[AArch64][GlobalISel] Select negative arithmetic immediates in manual selector

Previously, we only handled negative arithmetic immediates in the imported
selector code.

Since we don't import code for, say, compares, we were missing opportunities
for things like

```
%cst:gpr(s64) = G_CONSTANT i64 -10
%cmp:gpr(s32) = G_ICMP intpred(eq), %reg0(s64), %cst
->
%adds = ADDSXri %reg0, 10, 0, implicit-def $nzcv
%cmp = CSINCWr $wzr, $wzr, 1, implicit $nzcv
```

Instead, we would have to materialize the constant and emit a SUBS.

This adds support for selection like above for SUB, SUBS, ADD, and ADDS.

This is a 0.1% geomean code size improvement on SPECINT2000 at -Os.

Differential Revision: https://reviews.llvm.org/D91108

0 files changed, 0 insertions, 0 deletions