー: ld はステータス 1 で終了しました


$ echo 'int main() { auto p = new int(3); delete p; }' | g++ -m32 -xc++ - -nostartfiles -nodefaultlibs -Wl,--no-demangle,--entry, -shared -fno-sized-deallocation
/usr/lib/gcc/x86_64-pc-cygwin/16/../../../../x86_64-pc-cygwin/bin/ld: /tmp/ccAA6tBm.o:<stdin>:(.text+0x7): undefined reference to `___main'
/usr/lib/gcc/x86_64-pc-cygwin/16/../../../../x86_64-pc-cygwin/bin/ld: /tmp/ccAA6tBm.o:<stdin>:(.text+0x13): undefined reference to `__Znwj'
/usr/lib/gcc/x86_64-pc-cygwin/16/../../../../x86_64-pc-cygwin/bin/ld: /tmp/ccAA6tBm.o:<stdin>:(.text+0x2d): undefined reference to `___wrap__ZdlPv'
/usr/lib/gcc/x86_64-pc-cygwin/16/../../../../x86_64-pc-cygwin/bin/ld: /tmp/ccAA6tBm.o:<stdin>:(.text+0x3c): undefined reference to `___wrap__ZdlPv'
collect2: エラー: ld はステータス 1 で終了しました
```


https://github.com/llvm/llvm-project/pull/147960