[lworld] RFR: 8327150: [lworld] Update C1 to support new value construction scheme from JEP 401

[Tobias Hartmann]

On Fri, 1 Mar 2024 20:57:08 GMT, Frederic Parain <fparain at openjdk.org> wrote:

> Fix value creation in C1, remove the old special node for value creation and out everything under the NewInstance node.
> There's also a fix in can_be_inline_klass() method that was causing a wrong behavior for acmp.

Thanks for working on this, Fred! Do all compiler tests now pass with `-XX:TieredStopAtLevel=3` or is there some work left?

src/hotspot/share/c1/c1_Compiler.cpp line 260:

> 258:     if (PrintCFGToFile) {  // borrowing flag for JDK build
> 259:       tty->print_cr("Starting C1 compilation of %s.%s", method->holder()->name()->as_utf8(), method->name()->as_utf8());
> 260:     }

Why do you need this?

src/hotspot/share/c1/c1_Instruction.hpp line 2068:

> 2066:       // FIXME: Removal of NewInlineTypeInstance instruction makes those assert hard to write
> 2067:       // assert(x->as_NewInlineTypeInstance() == nullptr || y->type() == objectNull, "Sanity check");
> 2068:       // assert(y->as_NewInlineTypeInstance() == nullptr || x->type() == objectNull, "Sanity check");

Let's remove these checks for now.

src/hotspot/share/c1/c1_Runtime1.cpp line 373:

> 371:   h->initialize(CHECK);
> 372:   oop obj = nullptr;
> 373:   if(h->is_empty_inline_type()) {

Suggestion:

  if (h->is_empty_inline_type()) {

src/hotspot/share/c1/c1_Runtime1.cpp line 374:

> 372:   oop obj = nullptr;
> 373:   if(h->is_empty_inline_type()) {
> 374:     assert(h->is_inline_klass(), "Sanity check");

Below `InlineKlass::cast` will already assert that.

src/hotspot/share/c1/c1_Runtime1.cpp line 375:

> 373:   if(h->is_empty_inline_type()) {
> 374:     assert(h->is_inline_klass(), "Sanity check");
> 375:     assert(InlineKlass::cast(h)->default_value() != nullptr, "");

This can be moved below and check `obj != nullptr` directly.

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PR Review: https://git.openjdk.org/valhalla/pull/1029#pullrequestreview-1914324112
PR Review Comment: https://git.openjdk.org/valhalla/pull/1029#discussion_r1511173608
PR Review Comment: https://git.openjdk.org/valhalla/pull/1029#discussion_r1511173264
PR Review Comment: https://git.openjdk.org/valhalla/pull/1029#discussion_r1511169072
PR Review Comment: https://git.openjdk.org/valhalla/pull/1029#discussion_r1511170599
PR Review Comment: https://git.openjdk.org/valhalla/pull/1029#discussion_r1511171181