RFR: 8377726: Remove unused macros in register.hpp

[Albert Mingkun Yang]

On Thu, 12 Feb 2026 06:06:14 GMT, Kim Barrett <kbarrett at openjdk.org> wrote:

> Please review this change to remove some unused (or nearly unused) macros in
> share/asm/register.hpp. This change also simplifies the zero definition of
> noreg to render one of the macros no longer used.
> 
> Testing: mach5 tier1 and GHA Sanity Tests.
> The GHA testing failed to build on Alpine Linux because of the unrelated
> https://bugs.openjdk.org/browse/JDK-8377707

src/hotspot/share/asm/register.hpp line 52:

> 50: // Macros to help define all kinds of registers
> 51: 
> 52: #ifdef USE_POINTERS_TO_REGISTER_IMPL_ARRAY

Why `ifndef` -> `ifdef`?

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PR Review Comment: https://git.openjdk.org/jdk/pull/29685#discussion_r2821672091