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> llvm-svn: 255421
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@ -164,24 +164,16 @@ MemoryCache::Read (addr_t addr,
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if (!m_L1_cache.empty())
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{
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AddrRange read_range(addr, dst_len);
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BlockMap::iterator pos = m_L1_cache.lower_bound(addr);
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if (pos != m_L1_cache.end())
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BlockMap::iterator pos = m_L1_cache.upper_bound(addr);
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if (pos != m_L1_cache.begin ())
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{
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AddrRange chunk_range(pos->first, pos->second->GetByteSize());
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bool match = chunk_range.Contains(read_range);
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if (!match && pos != m_L1_cache.begin())
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{
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--pos;
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chunk_range.SetRangeBase(pos->first);
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chunk_range.SetByteSize(pos->second->GetByteSize());
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match = chunk_range.Contains(read_range);
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}
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if (match)
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{
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memcpy(dst, pos->second->GetBytes() + addr - chunk_range.GetRangeBase(), dst_len);
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return dst_len;
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}
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--pos;
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}
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AddrRange chunk_range(pos->first, pos->second->GetByteSize());
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if (chunk_range.Contains(read_range))
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{
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memcpy(dst, pos->second->GetBytes() + addr - chunk_range.GetRangeBase(), dst_len);
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return dst_len;
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}
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}
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