CUDA: Clang separable compilation

For NVCC the compiler takes care of device linking when passed the "-dlink"
flag.
Clang doesn't support such magic and requires the buildsystem to do the work
that NVCC does behind the scenes.

The implementation is based on Bazel's device linking documentation:
https://github.com/tensorflow/tensorflow/blob/7cabcdf073abad8c46e9dda62bb8fa4682d2061e/third_party/nccl/build_defs.bzl.tpl#L259

Closes: #20726

1 files changed, 41 insertions, 32 deletions

diff --git a/Source/cmMakefileLibraryTargetGenerator.cxx b/Source/cmMakefileLibraryTargetGenerator.cxx
index 1c25fc4..b32ea6a 100644
--- a/Source/cmMakefileLibraryTargetGenerator.cxx
+++ b/Source/cmMakefileLibraryTargetGenerator.cxx
@@ -129,8 +129,7 @@ void cmMakefileLibraryTargetGenerator::WriteStaticLibraryRules()
   const bool requiresDeviceLinking = requireDeviceLinking(
     *this->GeneratorTarget, *this->LocalGenerator, this->GetConfigName());
   if (requiresDeviceLinking) {
-    std::string linkRuleVar = "CMAKE_CUDA_DEVICE_LINK_LIBRARY";
-    this->WriteDeviceLibraryRules(linkRuleVar, false);
+    this->WriteDeviceLibraryRules("CMAKE_CUDA_DEVICE_LINK_LIBRARY", false);
   }
 
   std::string linkLanguage =
@@ -156,8 +155,7 @@ void cmMakefileLibraryTargetGenerator::WriteSharedLibraryRules(bool relink)
     const bool requiresDeviceLinking = requireDeviceLinking(
       *this->GeneratorTarget, *this->LocalGenerator, this->GetConfigName());
     if (requiresDeviceLinking) {
-      std::string linkRuleVar = "CMAKE_CUDA_DEVICE_LINK_LIBRARY";
-      this->WriteDeviceLibraryRules(linkRuleVar, relink);
+      this->WriteDeviceLibraryRules("CMAKE_CUDA_DEVICE_LINK_LIBRARY", relink);
     }
   }
 
@@ -191,8 +189,7 @@ void cmMakefileLibraryTargetGenerator::WriteModuleLibraryRules(bool relink)
     const bool requiresDeviceLinking = requireDeviceLinking(
       *this->GeneratorTarget, *this->LocalGenerator, this->GetConfigName());
     if (requiresDeviceLinking) {
-      std::string linkRuleVar = "CMAKE_CUDA_DEVICE_LINK_LIBRARY";
-      this->WriteDeviceLibraryRules(linkRuleVar, relink);
+      this->WriteDeviceLibraryRules("CMAKE_CUDA_DEVICE_LINK_LIBRARY", relink);
     }
   }
 
@@ -239,29 +236,13 @@ void cmMakefileLibraryTargetGenerator::WriteDeviceLibraryRules(
   // TODO: Merge the methods that call this method to avoid
   // code duplication.
   std::vector<std::string> commands;
-
-  // Get the language to use for linking this library.
-  std::string linkLanguage = "CUDA";
   std::string const objExt =
     this->Makefile->GetSafeDefinition("CMAKE_CUDA_OUTPUT_EXTENSION");
 
-  // Build list of dependencies.
-  std::vector<std::string> depends;
-  this->AppendLinkDepends(depends, linkLanguage);
-
-  // Add language-specific flags.
-  std::string langFlags;
-  this->LocalGenerator->AddLanguageFlagsForLinking(
-    langFlags, this->GeneratorTarget, linkLanguage, this->GetConfigName());
-
-  // Create set of linking flags.
-  std::string linkFlags;
-  this->GetDeviceLinkFlags(linkFlags, linkLanguage);
-
   // Get the name of the device object to generate.
-  std::string const targetOutputReal =
+  std::string const targetOutput =
     this->GeneratorTarget->ObjectDirectory + "cmake_device_link" + objExt;
-  this->DeviceLinkObject = targetOutputReal;
+  this->DeviceLinkObject = targetOutput;
 
   this->NumberOfProgressActions++;
   if (!this->NoRuleMessages) {
@@ -269,7 +250,7 @@ void cmMakefileLibraryTargetGenerator::WriteDeviceLibraryRules(
     this->MakeEchoProgress(progress);
     // Add the link message.
     std::string buildEcho =
-      cmStrCat("Linking ", linkLanguage, " device code ",
+      cmStrCat("Linking CUDA device code ",
                this->LocalGenerator->ConvertToOutputFormat(
                  this->LocalGenerator->MaybeConvertToRelativePath(
                    this->LocalGenerator->GetCurrentBinaryDirectory(),
@@ -278,10 +259,41 @@ void cmMakefileLibraryTargetGenerator::WriteDeviceLibraryRules(
     this->LocalGenerator->AppendEcho(
       commands, buildEcho, cmLocalUnixMakefileGenerator3::EchoLink, &progress);
   }
+
+  if (this->Makefile->GetSafeDefinition("CMAKE_CUDA_COMPILER_ID") == "Clang") {
+    this->WriteDeviceLinkRule(commands, targetOutput);
+  } else {
+    this->WriteNvidiaDeviceLibraryRules(linkRuleVar, relink, commands,
+                                        targetOutput);
+  }
+
+  // Write the main driver rule to build everything in this target.
+  this->WriteTargetDriverRule(targetOutput, relink);
+}
+
+void cmMakefileLibraryTargetGenerator::WriteNvidiaDeviceLibraryRules(
+  const std::string& linkRuleVar, bool relink,
+  std::vector<std::string>& commands, const std::string& targetOutput)
+{
+  std::string linkLanguage = "CUDA";
+
+  // Build list of dependencies.
+  std::vector<std::string> depends;
+  this->AppendLinkDepends(depends, linkLanguage);
+
+  // Add language-specific flags.
+  std::string langFlags;
+  this->LocalGenerator->AddLanguageFlagsForLinking(
+    langFlags, this->GeneratorTarget, linkLanguage, this->GetConfigName());
+
+  // Create set of linking flags.
+  std::string linkFlags;
+  this->GetDeviceLinkFlags(linkFlags, linkLanguage);
+
   // Clean files associated with this library.
   std::set<std::string> libCleanFiles;
   libCleanFiles.insert(this->LocalGenerator->MaybeConvertToRelativePath(
-    this->LocalGenerator->GetCurrentBinaryDirectory(), targetOutputReal));
+    this->LocalGenerator->GetCurrentBinaryDirectory(), targetOutput));
 
   // Determine whether a link script will be used.
   bool useLinkScript = this->GlobalGenerator->GetUseLinkScript();
@@ -335,7 +347,7 @@ void cmMakefileLibraryTargetGenerator::WriteDeviceLibraryRules(
 
     std::string target = this->LocalGenerator->ConvertToOutputFormat(
       this->LocalGenerator->MaybeConvertToRelativePath(
-        this->LocalGenerator->GetCurrentBinaryDirectory(), targetOutputReal),
+        this->LocalGenerator->GetCurrentBinaryDirectory(), targetOutput),
       output);
 
     std::string targetFullPathCompilePDB =
@@ -364,7 +376,7 @@ void cmMakefileLibraryTargetGenerator::WriteDeviceLibraryRules(
       this->LocalGenerator->CreateRulePlaceholderExpander());
 
     // Construct the main link rule and expand placeholders.
-    rulePlaceholderExpander->SetTargetImpLib(targetOutputReal);
+    rulePlaceholderExpander->SetTargetImpLib(targetOutput);
     std::string linkRule = this->GetLinkRule(linkRuleVar);
     cmExpandList(linkRule, real_link_commands);
 
@@ -399,14 +411,11 @@ void cmMakefileLibraryTargetGenerator::WriteDeviceLibraryRules(
   commands1.clear();
 
   // Compute the list of outputs.
-  std::vector<std::string> outputs(1, targetOutputReal);
+  std::vector<std::string> outputs(1, targetOutput);
 
   // Write the build rule.
   this->WriteMakeRule(*this->BuildFileStream, nullptr, outputs, depends,
                       commands, false);
-
-  // Write the main driver rule to build everything in this target.
-  this->WriteTargetDriverRule(targetOutputReal, relink);
 #else
   static_cast<void>(linkRuleVar);
   static_cast<void>(relink);