the .eh_frame format as part of the jitdump generated when
FLAG_perf_prof is enabled. The final goal is allowing precise unwinding
of callchains that include JITted code when profiling V8 using perf.
Unwinding information is stored in the body of code objects after the
code itself, prefixed with its length and aligned to a 8-byte boundary.
A boolean flag in the header signals its presence, resulting in zero
memory overhead when the generation of unwinding info is disabled or
no such information was attached to the code object.
A new jitdump record type (with id 4) is introduced for specifying
optional unwinding information for code load records. The EhFrameHdr
struct is also introduced, together with a constructor to initialise it
from the associated code object.
At this stage no unwinding information is written to the jitdump, but
the infrastructure for doing so is ready in place.
BUG=v8:4899
LOG=N
Review-Url: https://codereview.chromium.org/1993653003
Cr-Commit-Position: refs/heads/master@{#37296}
There are no ICs left that store their state in this field: vector based
ICs use feedback vector and the rest three (BinaryOpIC, CompareIC and
ToBooleanIC) reconstruct their state from the ExtraICState field.
This CL also removes unused InlineCacheState::DEBUG_STUB which was used
mostly in Code::is_debug_stub(). The latter now checks if the code is one
of the debug builtins instead.
BUG=chromium:618701
LOG=Y
Review-Url: https://codereview.chromium.org/2052763003
Cr-Commit-Position: refs/heads/master@{#36871}
Most maps have a small code cache (often only one entry), so this patch
optimizes memory consumption of such cases by using plain FixedArrays,
only switching to CodeCacheHashTables when the number of cached entries
gets so large that linear-scan lookups get too slow.
On loading inbox.google.com, this gets the aggregate size of all maps'
code caches (there are about 13,600 of them) from 4300 KB to 970 KB.
Review-Url: https://codereview.chromium.org/2021373002
Cr-Commit-Position: refs/heads/master@{#36681}
