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: Adam Klein <adamk@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#46687}
Proposed behaviour:
- StepNext at return position go into next function call (no changes with current behavior, but implemented in v8::Debug instead of hack on inspector side);
- StepOut at return position go into next non-current function call.
We need this to have better stepping in cases with native functions, blackboxed functions and/or different embedder calls (e.g. event listeners).
New behavior could be illustrated with two examples (for more see stepping-with-natives-and-frameworks test):
- let's assume that we've blackboxed callAll function, this function just takes its arguments and call one after another:
var foo = () => 1;
callAll(foo, foo, () => 2);
If we break inside of first call of function foo. Then on..
..StepNext - we're able to reach second call of function foo,
..StepOut - we're able to reach () => 2 call.
- let's consider case with native function:
[1,2,3].map(x => x * 2)
If we break inside of first callback call, then with StepNext we can iterate through all calls of callback, with StepOut we go to next statement after .map call.
Implementation details:
- when we request break we schedule step-in function call for any step action at return position and for step-in at any position,
- when we request StepOut at return position - we mark current function as needed-to-be-ignored inside of PrepareStepIn(function) call,
- when we request StepOut at not return position - we set break at return position and ask debugger to just repeat last step action on next stepping-related break.
Design doc: https://docs.google.com/document/d/1ihXHOIhP_q-fJCA0e2EiXz_Zr3B08KMjaPifcaqZ60Q/edit
BUG=v8:6118,chromium:583193
R=dgozman@chromium.org,yangguo@chromium.org
Review-Url: https://codereview.chromium.org/2758483002
Cr-Commit-Position: refs/heads/master@{#44028}
