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

[Zhigang Gong]

On Tue, Jul 16, 2013 at 11:19:55AM +0800, He Junyan wrote:
> On 07/16/2013 10:54 AM, Zhigang Gong wrote:
> >This patch really accelerate the compiling speed dramaticlly. Thanks.
> >
> >One comment as below:
> >
> >On Mon, Jul 15, 2013 at 06:22:37PM +0800, junyan.he at inbox.com wrote:
> >>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.
> >I think this is not convenient for developers and may bring some
> >confusing. I have two ideas to mitigate or solve this problem:
> >
> >1. precompile the header file at the gbe's build time. Then we will get an up-to-date
> >pch file embedded in the gbe library.
> Do you mean generate the pch file when make ?
Exactly. 

> >
> >2. compute a hash value of the ocl_header.h at gbe's build time, and store this hash
> >value into the pch file (not very sure whether pch file format can contain any comments
> >like data, but at least we still can save this hash value to ocl_header.h.hash file at
> >the same location of the ocl_header.h.pch). At the gbe runtime, we just need to compare
> >current hash value with the one in the pch file to determine whether we need to update
> >a new pch file.
> >
> >The first solution is the ideal solution. And the second is also not too bad, as
> >we only compute the hash value at gbe's build time and it doesn't bring any overhead
> >to the application for the hash value computing.
> >
> >Any thoughts?
> >
> >>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
> >>
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> 
>