[llvm] [GlobalIsel][NFC] Refactor ext of trunc (PR #92533)

[Jay Foad via llvm-commits]

================
@@ -735,18 +735,20 @@ def redundant_sext_inreg: GICombineRule <
 // the destination type.
 def anyext_trunc_fold: GICombineRule <
   (defs root:$root, register_matchinfo:$matchinfo),
-  (match (wip_match_opcode G_ANYEXT):$root,
-         [{ return Helper.matchCombineAnyExtTrunc(*${root}, ${matchinfo}); }]),
-  (apply [{ Helper.replaceSingleDefInstWithReg(*${root}, ${matchinfo}); }])
+  (match (G_TRUNC $input, $x),
----------------
jayfoad wrote:

`test_combine_anyext_trunc_with_hint` in `test/CodeGen/AArch64/GlobalISel/combine-ext.mir` tests this sequence:
```
    %1:_(s32) = G_TRUNC %0(s64)
    %2:_(s32) = G_ASSERT_ZEXT %1(s32), 11
    %3:_(s64) = G_ANYEXT %2(s32)
```
I would expect your new matcher to not match this. How does it work?

https://github.com/llvm/llvm-project/pull/92533