Integrated: 8337702: Use new ForwardExceptionNode to call StubRoutines::forward_exception_entry()

[Vladimir Kozlov]

On Fri, 2 Aug 2024 06:00:22 GMT, Vladimir Kozlov <kvn at openjdk.org> wrote:

> Currently C2 uses `TailCall` node when it generates code to forward exception in C2 runtime stubs.
> `StubRoutines::forward_exception_entry()` address is passed as constant and  method pointer is `NULL`: 
> [generateOptoStub.cpp#L258](https://github.com/openjdk/jdk/blob/master/src/hotspot/share/opto/generateOptoStub.cpp#L258)
> 
> On other hand TailCall mach node uses 2 registers as parameter which is hardcoded in `Matcher`: [matcher.cpp#L828](https://github.com/openjdk/jdk/blob/master/src/hotspot/share/opto/matcher.cpp#L828)
> As result we waste two registers to pass constant and NULL.
> 
> Also incorrect relocation is used for such call because the address of `forward_exception` stub passed in register in mach node. When it is converted to `Address` for `jmp` instruction the default `external_word_type` relocation is used when `runtime_call_type` should be used. See discussion in PR [JDK-8337396](https://github.com/openjdk/jdk/pull/20412)
> 
> I added new ideal node `ForwardExceptionNode` to solve these issues. It is similar to `Rethrow` node (which mach node definition I used as template) but I kept it based on `Return` node similar to `TailCall` node.
> 
> Tested tier1-3,stress,xcomp

This pull request has now been integrated.

Changeset: 99edb4a4
Author:    Vladimir Kozlov <kvn at openjdk.org>
URL:       https://git.openjdk.org/jdk/commit/99edb4a45d6a4a871dec9c07b41b3ab66b89a4b6
Stats:     155 lines in 15 files changed: 130 ins; 2 del; 23 mod

8337702: Use new ForwardExceptionNode to call StubRoutines::forward_exception_entry()

Reviewed-by: thartmann

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PR: https://git.openjdk.org/jdk/pull/20437