RFR: 8295166: IGV: dump graph at more locations

[Roberto Castañeda Lozano]

On Tue, 10 Oct 2023 13:31:00 GMT, Daniel Lundén <duke at openjdk.org> wrote:

> This changeset
> 1. adds a number of new graph dumps for IdealGraphVisualizer (IGV):
>    - Before conditional constant propagation
>    - After register allocation
>    - After block ordering
>    - After peephole optimization
>    - After post-allocation expansion
>    - Before and after
>      - loop predication
>      - loop peeling
>      - pre/main/post loops
>      - loop unrolling
>      - range check elimination
>      - loop unswitching
>      - partial peeling
>      - split if
>      - superword
> 2. adds support for enumeration of repeated IGV graph dumps.
> 3. adjusts IGV print levels to encompass the new graph dumps. The old levels 4 and 5 are now levels 5 and 6. The new level 4 is for loop optimization dumps.
> 
> Example phase list screenshots in IGV (first at level 6, second at level 4)
> ![Screenshot from 2023-12-04 13-55-38](https://github.com/openjdk/jdk/assets/4222397/6759dc5a-9c9a-42b9-8d9e-2d0b53e76ab4) ![Screenshot from 2023-12-04 13-56-29](https://github.com/openjdk/jdk/assets/4222397/44d6a239-587b-4f7c-8ce1-f7613cb2fa35)
> 
> 
> Some notes:
> - While discussing the above changes, a separate question was brought up by @chhagedorn:
>   > On a separate note, I'm wondering how useful it is to always dump all JFR events when calling print_method(). Should this be revisited again in general?
> - The new IGV graph dump enumeration enables a number of cleanups. There is now another RFE for IGV cleanup: [JDK-8319599](https://bugs.openjdk.org/browse/JDK-8319599).
> 
> ### Testing
> #### Platforms: windows-x64, linux-x64, linux-aarch64, macosx-x64, macosx-aarch64
> - tier1, tier2, tier3, tier4, tier5.
> - Check that optimized builds (`--with-debug-level optimized`) still work.
> 
> #### Platforms: linux-x64
> - Tested that thousands of graphs are correctly opened and visualized with IGV.

src/hotspot/share/opto/compile.cpp line 2999:

> 2997:     cfg.remove_unreachable_blocks();
> 2998:     cfg.verify_dominator_tree();
> 2999: 

Nit: no need for extra line here.

src/hotspot/share/opto/compile.cpp line 3008:

> 3006:     PhasePeephole peep( _regalloc, cfg);
> 3007:     peep.do_transform();
> 3008: 

Nit: no need for extra line here.

src/hotspot/share/opto/compile.cpp line 3016:

> 3014:     TracePhase tp("postalloc_expand", &timers[_t_postalloc_expand]);
> 3015:     cfg.postalloc_expand(_regalloc);
> 3016: 

Nit: no need for extra line here.

-------------

PR Review Comment: https://git.openjdk.org/jdk/pull/16120#discussion_r1418638810
PR Review Comment: https://git.openjdk.org/jdk/pull/16120#discussion_r1418638725
PR Review Comment: https://git.openjdk.org/jdk/pull/16120#discussion_r1418638621