1686658 - Tidy up debug output with IONFLAGS=, especially IONFLAGS=all

Status: RESOLVED FIXED

(Core :: JavaScript Engine: JIT, enhancement, P1)

Description

[Julian Seward [:jseward]]

Output with IONFLAGS=all is valuable for debugging the various JITs, but is
inconsistent and poorly sectioned, at least for the output generated when the
input is wasm and the selected compiler is Ion. This patch makes some
improvements. There is no functional change for non-debug builds. The
changes make it easier to navigate through large amounts of debug output.

Comment 1

[Julian Seward [:jseward]]

Attachment: Bug 1686658 - Tidy up debug output with IONFLAGS=, especially IONFLAGS=all. r=jandem.

Output with IONFLAGS=all is valuable for debugging the various JITs, but is
inconsistent and poorly sectioned, at least for the output generated when the
input is wasm and the selected compiler is Ion. This patch makes some
improvements. There is no functional change for non-debug builds. The
changes make it easier to navigate through large amounts of debug output.
Changes are:

• For debug printing caused by MIR optimisation (meaning, as driven by
  OptimizeMIR()), by the code generator, and by the register allocator:
  route all output by the official JitSpew family of calls, instead of an
  ad-hoc mixture of JitSpew calls and lower level printfs. This causes
  all such output to be properly prefixed with a [SomePass] style marker.
  Most of these changes are in the register allocator.

• For the debug printing caused by OptimizeMIR():

  • print a blank line before the output of each pass, so as to make it easier
    to identify the start and end of debug output for each pass. No blank
    line is emitted for passes which don't create debug output (meaning, which
    don't have their own JitSpew_SomePass selector.

  • Ensure that every pass which is run, that can emit debug output and which
    is enabled by the IONFLAGS= setting, does actually print at least one
    line, even if it is just a [SomePass] Begin message, so we can know that
    the pass actually ran. Without this, it's impossible to differentiate the
    cases "pass ran, but produced no debug output" from "pass didn't run",
    when reading debug output.

  • for the debug printing for the Range analysis pass, add some missing
    newlines.

  • In various places, add a bit of indentation so as to clarify the logical
    nesting structure of the debug output.

• In the register allocator, fine-tune the placement of blank lines so as to
  clarify the start/end of sub-phases, and convert many ad-hoc out.printf
  calls to official JitSpew calls.

• In wasm::IonCompileFunctions(), make the function start/end logging lines
  much longer, so as to make it easier to find them in large log files.

• js/src/jit/JitSpewer.h: new entry WasmBCE, for wasm bounds-check
  elimination logging.

Comment 2

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/9120167d57bd
Tidy up debug output with IONFLAGS=, especially IONFLAGS=all.  r=jandem.

Comment 3

[Alexandru Michis [:malexandru]]

https://hg.mozilla.org/mozilla-central/rev/9120167d57bd