Author: jmolenda
Date: Fri Dec 11 21:06:10 2015
New Revision: 255421
URL: http://llvm.org/viewvc/llvm-project?rev=255421&view=rev
Log:
Fix the L1 cache search in MemoryCache::Read to use the
stl upper_bound method instead of lower_bound - we were
failing to find some cached data in the L1 cache resulting
in extra memory read packets while stepping.
The bug with the existing code looked like this:
If the L1 cache has 8 bytes at address 0x1000 and 8 bytes
at address 0x2000 and we are searching for 4 bytes at 0x2004,
the use of lower_bound would return the end() of the container
and so we would incorrectly treat the memory as uncached.
(the L1 cache is memory seeded from debugserver in the T aka
questionmark packet, where debugserver will send up the stack
memory that likely contains the caller's stack pointer and
frame pointer values.)
<rdar://problem/23869227>
Modified:
lldb/trunk/source/Target/Memory.cpp
Modified: lldb/trunk/source/Target/Memory.cpp
URL:
http://llvm.org/viewvc/llvm-project/lldb/trunk/source/Target/Memory.cpp?rev=255421&r1=255420&r2=255421&view=diff
==============================================================================
--- lldb/trunk/source/Target/Memory.cpp (original)
+++ lldb/trunk/source/Target/Memory.cpp Fri Dec 11 21:06:10 2015
@@ -164,24 +164,16 @@ MemoryCache::Read (addr_t addr,
if (!m_L1_cache.empty())
{
AddrRange read_range(addr, dst_len);
- BlockMap::iterator pos = m_L1_cache.lower_bound(addr);
- if (pos != m_L1_cache.end())
+ BlockMap::iterator pos = m_L1_cache.upper_bound(addr);
+ if (pos != m_L1_cache.begin ())
{
- AddrRange chunk_range(pos->first, pos->second->GetByteSize());
- bool match = chunk_range.Contains(read_range);
- if (!match && pos != m_L1_cache.begin())
- {
- --pos;
- chunk_range.SetRangeBase(pos->first);
- chunk_range.SetByteSize(pos->second->GetByteSize());
- match = chunk_range.Contains(read_range);
- }
-
- if (match)
- {
- memcpy(dst, pos->second->GetBytes() + addr -
chunk_range.GetRangeBase(), dst_len);
- return dst_len;
- }
+ --pos;
+ }
+ AddrRange chunk_range(pos->first, pos->second->GetByteSize());
+ if (chunk_range.Contains(read_range))
+ {
+ memcpy(dst, pos->second->GetBytes() + addr -
chunk_range.GetRangeBase(), dst_len);
+ return dst_len;
}
}
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