From 499befab3136ec5c3a2e984d46ace5afe15c1f7b Mon Sep 17 00:00:00 2001
From: NAKAMURA Takumi <geek4civic@gmail.com>
Date: Mon, 4 Aug 2014 01:43:37 +0000
Subject: [PATCH] MemoryBuffer: Don't use mmap when FileSize is multiple of 4k
 on Cygwin.

On Cygwin, getpagesize() returns 64k(AllocationGranularity).

In r214580, the size of X86GenInstrInfo.inc became 1499136.

FIXME: We should reorganize again getPageSize() on Win32.
MapFile allocates address along AllocationGranularity but view is mapped by physical page.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@214681 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Support/MemoryBuffer.cpp | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/lib/Support/MemoryBuffer.cpp b/lib/Support/MemoryBuffer.cpp
index 5f4b7daae53..522c365f3d5 100644
--- a/lib/Support/MemoryBuffer.cpp
+++ b/lib/Support/MemoryBuffer.cpp
@@ -305,6 +305,14 @@ static bool shouldUseMmap(int FD,
   if ((FileSize & (PageSize -1)) == 0)
     return false;
 
+#if defined(__CYGWIN__)
+  // Don't try to map files that are exactly a multiple of the physical page size
+  // if we need a null terminator.
+  // FIXME: We should reorganize again getPageSize() on Win32.
+  if ((FileSize & (4096 - 1)) == 0)
+    return false;
+#endif
+
   return true;
 }