Revert "[Driver][AVR] Fix warn_drv_avr_stdlib_not_linked condition"

This reverts commit 16524d2f1b.

The test caused some warnings when avr-gcc was not installed.

clang/lib/Driver/ToolChains/AVR.cpp

@@ -366,20 +366,50 @@ const StringRef PossibleAVRLibcLocations[] = {
 /// AVR Toolchain
 AVRToolChain::AVRToolChain(const Driver &D, const llvm::Triple &Triple,
                            const ArgList &Args)
-    : Generic_ELF(D, Triple, Args) {
+    : Generic_ELF(D, Triple, Args), LinkStdlib(false) {
   GCCInstallation.init(Triple, Args);
 
   // Only add default libraries if the user hasn't explicitly opted out.
   if (!Args.hasArg(options::OPT_nostdlib) &&
-      !Args.hasArg(options::OPT_nodefaultlibs)) {
+      !Args.hasArg(options::OPT_nodefaultlibs) &&
-    if (GCCInstallation.isValid()) {
+      !Args.hasArg(options::OPT_c /* does not apply when not linking */)) {
-      GCCInstallPath = GCCInstallation.getInstallPath();
+    std::string CPU = getCPUName(D, Args, Triple);
-      std::string GCCParentPath(GCCInstallation.getParentLibPath());
+
-      getProgramPaths().push_back(GCCParentPath + "/../bin");
+    if (CPU.empty()) {
+      // We cannot link any standard libraries without an MCU specified.
+      D.Diag(diag::warn_drv_avr_mcu_not_specified);
     } else {
+      Optional<StringRef> FamilyName = GetMCUFamilyName(CPU);
+      Optional<std::string> AVRLibcRoot = findAVRLibcInstallation();
+
+      if (!FamilyName.hasValue()) {
+        // We do not have an entry for this CPU in the family
+        // mapping table yet.
+        D.Diag(diag::warn_drv_avr_family_linking_stdlibs_not_implemented)
+            << CPU;
+      } else if (!GCCInstallation.isValid()) {
+        // No avr-gcc found and so no runtime linked.
         D.Diag(diag::warn_drv_avr_gcc_not_found);
+      } else if (!AVRLibcRoot.hasValue()) {
+        // No avr-libc found and so no runtime linked.
+        D.Diag(diag::warn_drv_avr_libc_not_found);
+      } else { // We have enough information to link stdlibs
+        std::string GCCRoot(GCCInstallation.getInstallPath());
+        std::string GCCParentPath(GCCInstallation.getParentLibPath());
+        std::string LibcRoot = AVRLibcRoot.getValue();
+        std::string SubPath = GetMCUSubPath(CPU);
+
+        getProgramPaths().push_back(GCCParentPath + "/../bin");
+        getFilePaths().push_back(LibcRoot + std::string("/lib/") + SubPath);
+        getFilePaths().push_back(GCCRoot + std::string("/") + SubPath);
+
+        LinkStdlib = true;
       }
     }
+
+    if (!LinkStdlib)
+      D.Diag(diag::warn_drv_avr_stdlib_not_linked);
+  }
 }
 
 void AVRToolChain::AddClangSystemIncludeArgs(const ArgList &DriverArgs,
@@ -415,14 +445,13 @@ void AVRToolChain::addClangTargetOptions(
 }
 
 Tool *AVRToolChain::buildLinker() const {
-  return new tools::AVR::Linker(getTriple(), *this);
+  return new tools::AVR::Linker(getTriple(), *this, LinkStdlib);
 }
 
 void AVR::Linker::ConstructJob(Compilation &C, const JobAction &JA,
                                const InputInfo &Output,
                                const InputInfoList &Inputs, const ArgList &Args,
                                const char *LinkingOutput) const {
-  const auto &TC = static_cast<const AVRToolChain &>(getToolChain());
   const Driver &D = getToolChain().getDriver();
 
   // Compute information about the target AVR.
@@ -444,39 +473,6 @@ void AVR::Linker::ConstructJob(Compilation &C, const JobAction &JA,
   Args.AddAllArgs(CmdArgs, options::OPT_L);
   getToolChain().AddFilePathLibArgs(Args, CmdArgs);
 
-  // Only add default libraries if the user hasn't explicitly opted out.
-  bool LinkStdlib = false;
-  if (!Args.hasArg(options::OPT_nostdlib) &&
-      !Args.hasArg(options::OPT_nodefaultlibs)) {
-    if (CPU.empty()) {
-      // We cannot link any standard libraries without an MCU specified.
-      D.Diag(diag::warn_drv_avr_mcu_not_specified);
-    } else {
-      Optional<StringRef> FamilyName = GetMCUFamilyName(CPU);
-      Optional<std::string> AVRLibcRoot = TC.findAVRLibcInstallation();
-
-      if (!FamilyName) {
-        // We do not have an entry for this CPU in the family
-        // mapping table yet.
-        D.Diag(diag::warn_drv_avr_family_linking_stdlibs_not_implemented)
-            << CPU;
-      } else if (!AVRLibcRoot) {
-        // No avr-libc found and so no runtime linked.
-        D.Diag(diag::warn_drv_avr_libc_not_found);
-      } else if (!TC.getGCCInstallPath().empty()) {
-        std::string SubPath = GetMCUSubPath(CPU);
-        CmdArgs.push_back(
-            Args.MakeArgString(Twine("-L") + *AVRLibcRoot + "/lib/" + SubPath));
-        CmdArgs.push_back(
-            Args.MakeArgString("-L" + TC.getGCCInstallPath() + "/" + SubPath));
-        LinkStdlib = true;
-      }
-    }
-
-    if (!LinkStdlib)
-      D.Diag(diag::warn_drv_avr_stdlib_not_linked);
-  }
-
   if (SectionAddressData.hasValue()) {
     std::string DataSectionArg = std::string("-Tdata=0x") +
                                  llvm::utohexstr(SectionAddressData.getValue());

clang/lib/Driver/ToolChains/AVR.h

@@ -31,14 +31,17 @@ public:
                         llvm::opt::ArgStringList &CC1Args,
                         Action::OffloadKind DeviceOffloadKind) const override;
 
-  llvm::Optional<std::string> findAVRLibcInstallation() const;
-  StringRef getGCCInstallPath() const { return GCCInstallPath; }
-
 protected:
   Tool *buildLinker() const override;
 
 private:
-  StringRef GCCInstallPath;
+  /// Whether libgcc, libct, and friends should be linked.
+  ///
+  /// This is not done if the user does not specify a
+  /// microcontroller on the command line.
+  bool LinkStdlib;
+
+  llvm::Optional<std::string> findAVRLibcInstallation() const;
 };
 
 } // end namespace toolchains
@@ -47,8 +50,9 @@ namespace tools {
 namespace AVR {
 class LLVM_LIBRARY_VISIBILITY Linker : public Tool {
 public:
-  Linker(const llvm::Triple &Triple, const ToolChain &TC)
+  Linker(const llvm::Triple &Triple, const ToolChain &TC, bool LinkStdlib)
-      : Tool("AVR::Linker", "avr-ld", TC), Triple(Triple) {}
+      : Tool("AVR::Linker", "avr-ld", TC), Triple(Triple),
+        LinkStdlib(LinkStdlib) {}
 
   bool hasIntegratedCPP() const override { return false; }
   bool isLinkJob() const override { return true; }
@@ -59,6 +63,7 @@ public:
 
 protected:
   const llvm::Triple &Triple;
+  bool LinkStdlib;
 };
 } // end namespace AVR
 } // end namespace tools

clang/test/Driver/avr-link-no-mcu-specified.c

@@ -0,0 +1,10 @@
+// RUN: %clang -### -target avr -no-canonical-prefixes -save-temps %s 2>&1 | FileCheck --check-prefix=WARN %s
+// RUN: %clang -### -target avr -no-canonical-prefixes -save-temps -mmcu=atmega328 %s 2>&1 | FileCheck --check-prefix=NOWARN %s
+
+// WARN: warning: no target microcontroller specified on command line, cannot link standard libraries, please pass -mmcu=<mcu name>
+// WARN: warning: standard library not linked and so no interrupt vector table or compiler runtime routines will be linked
+
+// NOWARN: main
+
+int main() { return 0; }
+

clang/test/Driver/avr-toolchain.c

@@ -35,11 +35,3 @@
 // RUN: %clang %s -### -target avr --sysroot %S/Inputs/basic_avr_tree 2>&1 -nostdinc | FileCheck --check-prefix=NOSTDINC %s
 // RUN: %clang %s -### -target avr --sysroot %S/Inputs/basic_avr_tree 2>&1 -nostdlibinc | FileCheck --check-prefix=NOSTDINC %s
 // NOSTDINC-NOT: "-internal-isystem" {{".*avr/include"}}
-
-// RUN: %clang -### --target=avr %s 2>&1 | FileCheck --check-prefix=WARN_STDLIB %s
-// RUN: %clang -### --target=avr -mmcu=atmega328 %s 2>&1 | FileCheck --check-prefix=NOWARN_STDLIB %s
-// RUN: %clang -### --target=avr -c %s 2>&1 | FileCheck --check-prefix=NOWARN_STDLIB %s
-
-// WARN_STDLIB: warning: no target microcontroller specified on command line, cannot link standard libraries, please pass -mmcu=<mcu name>
-// WARN_STDLIB: warning: standard library not linked and so no interrupt vector table or compiler runtime routines will be linked
-// NOWARN_STDLIB-NOT: warning: