[Beignet] [PATCH] Add the PCH support when building the source.

[junyan.he at inbox.com]

From: Junyan He <junyan.he at linux.intel.com>

Because the utest grows bigger, the runtime compiling time
seems a big problem to cause the utest_run very slow.
Most of the time wastes on re-parsing the big header file
such as ocl_stdlib.h.
Using the PCH feature of Clang can shorten the compiling time
a lot.
One shortcut: the PCH file in the /tmp/ will not be updated
automaticly when you modify the ocl_stdlib.h. You should remove
the pch file manually.

Signed-off-by: Junyan He <junyan.he at linux.intel.com>
---
 backend/src/backend/program.cpp |   54 +++++++++++++++++++++++++++++++++++----
 1 file changed, 49 insertions(+), 5 deletions(-)

diff --git a/backend/src/backend/program.cpp b/backend/src/backend/program.cpp
index 2a4feb9..8f1cf61 100644
--- a/backend/src/backend/program.cpp
+++ b/backend/src/backend/program.cpp
@@ -229,18 +229,62 @@ namespace gbe {
                                           size_t *errSize)
   {
     char clStr[L_tmpnam+1], llStr[L_tmpnam+1];
+    std::string clOpt;
+    const std::string header = "/tmp/ocl_header.h";
+    const std::string header_pch = "/tmp/ocl_header.h.pch";
     const std::string clName = std::string(tmpnam_r(clStr)) + ".cl"; /* unsafe! */
     const std::string llName = std::string(tmpnam_r(llStr)) + ".ll"; /* unsafe! */
-
-    // Write the source to the cl file
+    FILE *clHeader = NULL;
     FILE *clFile = fopen(clName.c_str(), "w");
     FATAL_IF(clFile == NULL, "Failed to open temporary file");
-    fwrite(ocl_common_defines_str.c_str(), strlen(ocl_common_defines_str.c_str()), 1, clFile);
-    fwrite(ocl_stdlib_str.c_str(), strlen(ocl_stdlib_str.c_str()), 1, clFile);
+
+    /* Use the header_pch to save the tokenized file. */
+    if (::access(header_pch.c_str(), R_OK)) {
+      std::string cmd;
+      clHeader = fopen(header.c_str(), "w");
+      FATAL_IF(clHeader == NULL, "Failed to open header file");
+
+      fwrite(ocl_common_defines_str.c_str(), strlen(ocl_common_defines_str.c_str()), 1, clHeader);
+      fwrite(ocl_stdlib_str.c_str(), strlen(ocl_stdlib_str.c_str()), 1, clHeader);
+      fclose(clHeader);
+
+      cmd += "clang -cc1 ";
+      cmd += "-emit-pch ";
+      cmd += header;
+      cmd += " ";
+      cmd += "-x ";
+      cmd +=" cl ";
+
+#if LLVM_VERSION_MINOR <= 2
+      cmd +="-triple ";
+      cmd +="nvptx ";
+#else
+      cmd +="-triple ";
+      cmd +="spir ";
+#endif /* LLVM_VERSION_MINOR <= 2 */
+
+#if LLVM_VERSION_MINOR <= 1
+      cmd +="-triple ";
+      cmd +="ptx32 ";
+#else
+      cmd += "-ffp-contract=off ";
+#endif /* LLVM_VERSION_MINOR <= 1 */
+      cmd += "-o ";
+      cmd += header_pch;
+      ::system(cmd.c_str());
+    }
+
+    // Write the source to the cl file
     fwrite(source, strlen(source), 1, clFile);
     fclose(clFile);
 
-    buildModuleFromSource(clName.c_str(), llName.c_str(), options ? options : "");
+    clOpt += "-include-pch";
+    clOpt += " ";
+    clOpt += header_pch;
+    clOpt += " ";
+    if(options)
+      clOpt += options;
+    buildModuleFromSource(clName.c_str(), llName.c_str(), clOpt.c_str());
     remove(clName.c_str());
 
     // Now build the program from llvm
-- 
1.7.9.5