RFR: 8272315: Improve assert_different_registers

[Kim Barrett]

On Wed, 11 Aug 2021 11:34:26 GMT, Kim Barrett <kbarrett at openjdk.org> wrote:

> Please review this improvement to assert_different_register.
> 
> It reduces ~250 lines of repetitive code to ~10 lines, and improves the
> error message on failure by printing a duplicated registers name.
> 
> Unfortunately, this isn't enough to eliminate AbstractRegister[Impl].
> Although it seems to no longer be needed for the Oracle-supported platforms,
> the linux-arm/ppc64le/s390 platforms all use the value() function provided
> by AbstractRegisterImpl.
> 
> Testing:
> tier1 on Oracle supported platforms.
> built linux-arm/ppc64le/s390.
> 
> Locally changed a call to have a duplicate register and verified the error
> message had a useful register name.

src/hotspot/share/asm/register.hpp line 70:

> 68:   // Sort regs, so any equal entries are adjacent.
> 69:   struct Compare { ptrdiff_t operator()(R x, R y) const { return x - y; } };
> 70:   QuickSort::sort(regs, ARRAY_SIZE(regs), Compare(), false);

Sorting is kind of overkill.  Maybe I should have just use the obvious nested loop?  What do reviewers think?

-------------

PR: https://git.openjdk.java.net/jdk/pull/5083