cmd/internal/obj/arm64: avoid unnecessary pool literal usage for load/store pairs

Implement better classification for load and store pair operations. This in
turn allows us to avoid using pool literals when the offset fits in a 24 bit
unsigned immediate. In this case, the offset can be calculated using two
add immediate instructions, rather than loading the offset from the pool
literal and then adding the offset to the base register. This requires the
same number of instructions, however avoids a load from memory and does
not require the offset to be stored in the literal pool.

Updates #59615

Change-Id: I316ec3d54f1d06ae9d930e98d0c32471775fcb26
Reviewed-on: https://go-review.googlesource.com/c/go/+/515615
Run-TryBot: Joel Sing <joel@sing.id.au>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Joedian Reid <joedian@golang.org>
Reviewed-by: Cherry Mui <cherryyz@google.com>

0 files changed, 0 insertions, 0 deletions