8341611: [REDO] AArch64: Clean up IndOffXX type and let legitimize_address() fix out-of-range operands

[fg1417]

IndOffXX types don't do us any good. It would be simpler and faster to match a general-purpose IndOff type then let legitimize_address() fix any out-of-range operands. That'd reduce the size of the match rules and the time to run them.

This patch simplifies the definitions of immXOffset with an estimated range. Whether an immediate can be encoded in a LDR/STR instructions as an offset will be determined in the phase of code-emitting. Meanwhile, we add necessary legitimize_address() in the phase of matcher for all LDR/STR instructions using the new IndOff memory operands (fix JDK-8341437).

After this clean-up, memory operands matched with IndOff may require extra code emission (effectively a lea) before the address can be used. So we also modify the code about looking up precise offset of load/store instruction for implicit null check (fix JDK-8340646). On aarch64 platform, we will use the beginning offset of the last instruction in the instruction clause emitted for a load/store machine node. Because LDR/STR is always the last one emitted, no matter what addressing mode the load/store operations finally use.

Tier 1 - 3 passed on Macos-aarch64 with or without the vm option -XX:+UseZGC.

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• JDK-8341611: [REDO] AArch64: Clean up IndOffXX type and let legitimize_address() fix out-of-range operands (Enhancement - P4)

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[theRealAph]

Suggested change

	// "off" is probably not within the encoding range for LDR/STR instructions
	// "off" may not be within the encoding range for LDR/STR instructions

Reads better, perhaps?

[theRealAph]

In general I like this very much.
If I were you I'd count how often legitimize_address has to split an instruction, and also count the total size of all C2 compilations over a run. I'd perhaps run jshell or javac all of java.base. Then we'd know how rare legitimize_address splitting is.
Thanks.