[lworld] Integrated: 8367156: [lworld] MacroAssembler::remove_frame hits "Field too big for insn"

[Marc Chevalier]

On Thu, 11 Sep 2025 14:13:41 GMT, Marc Chevalier <mchevalier at openjdk.org> wrote:

> As suspected, it's just a too big offset. We used to have a
> https://github.com/openjdk/valhalla/blob/c8d4a247861052aa6ed43125bcbe49995326938f/src/hotspot/cpu/aarch64/macroAssembler_aarch64.cpp#L6133
> 
> I changed it into
> https://github.com/openjdk/valhalla/blob/880ae47831ed7262a0d3b30b92c3645bc67e5df2/src/hotspot/cpu/aarch64/macroAssembler_aarch64.cpp#L6136
> 
> But [`ldp`](https://developer.arm.com/documentation/ddi0602/2025-06/Base-Instructions/LDP--Load-pair-of-registers-) has only a 7-bit offset. It's big, but not big enough. In some cases I've looked at, the offset can be as big as `536` which fits on 9 bits. [`ldr`](https://developer.arm.com/documentation/ddi0602/2025-06/Base-Instructions/LDR--immediate---Load-register--immediate--) supports a 9-bit offset. Let's change the `ldp` into
> 
> 
> ldr(rscratch1, Address(sp, sp_inc_offset))
> ldr(rfp, Address(sp, sp_inc_offset + wordSize))
> 
> which will be merged into one `ldp` if the offset fits.
> 
> But what if the offset is bigger than what fits on 9 bits? Well, us used to have the `ldr(rscratch1, Address(sp, sp_inc_offset))` so either we have a big problem (too big frames?) or `sp_inc_offset` was just bordeline and `sp_inc_offset + wordSize` is too big. But we still have `sp_inc_offset + wordSize == initial_framesize - 2 * wordSize` which would mean that `initial_framesize` doesn't fit on 9 bits either. Once again, that sounds like a bigger (and unlikely) problem.
> 
> Thanks,
> Marc

This pull request has now been integrated.

Changeset: 4da4927e
Author:    Marc Chevalier <mchevalier at openjdk.org>
Committer: Christian Hagedorn <chagedorn at openjdk.org>
URL:       https://git.openjdk.org/valhalla/commit/4da4927e310fe366421b47f68d5a9662abc75d88
Stats:     63 lines in 2 files changed: 62 ins; 0 del; 1 mod

8367156: [lworld] MacroAssembler::remove_frame hits "Field too big for insn"

Reviewed-by: thartmann, chagedorn

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PR: https://git.openjdk.org/valhalla/pull/1575