cmDepends: merge dependers of depend makefile

Since one depender has multiple dependees, depend makefile generated
same depender line by line, to reduce file size and refine make file
parse speed, merge same dependers to one. And add a testcase for
large depend.make which generated source file includes 20000 header
files and run build and incremental build

Signed-off-by: Wangkai <wangkai86@huawei.com>
Signed-off-by: Zhaoyingdong <zhaoyingdong@huawei.com>

1 files changed, 14 insertions, 5 deletions

diff --git a/Source/cmDependsCompiler.cxx b/Source/cmDependsCompiler.cxx
index beb080ffb3..97534bcdb7 100644
--- a/Source/cmDependsCompiler.cxx
+++ b/Source/cmDependsCompiler.cxx
@@ -196,6 +196,9 @@ void cmDependsCompiler::WriteDependencies(
   const auto& lineContinue = static_cast<cmGlobalUnixMakefileGenerator3*>(
                                this->LocalGenerator->GetGlobalGenerator())
                                ->LineContinueDirective;
+  bool supportLongLineDepend = static_cast<cmGlobalUnixMakefileGenerator3*>(
+                                 this->LocalGenerator->GetGlobalGenerator())
+                                 ->SupportsLongLineDependencies();
   const auto& binDir = this->LocalGenerator->GetBinaryDirectory();
   cmDepends::DependencyMap makeDependencies(dependencies);
   std::unordered_set<cm::string_view> phonyTargets;
@@ -213,13 +216,19 @@ void cmDependsCompiler::WriteDependencies(
       });
 
     bool first_dep = true;
-    makeDepends << target << ": ";
+    if (supportLongLineDepend) {
+      makeDepends << target << ": ";
+    }
     for (const auto& dep : deps) {
-      if (first_dep) {
-        first_dep = false;
-        makeDepends << dep;
+      if (supportLongLineDepend) {
+        if (first_dep) {
+          first_dep = false;
+          makeDepends << dep;
+        } else {
+          makeDepends << ' ' << lineContinue << "  " << dep;
+        }
       } else {
-        makeDepends << ' ' << lineContinue << "  " << dep;
+        makeDepends << target << ": " << dep << std::endl;
       }
 
       phonyTargets.emplace(dep.data(), dep.length());