[PATCH] D20454: Eliminate unnecessary file access checks in Clang driver on Windows

Adrian McCarthy via cfe-commits cfe-commits at lists.llvm.org
Thu May 19 15:57:31 PDT 2016

amccarth created this revision.
amccarth added a reviewer: majnemer.
amccarth added a subscriber: cfe-commits.

This fixes the problem where the driver will look for cl.exe.exe while walking the PATH.

I looked into changing the Windows implementation of llvm::sys::fs::can_execute(), but there wasn't a satisfying way to preserve the extra checks for the callers that depend on it.  I also looked into having it actually check that the file is an executable, but this seemed to add little value at the cost of more file i/o.



Index: lib/Driver/MSVCToolChain.cpp
--- lib/Driver/MSVCToolChain.cpp
+++ lib/Driver/MSVCToolChain.cpp
@@ -408,7 +408,10 @@
         SmallString<128> FilePath(PathSegment);
         llvm::sys::path::append(FilePath, "cl.exe");
-        if (llvm::sys::fs::can_execute(FilePath.c_str()) &&
+        // Checking if cl.exe exists is a small optimization over calling
+        // can_execute, which really only checks for existence but will also do
+        // extra checks for cl.exe.exe.  These add up when walking a long path.
+        if (llvm::sys::fs::exists(FilePath.c_str()) &&
             !llvm::sys::fs::equivalent(FilePath.c_str(), clangProgramPath)) {
           // If we found it on the PATH, use it exactly as is with no
           // modifications.

-------------- next part --------------
A non-text attachment was scrubbed...
Name: D20454.57872.patch
Type: text/x-patch
Size: 829 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/cfe-commits/attachments/20160519/c9d93161/attachment.bin>

More information about the cfe-commits mailing list