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commit 227da84c3757eb857008e7b82aad622ed959eb84
Author: Joe McDonnell <joemcdonn...@cloudera.com>
AuthorDate: Wed May 27 16:21:36 2020 -0700
IMPALA-9781: Fix GCC 7 unaligned 128-bit loads / stores
When running a release binary built with GCC 7.5.0, it crashes
with an unaligned memory error in multiple pieces of code.
In these locations, we are doing stores to 128-bit values, but we
cannot guarantee alignment. GCC 7 must be optimizing the code to
use instructions that require a higher level of alignment than
we can provide.
This switches the code locations to use memset / memcpy with
local variables to avoid the unaligned stores.
Testing:
- Ran exhaustive tests with a release binary built by GCC 7.5.0
- Ran exhaustive tests
Change-Id: I67320790789d5b57aeaf2dff0eae7352a1cbf81e
Reviewed-on: http://gerrit.cloudera.org:8080/15993
Reviewed-by: Impala Public Jenkins <impala-public-jenk...@cloudera.com>
Tested-by: Impala Public Jenkins <impala-public-jenk...@cloudera.com>
---
be/src/exprs/slot-ref.cc | 5 ++++-
be/src/util/decimal-util.h | 3 ++-
be/src/util/dict-encoding.h | 5 +++--
3 files changed, 9 insertions(+), 4 deletions(-)
diff --git a/be/src/exprs/slot-ref.cc b/be/src/exprs/slot-ref.cc
index 634a989..661c7ef 100644
--- a/be/src/exprs/slot-ref.cc
+++ b/be/src/exprs/slot-ref.cc
@@ -422,7 +422,10 @@ DecimalVal SlotRef::GetDecimalValInterpreted(
case 8:
return DecimalVal(*reinterpret_cast<int64_t*>(t->GetSlot(slot_offset_)));
case 16:
- return
DecimalVal(*reinterpret_cast<int128_t*>(t->GetSlot(slot_offset_)));
+ // Avoid an unaligned load by using memcpy
+ __int128_t val;
+ memcpy(&val, t->GetSlot(slot_offset_), sizeof(val));
+ return DecimalVal(val);
default:
DCHECK(false);
return DecimalVal::null();
diff --git a/be/src/util/decimal-util.h b/be/src/util/decimal-util.h
index f505ecc..4ddfe23 100644
--- a/be/src/util/decimal-util.h
+++ b/be/src/util/decimal-util.h
@@ -128,7 +128,8 @@ class DecimalUtil {
const uint8_t* buffer, int fixed_len_size, T* v) {
DCHECK_GT(fixed_len_size, 0);
DCHECK_LE(fixed_len_size, sizeof(T));
- *v = 0;
+ // Avoid an unaligned store by using memset
+ memset(v, 0, sizeof(T));
// We need to sign extend val. For example, if the original value was
// -1, the original bytes were -1,-1,-1,-1. If we only wrote out 1 byte,
after
// the encode step above, val would contain (-1, 0, 0, 0). We need to sign
diff --git a/be/src/util/dict-encoding.h b/be/src/util/dict-encoding.h
index f440332..e6e01bc 100644
--- a/be/src/util/dict-encoding.h
+++ b/be/src/util/dict-encoding.h
@@ -346,10 +346,11 @@ class DictDecoder : public DictDecoderBase {
virtual int num_entries() const { return dict_.size(); }
virtual void GetValue(int index, void* buffer) {
- T* val_ptr = reinterpret_cast<T*>(buffer);
DCHECK_GE(index, 0);
DCHECK_LT(index, dict_.size());
- *val_ptr = dict_[index];
+ // Avoid an unaligned store by using memcpy
+ T val = dict_[index];
+ memcpy(buffer, reinterpret_cast<const void*>(&val), sizeof(T));
}
/// Returns the next value. Returns false if the data is invalid.
