RFR: 8274328: C2: Redundant CFG edges fixup in block ordering [v2]

[Vladimir Kozlov]

On Mon, 1 Nov 2021 07:40:40 GMT, Yi Yang <yyang at openjdk.org> wrote:

>> I think Trace::fixup_blocks is redundant because PhaseCFG::fixup_flow will nevertheless fix up the CFG flow(i.e. flip successor blocks of IfNode) right after PhaseBlockLayout pass, we can remove this step when doing PhaseBlockLayout pass.(Testing: jtreg/compiler/c2, presubmit test)
>> 
>> https://github.com/openjdk/jdk/blob/5ec1cdcaf39229a7d2457313600b0dc2bf8c6453/src/hotspot/share/opto/compile.cpp#L2765
>> 
>> https://github.com/openjdk/jdk/blob/5ec1cdcaf39229a7d2457313600b0dc2bf8c6453/src/hotspot/share/opto/block.cpp#L1679
>> 
>> https://github.com/openjdk/jdk/blob/5ec1cdcaf39229a7d2457313600b0dc2bf8c6453/src/hotspot/share/opto/block.cpp#L908-L916
>
> Yi Yang has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains three additional commits since the last revision:
> 
>  - use swap(ref,ref)
>  - Merge branch 'master' into blockordering
>  - 8274328: C2: Redundant CFG edges fixup in block ordering

Looks good.

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Marked as reviewed by kvn (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/5705