Propagate backtraces from LINK_LIBRARIES through to link line items

Since commit d4d0dd0f6a (cmLinkLineComputer: Add ComputeLinkLibs
overload with backtraces, 2019-09-13, v3.16.0-rc1~87^2~4), backtraces
have been collected by `ComputeLinkLibs` by looking back through the
link implementation libraries for one matching the text of the link line
item.  This is slow in projects with long link lines.

Instead, teach `cmComputeLinkDepends` and `cmComputeLinkInformation` to
carry backtrace information explicitly along with the text of each item.

Fixes: #20322

1 files changed, 11 insertions, 9 deletions

diff --git a/Source/cmComputeLinkInformation.h b/Source/cmComputeLinkInformation.h
index 92ab83b..ee74ccd 100644
--- a/Source/cmComputeLinkInformation.h
+++ b/Source/cmComputeLinkInformation.h
@@ -13,13 +13,13 @@
 
 #include "cmsys/RegularExpression.hxx"
 
+#include "cmListFileCache.h"
+
 class cmGeneratorTarget;
 class cmGlobalGenerator;
 class cmMakefile;
 class cmOrderDirectories;
 class cmake;
-template <typename T>
-class BT;
 
 /** \class cmComputeLinkInformation
  * \brief Compute link information for a target in one configuration.
@@ -35,13 +35,13 @@ public:
   struct Item
   {
     Item() = default;
-    Item(std::string v, bool p, cmGeneratorTarget const* target = nullptr)
+    Item(BT<std::string> v, bool p, cmGeneratorTarget const* target = nullptr)
       : Value(std::move(v))
       , IsPath(p)
       , Target(target)
     {
     }
-    std::string Value;
+    BT<std::string> Value;
     bool IsPath = true;
     cmGeneratorTarget const* Target = nullptr;
   };
@@ -74,8 +74,9 @@ public:
   const cmGeneratorTarget* GetTarget() { return this->Target; }
 
 private:
-  void AddItem(std::string const& item, const cmGeneratorTarget* tgt);
-  void AddSharedDepItem(std::string const& item, cmGeneratorTarget const* tgt);
+  void AddItem(BT<std::string> const& item, const cmGeneratorTarget* tgt);
+  void AddSharedDepItem(BT<std::string> const& item,
+                        cmGeneratorTarget const* tgt);
 
   // Output information.
   ItemVector Items;
@@ -146,10 +147,11 @@ private:
   std::string NoCaseExpression(const char* str);
 
   // Handling of link items.
-  void AddTargetItem(std::string const& item, const cmGeneratorTarget* target);
-  void AddFullItem(std::string const& item);
+  void AddTargetItem(BT<std::string> const& item,
+                     const cmGeneratorTarget* target);
+  void AddFullItem(BT<std::string> const& item);
   bool CheckImplicitDirItem(std::string const& item);
-  void AddUserItem(std::string const& item, bool pathNotKnown);
+  void AddUserItem(BT<std::string> const& item, bool pathNotKnown);
   void AddDirectoryItem(std::string const& item);
   void AddFrameworkItem(std::string const& item);
   void DropDirectoryItem(std::string const& item);