Automated Code Change

PiperOrigin-RevId: 868470196

Migrate xls::down_cast to use absl::down_cast.

The xls::down_cast functions are now implemented as direct calls to absl::down_cast and are marked with ABSL_DEPRECATE_AND_INLINE.

Note that we also bump our abseil dep to grab a newer version with absl::down_cast.

PiperOrigin-RevId: 866676858

Update more tests in proc lowering block eval PSC test to work.

PiperOrigin-RevId: 866099089

Integrate LLVM at llvm/llvm-project@b4b8d4e5d062

Updates LLVM usage to match
[b4b8d4e5d062](https://github.com/llvm/llvm-project/commit/b4b8d4e5d062)

PiperOrigin-RevId: 865658424

Ensure aot-compiler works with targets where proc/function and block …

Fix Codegen() in v1.5 to return the pipeline metrics and residual data.

This gets codegen_main_test to pass against 1.5 aside from the necessary golden file changes.

PiperOrigin-RevId: 864582524

Don't lower an unscheduled proc to a block in codegen 1.5 when pipeli…

Fix parser bug with builtin function using builtin struct.

The issue was that we add the binding of the struct name twice, binding it first to the NameDef and then refining it to point to the StructDef. The special handling in bindings.h for the builtins module was not precise enough and would cause it to ignore the redefinition, leaving the name unexpectedly bound to the NameDef instead of the StructDef.

PiperOrigin-RevId: 863021072

Get eval_proc_main tests to work when codegen 1.5 is turned on by def…

Enable sharing of state elements between continuation values and stat…