[AArch64] Add FeatureFuseAddSub2RegAndConstOne for Ampere1A

[ptomsich]

Ampere1A introduced the Fusion for A+B+1/A-B-1.
However, the Feature flag to enable that fusion-case never was added to TuneAmpere1A.
This commit corrects that omission.

[llvmbot]

@llvm/pr-subscribers-backend-aarch64

Author: Philipp Tomsich (ptomsich)

Changes

Ampere1A introduced the Fusion for A+B+1/A-B-1.
However, the Feature flag to enable that fusion-case never was added to TuneAmpere1A.
This commit corrects that omission.

---

Full diff: https://github.com/llvm/llvm-project/pull/81295.diff

1 Files Affected:

• (modified) llvm/lib/Target/AArch64/AArch64.td (+1)

diff --git a/llvm/lib/Target/AArch64/AArch64.td b/llvm/lib/Target/AArch64/AArch64.td
index 02fb01caf7e801..ea0c498263411d 100644
--- a/llvm/lib/Target/AArch64/AArch64.td
+++ b/llvm/lib/Target/AArch64/AArch64.td
@@ -1372,6 +1372,7 @@ def TuneAmpere1A : SubtargetFeature<"ampere1a", "ARMProcFamily", "Ampere1A",
                                     FeatureFuseAddress,
                                     FeatureFuseLiterals,
                                     FeatureFuseLiterals,
+                                    FeatureFuseAddSub2RegAndConstOne,
                                     FeatureStorePairSuppress,
                                     FeatureLdpAlignedOnly,
                                     FeatureStpAlignedOnly]>;

[jthackray]

LGTM

[davemgreen]

Changes like this should ideally have a test-case. Hopefully that is as simple as adding a new check line to one of the existing tests like llvm/test/CodeGen/AArch64/macro-fusion-addsub-2reg-const1.mir?