1. 10 Oct, 2018 1 commit
    • Benedikt Meurer's avatar
      [async] Improve async function handling. · 0038e5f0
      Benedikt Meurer authored
      This change introduces new intrinsics used to desugar async functions
      in the Parser and the BytecodeGenerator, namely we introduce a new
      %_AsyncFunctionEnter intrinsic that constructs the generator object
      for the async function (and in the future will also create the outer
      promise for the async function). This generator object is internal
      and never escapes to user code, plus since async functions don't have
      a "prototype" property, we can just a single map here instead of tracking
      the prototype/initial_map on every async function. This saves one word
      per async function plus one initial_map per async function that was
      invoked at least once.
      
      We also introduce two new intrinsics %_AsyncFunctionReject, which
      rejects the outer promise with the caught exception, and another
      %_AsyncFunctionResolve, which resolves the outer promise with the
      right hand side of the `return` statement. These functions also perform
      the DevTools part of the job (aka popping from the promise stack and
      sending the debug event). This allows us to get rid of the implicit
      try-finally from async functions completely; because the finally
      block only called to the %AsyncFunctionPromiseRelease builtin, which
      was used to inform DevTools.
      
      In essence we now turn an async function like
      
      ```js
      async function f(x) { return await bar(x); }
      ```
      
      into something like this (in Parser and BytecodeGenerator respectively):
      
      ```
      function f(x) {
        .generator_object = %_AsyncFunctionEnter(.closure, this);
        .promise = %AsyncFunctionCreatePromise();
        try {
          .tmp = await bar(x);
          return %_AsyncFunctionResolve(.promise, .tmp);
        } catch (e) {
          return %_AsyncFunctionReject(.promise, e);
        }
      }
      ```
      
      Overall the bytecode for async functions gets significantly shorter
      already (and will get even shorter once we put the outer promise into
      the async function generator object). For example the bytecode for a
      simple async function
      
      ```js
      async function f(x) { return await x; }
      ```
      
      goes from 175 bytes to 110 bytes (a ~38% reduction in size), which
      is in particular due to the simplification around the try-finally
      removal.
      
      Overall this seems to improve the doxbee-async-es2017-native test by
      around 2-3%. On the test case mentioned in v8:8276 we go from
      1124ms to 441ms, which corresponds to a 60% reduction in total
      execution time!
      
      Tbr: marja@chromium.org
      Bug: v8:7253, v8:7522, v8:8276
      Cq-Include-Trybots: luci.chromium.try:linux_chromium_headless_rel;luci.chromium.try:linux_chromium_rel_ng;master.tryserver.blink:linux_trusty_blink_rel
      Change-Id: Id29dc92de7490b387ff697860c900cee44c9a7a4
      Reviewed-on: https://chromium-review.googlesource.com/c/1269041
      Commit-Queue: Benedikt Meurer <bmeurer@chromium.org>
      Reviewed-by: 's avatarBenedikt Meurer <bmeurer@chromium.org>
      Reviewed-by: 's avatarSathya Gunasekaran <gsathya@chromium.org>
      Reviewed-by: 's avatarRoss McIlroy <rmcilroy@chromium.org>
      Reviewed-by: 's avatarJaroslav Sevcik <jarin@chromium.org>
      Reviewed-by: 's avatarMaya Lekova <mslekova@chromium.org>
      Reviewed-by: 's avatarYang Guo <yangguo@chromium.org>
      Cr-Commit-Position: refs/heads/master@{#56502}
      0038e5f0
  2. 22 Jan, 2018 1 commit
  3. 18 Jul, 2017 1 commit
  4. 14 Jul, 2017 2 commits
    • Alexey Kozyatinskiy's avatar
      [inspector] improve return position of explicit return in non-async function · 08965860
      Alexey Kozyatinskiy authored
      Goal of this CL: explicit return from non-async function has position after
      return expression as return position (will unblock [1]).
      
      BytecodeArrayBuilder has SetStatementPosition and SetExpressionPosition methods.
      If one of these methods is called then next generated bytecode will get passed
      position. It's general treatment for most cases.
      Unfortunately it doesn't work for Returns:
      - debugger requires source positions exactly on kReturn bytecode in stepping
        implementation,
      - BytecodeGenerator::BuildReturn and BytecodeGenerator::BuildAsyncReturn
        generates more then one bytecode and general solution will put return position
        on first generated bytecode,
      - it's not easy to split BuildReturn function into two parts to allow something
        like following in BytecodeGenerator::VisitReturnStatement since generated
        bytecodes are actually controlled by execution_control().
      ..->BuildReturnPrologue();
      ..->SetReturnPosition(stmt);
      ..->Return();
      
      In this CL we pass ReturnStatement through ExecutionControl and use it for
      position when we emit return bytecode right here.
      
      So this CL only will improve return position for returns inside of non-async
      functions, I'll address async functions later.
      
      [1] https://chromium-review.googlesource.com/c/543161/
      
      Change-Id: Iede512c120b00c209990bf50c20e7d23dc0d65db
      Reviewed-on: https://chromium-review.googlesource.com/560738
      Commit-Queue: Aleksey Kozyatinskiy <kozyatinskiy@chromium.org>
      Reviewed-by: 's avatarAdam Klein <adamk@chromium.org>
      Reviewed-by: 's avatarMichael Starzinger <mstarzinger@chromium.org>
      Reviewed-by: 's avatarRoss McIlroy <rmcilroy@chromium.org>
      Reviewed-by: 's avatarJakob Gruber <jgruber@chromium.org>
      Cr-Commit-Position: refs/heads/master@{#46687}
      08965860
    • Caitlin Potter's avatar
      [async-await] desugar Await in BytecodeGenerator · 8b5b444a
      Caitlin Potter authored
      This includes several changes. From most to least interesting:
      
      - No longer implement AwaitExpressions using a do-expression.
      - Reduces frame-size of async generators by not allocating temporary
        variables to hold results of Await epxressions.
      - Streamline and reduce generated bytecodes for Await.
      - Debugger no longer emits a debug::kCallBreakLocation breakpoint for
      the JS-builtin call performed for Await, and instead only emits such
      a breakpoint if the operand of Await is actually a call.
      - Push fewer parameters to Await* builtins, using the receiver for the
        first parameter (possible now that the CallRuntime invocation not
        part of the AST).
      - Adds a new Await AST node. No new members or anything, but it seemed
        palatable to avoid having `if (is_await())` in a number of
        VisitSuspend functions.
      
      BUG=v8:5855, v8:5099, v8:4483
      R=rmcilroy@chromium.org, kozyatinskiy@chromium.org, yangguo@chromium.org
      TBR=bmeurer@chromium.org
      
      Change-Id: I9cd3fda99cd40295c04fdf1aea01b5d83fac6caf
      Reviewed-on: https://chromium-review.googlesource.com/558806
      Commit-Queue: Georg Neis <neis@chromium.org>
      Reviewed-by: 's avatarGeorg Neis <neis@chromium.org>
      Reviewed-by: 's avatarRoss McIlroy <rmcilroy@chromium.org>
      Reviewed-by: 's avatarTobias Tebbi <tebbi@chromium.org>
      Reviewed-by: 's avatarAleksey Kozyatinskiy <kozyatinskiy@chromium.org>
      Cr-Commit-Position: refs/heads/master@{#46666}
      8b5b444a
  5. 31 May, 2017 1 commit