[PATCH] D89823: [AArch64][GlobalISel] Move imm adjustment for G_ICMP to post-legalizer lowering

[Jessica Paquette via Phabricator via llvm-commits]

paquette added inline comments.


================
Comment at: llvm/test/CodeGen/AArch64/GlobalISel/select-arith-immed-compare.mir:31
-    %1:gpr(s32) = G_CONSTANT i32 4097
-    %4:gpr(s32) = G_ICMP intpred(slt), %0(s32), %1
-    %5:gpr(s32) = G_CONSTANT i32 1
----------------
aemerson wrote:
> Can we have some end-to-end tests that show that the MIR that we previously had being selected to CSINCWr still selects to the same output if we now go through lowering->select? Don't have to cover all the cases but to show the mechanism still works.
> 
> Maybe we'll need to use .ll tests for this, not sure.
To avoid a .ll test we could do something like this:

```
 llc -mtriple=aarch64 -start-before=aarch64-postlegalizer-lowering -stop-after=instruction-select -verify-machineinstrs
```

A slightly hackier, but more pointed version would be:

```
 llc -mtriple=aarch64 -run-pass=aarch64-postlegalizer-lowering -run-pass=instruction-select -verify-machineinstrs
```

(IIRC this works)

>From the perspective that we'd only run aarch64-postlegalizer-lowering and instruction-select, I guess this is better. We'd have to use regbankselected MIR though, which is a little wonky. Not sure if that's something that we'd want to support in the future.

Preferences? (I could also just take the .ll test route, or add a GISel checkline to an existing .ll test somewhere probably)


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D89823/new/

https://reviews.llvm.org/D89823