Fixing various bugs all over the VM that make assumptions about RefData
and TypedValue layout. Here are the assumptions fixed by this diff:
offsetof(RefData, m_tv) == 0. Both JIT's assumed this in many subtle
ways, by punning RefData* as TypedValue* without adding an offset.
This assumption also causes RefData._count to overlap TypedValue.m_aux,
which constraints TypedValue layout.
offsetof(TypedValue, m_data) == 0. gen_ext_hhvm.php assumes you
can cast TypedValue* to Value*; the JITs often weren't using
offsetof(TypedValue, m_data) in their addressing calculations. HHIR
assumed return-by-value TV's have m_data/m_type in rax/rdx, which
can change when TV layout changes.
offsetof(TypedValue, m_type) > 8 is an assumption baked into the
pass-by-value register assignment logic in HHIR's codegen.cpp; if
the type is in the low word, register assignment is swapped.
sizeof(TypedValue::m_type) == 4. We used dword-sized operations
in both JIT's when accessing m_type. Now, we use helper functions
that are sensitive to sizeof(DataType)
Configuration:
DEBUG=: (opt) same layouts as trunk for RefData & TypedValue
DEBUG=1: (dbg) new RefData layout (m_tv doesn't overlap RefData::_count)
PACKED_TV=1, DEBUG=*: new RefData and TypedValue layout.
Our ext_hhvm generated code is casting TypedValue* to Value*
on the assumption that the offset of TypedValue::m_data is 0.
Fix this assumption, and also while in the same code, replace
some (t == KindOfString || t == KindOfStaticString) with
IS_STATIC_STRING(t), which does a single bit test instead of
two comparisons.
Most of this is pretty boring and mechanical. I added
VectorProp and VectorElem flags to help deal with the increasing
number of vector-related opcodes.
This change is mostly for FB internal organizational reasons.
Building is not effected beyond the fact that the target now
lands in hphp/hhvm/hhvm rather than src/hhvm/hhvm.
smith