[ThinLTO] Update ThinLTO cache file atimes when on Windows

ThinLTO cache file access times are used for expiration based pruning
and since Vista, file access times are not updated by Windows by
default:

https://blogs.technet.microsoft.com/filecab/2006/11/07/disabling-last-access-time-in-windows-vista-to-improve-ntfs-performance

This means on Windows, cache files are currently being pruned from
creation time. This change manually updates cache files that are
accessed by ThinLTO, when on Windows.

Patch by Owen Reynolds.

Differential Revision: https://reviews.llvm.org/D47266

llvm-svn: 336276

1 files changed, 15 insertions, 0 deletions

diff --git a/llvm/lib/Support/Windows/Path.inc b/llvm/lib/Support/Windows/Path.inc
index 577d57199d5..f425d607af4 100644
--- a/llvm/lib/Support/Windows/Path.inc
+++ b/llvm/lib/Support/Windows/Path.inc
@@ -1049,6 +1049,8 @@ static DWORD nativeAccess(FileAccess Access, OpenFlags Flags) {
     Result |= GENERIC_WRITE;
   if (Flags & OF_Delete)
     Result |= DELETE;
+  if (Flags & OF_UpdateAtime)
+    Result |= FILE_WRITE_ATTRIBUTES;
   return Result;
 }
 
@@ -1104,6 +1106,19 @@ Expected<file_t> openNativeFile(const Twine &Name, CreationDisposition Disp,
       Name, Result, NativeDisp, NativeAccess, FILE_ATTRIBUTE_NORMAL, Inherit);
   if (EC)
     return errorCodeToError(EC);
+
+  if (Flags & OF_UpdateAtime) {
+    FILETIME FileTime;
+    SYSTEMTIME SystemTime;
+    GetSystemTime(&SystemTime);
+    if (SystemTimeToFileTime(&SystemTime, &FileTime) == 0 ||
+        SetFileTime(Result, NULL, &FileTime, NULL) == 0) {
+      DWORD LastError = ::GetLastError();
+      ::CloseHandle(Result);
+      return errorCodeToError(mapWindowsError(LastError));
+    }
+  }
+
   if (Flags & OF_Delete) {
     if ((EC = setDeleteDisposition(Result, true))) {
       ::CloseHandle(Result);