This adds support to the KeyedLoadIC to ignore out of bounds accesses
for Strings and return undefined instead. We add a dedicated bit to the
Smi handler to encode the OOB state and have TurboFan generate appropriate
code for that case as well. This is mostly useful when programs
accidentially access past the length of a string, which was observed and
fixed for example in Babel recently, see
https://github.com/babel/babel/pull/6589
for details. The idea is to also extend this mechanism to Arrays and
maybe other receivers, as reading beyond the length is also often used
in jQuery and other popular libraries.
Note that this is considered a mitigation for a performance cliff and
not a general optimization of OOB accesses. These should still be
avoided and handled properly instead.
This seems to further improve the babel test on the web-tooling-benchmark
by around 1%, because the OOB access no longer turns the otherwise
MONOMORPHIC access into MEGAMORPHIC state.
Bug: v8:6936, v8:7014
Change-Id: I9df03304e056d7001a65da8e9621119f8e9bb55b
Reviewed-on: https://chromium-review.googlesource.com/744022
Commit-Queue: Benedikt Meurer <bmeurer@chromium.org>
Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#49049}
1. Replaces --crankshaft with --opt in tests.
2. Also fixes presubmit to check for --opt flag when
assertOptimized is used.
3. Updates testrunner/local/variants.py and
v8_foozie.py to use --opt flag.
This would mean, nooptimize variant means there are
no optimizations. Not even with %OptimizeFunctionOnNextCall.
Bug:v8:6325
Change-Id: I638e743d0773a6729c6b9749e2ca1e2537f12ce6
Reviewed-on: https://chromium-review.googlesource.com/490206
Commit-Queue: Mythri Alle <mythria@chromium.org>
Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#44985}
This CL adds --crankshaft and --no-always-opt flags to the tests that use
assertOptimized() and assertUnoptimized() respectively.
This CL also adds presubmit checks that ensure that tests have the proper
flags set.
BUG=v8:5890
Review-Url: https://codereview.chromium.org/2653753007
Cr-Commit-Position: refs/heads/master@{#42709}
The mentioned asserts did not work properly with interpreted and turbofanned functions.
To fix this issue %GetOptimizationStatus() now returns a set of flags instead of a single value.
This CL also adds more helper functions to mjsunit, like isNeverOptimize(), isAlwaysOptimize(),
isOptimized(fun), etc.
BUG=v8:5890
Review-Url: https://codereview.chromium.org/2654733004
Cr-Commit-Position: refs/heads/master@{#42703}
We need to check the KeyedLoadIC state to guard against potential
deoptimization loops due to out-of-bounds accesses, because the IC
system uses the MEGAMORPHIC state to also signal that there was an
out-of-bounds access already.
R=jarin@chromium.org
Review-Url: https://codereview.chromium.org/2443893002
Cr-Commit-Position: refs/heads/master@{#40525}
