Index: lldb/trunk/packages/Python/lldbsuite/test/functionalities/memory/cache/Makefile
===================================================================
--- lldb/trunk/packages/Python/lldbsuite/test/functionalities/memory/cache/Makefile
+++ lldb/trunk/packages/Python/lldbsuite/test/functionalities/memory/cache/Makefile
@@ -0,0 +1,5 @@
+LEVEL = ../../../make
+
+CXX_SOURCES := main.cpp
+
+include $(LEVEL)/Makefile.rules
Index: lldb/trunk/packages/Python/lldbsuite/test/functionalities/memory/cache/TestMemoryCache.py
===================================================================
--- lldb/trunk/packages/Python/lldbsuite/test/functionalities/memory/cache/TestMemoryCache.py
+++ lldb/trunk/packages/Python/lldbsuite/test/functionalities/memory/cache/TestMemoryCache.py
@@ -0,0 +1,62 @@
+"""
+Test the MemoryCache L1 flush.
+"""
+
+from __future__ import print_function
+
+
+
+import os, time
+import re
+import lldb
+from lldbsuite.test.lldbtest import *
+import lldbsuite.test.lldbutil as lldbutil
+
+class MemoryCacheTestCase(TestBase):
+
+    mydir = TestBase.compute_mydir(__file__)
+
+    def setUp(self):
+        # Call super's setUp().
+        TestBase.setUp(self)
+        # Find the line number to break inside main().
+        self.line = line_number('main.cpp', '// Set break point at this line.')
+
+    def test_memory_cache(self):
+        """Test the MemoryCache class with a sequence of 'memory read' and 'memory write' operations."""
+        self.build()
+        exe = os.path.join(os.getcwd(), "a.out")
+        self.runCmd("file " + exe, CURRENT_EXECUTABLE_SET)
+
+        # Break in main() after the variables are assigned values.
+        lldbutil.run_break_set_by_file_and_line (self, "main.cpp", self.line, num_expected_locations=1, loc_exact=True)
+
+        self.runCmd("run", RUN_SUCCEEDED)
+
+        # The stop reason of the thread should be breakpoint.
+        self.expect("thread list", STOPPED_DUE_TO_BREAKPOINT,
+            substrs = ['stopped', 'stop reason = breakpoint'])
+
+        # The breakpoint should have a hit count of 1.
+        self.expect("breakpoint list -f", BREAKPOINT_HIT_ONCE,
+            substrs = [' resolved, hit count = 1'])
+
+        # Read a chunk of memory containing &my_ints[0]. The number of bytes read
+        # must be greater than m_L2_cache_line_byte_size to make sure the L1
+        # cache is used.
+        self.runCmd('memory read -f d -c 201 `&my_ints - 100`')
+
+        # Check the value of my_ints[0] is the same as set in main.cpp.
+        line = self.res.GetOutput().splitlines()[100]
+        self.assertTrue(0x00000042 == int(line.split(':')[1], 0))
+
+        # Change the value of my_ints[0] in memory.
+        self.runCmd("memory write `&my_ints` AA")
+
+        # Re-read the chunk of memory. The cache line should have been
+        # flushed because of the 'memory write'.
+        self.runCmd('memory read -f d -c 201 `&my_ints - 100`')
+
+        # Check the value of my_ints[0] have been updated correctly.
+        line = self.res.GetOutput().splitlines()[100]
+        self.assertTrue(0x000000AA == int(line.split(':')[1], 0))
Index: lldb/trunk/packages/Python/lldbsuite/test/functionalities/memory/cache/main.cpp
===================================================================
--- lldb/trunk/packages/Python/lldbsuite/test/functionalities/memory/cache/main.cpp
+++ lldb/trunk/packages/Python/lldbsuite/test/functionalities/memory/cache/main.cpp
@@ -0,0 +1,14 @@
+//===-- main.cpp ------------------------------------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+int main ()
+{
+    int my_ints[] = {0x42};
+    return 0; // Set break point at this line.
+}
Index: lldb/trunk/source/Target/Memory.cpp
===================================================================
--- lldb/trunk/source/Target/Memory.cpp
+++ lldb/trunk/source/Target/Memory.cpp
@@ -78,7 +78,11 @@
     if (!m_L1_cache.empty())
     {
         AddrRange flush_range(addr, size);
-        BlockMap::iterator pos = m_L1_cache.lower_bound(addr);
+        BlockMap::iterator pos = m_L1_cache.upper_bound(addr);
+        if (pos != m_L1_cache.begin())
+        {
+            --pos;
+        }
         while (pos != m_L1_cache.end())
         {
             AddrRange chunk_range(pos->first, pos->second->GetByteSize());