RFR: 8292878: x86: Make scratch register usage explicit in assembler code

[Vladimir Kozlov]

On Wed, 24 Aug 2022 18:42:28 GMT, Vladimir Ivanov <vlivanov at openjdk.org> wrote:

> Improve MacroAssembler API and make scratch register usages explicit at use sites.
> 
> Different parts of JVM have different assumptions about scratch registers and
> implicit assumptions in MacroAssembler makes it harder to reason about the
> correctness of generated code.
> 
> Most of scratch register usages relate to `AddressLiteral` on x86_64.  In such case the argument is turned into a default one (with `noreg` as a default) and implementation asserts that scratch register should be provided when the address is not guaranteed to be always reachable.
> 
> Otherwise, scratch register argument is required to be explicitly provided.
> 
> The only case left (mostly) intact is `call(AddressLiteral)`, but I switched it from `rscratch` (`r10`) to `rax`.
> 
> Testing:
> - [x] hs-tier1 - hs-tier4 (w/ -XX:+-ForceUnreachable)
> - [x] x86_32 build

I hope you did not do this all by hand ;)

Good.

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Marked as reviewed by kvn (Reviewer).

PR: https://git.openjdk.org/jdk/pull/10003