improve pch

1 files changed, 22 insertions, 3 deletions

diff --git a/xmake/rules/c++/precompiled_header/xmake.lua b/xmake/rules/c++/precompiled_header/xmake.lua
index a2b08fe46..d67535cc6 100644
--- a/xmake/rules/c++/precompiled_header/xmake.lua
+++ b/xmake/rules/c++/precompiled_header/xmake.lua
@@ -22,19 +22,38 @@ rule("c.build.pcheader")
     on_config(function (target, opt)
         import("private.action.build.pcheader").config(target, "c", opt)
     end)
-    before_prepare(function (target, jobgraph, opt)
+
+    before_build(function (target, jobgraph, opt)
         if not os.getenv("XMAKE_IN_COMPILE_COMMANDS_PROJECT_GENERATOR") then
             import("private.action.build.pcheader").build(target, jobgraph, "c", opt)
         end
     end, {jobgraph = true})
 
 rule("c++.build.pcheader")
-    add_orders("c++.build.modules.scanner", "c++.build.pcheader", "c++.build.modules.builder")
     on_config(function (target, opt)
         import("private.action.build.pcheader").config(target, "cxx", opt)
     end)
+
+    -- If the current target has a C++ modules file,
+    -- we can only compile it earlier in the before_prepare stage,
+    -- because the C++ modules will perform a complete dependency scan of
+    -- the C++ files in on_prepare and then build the dependency graph.
+    -- At this time, the pch header file must have already been generated.
     before_prepare(function (target, jobgraph, opt)
-        if not os.getenv("XMAKE_IN_COMPILE_COMMANDS_PROJECT_GENERATOR") then
+        local has_modules = target:data("cxx.has_modules")
+        if has_modules and not os.getenv("XMAKE_IN_COMPILE_COMMANDS_PROJECT_GENERATOR") then
+            import("private.action.build.pcheader").build(target, jobgraph, "cxx", opt)
+        end
+    end, {jobgraph = true})
+
+    -- To enable parallel compilation across targets
+    -- without blocking the compilation of other cpp files,
+    -- we perform this as much as possible during the before_build stage.
+    --
+    -- @see: https://github.com/xmake-io/xmake/issues/4167
+    before_build(function (target, jobgraph, opt)
+        local has_modules = target:data("cxx.has_modules")
+        if not has_modules then
             import("private.action.build.pcheader").build(target, jobgraph, "cxx", opt)
         end
     end, {jobgraph = true})