[llvm] [GISel][AArch64] Scalarize i128 bitreverse instructions. Added tests for i128 and v2i128 bitreverse (PR #142621)

[via llvm-commits]

https://github.com/jyli0116 created https://github.com/llvm/llvm-project/pull/142621

v2i128 bitreverse previously wasn't being scalarized as it should be. Also added tests for i128 and v2i128 bitreverse

>From 32c0713db53d730b36d591a978efde5b1f693601 Mon Sep 17 00:00:00 2001
From: Yu Li <yu.li at arm.com>
Date: Tue, 3 Jun 2025 14:50:28 +0000
Subject: [PATCH] [GISel][AArch64] Scalarize i128 bitreverse instructions.
 Added tests for i128 and v2i128 bitreverse

---
 .../AArch64/GISel/AArch64LegalizerInfo.cpp    |  1 +
 llvm/test/CodeGen/AArch64/bitreverse.ll       | 29 +++++++++++++++++++
 2 files changed, 30 insertions(+)

diff --git a/llvm/lib/Target/AArch64/GISel/AArch64LegalizerInfo.cpp b/llvm/lib/Target/AArch64/GISel/AArch64LegalizerInfo.cpp
index 93f4bc423b63c..12843e16d0da1 100644
--- a/llvm/lib/Target/AArch64/GISel/AArch64LegalizerInfo.cpp
+++ b/llvm/lib/Target/AArch64/GISel/AArch64LegalizerInfo.cpp
@@ -370,6 +370,7 @@ AArch64LegalizerInfo::AArch64LegalizerInfo(const AArch64Subtarget &ST)
       .clampNumElements(0, v4s16, v8s16)
       .clampNumElements(0, v2s32, v4s32)
       .clampNumElements(0, v2s64, v2s64)
+      .scalarizeIf(scalarOrEltWiderThan(0, 64), 0)
       .moreElementsToNextPow2(0)
       .lower();
 
diff --git a/llvm/test/CodeGen/AArch64/bitreverse.ll b/llvm/test/CodeGen/AArch64/bitreverse.ll
index c1ca39d87105e..9e2228aa47c63 100644
--- a/llvm/test/CodeGen/AArch64/bitreverse.ll
+++ b/llvm/test/CodeGen/AArch64/bitreverse.ll
@@ -72,6 +72,19 @@ define i64 @g_64(i64 %a) {
   ret i64 %b
 }
 
+declare i128 @llvm.bitreverse.i128(i128) readnone
+
+define i128 @g_128(i128 %a) {
+; CHECK-LABEL: g_128:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    rbit x8, x1
+; CHECK-NEXT:    rbit x1, x0
+; CHECK-NEXT:    mov x0, x8
+; CHECK-NEXT:    ret
+  %b = call i128 @llvm.bitreverse.i128(i128 %a)
+  ret i128 %b
+}
+
 declare <16 x i3> @llvm.bitreverse.v16i3(<16 x i3>) readnone
 
 define <16 x i3> @g_vec_16x3(<16 x i3> %a) {
@@ -282,3 +295,19 @@ define <4 x i64> @g_vec_4x64(<4 x i64> %a) {
   %b = call <4 x i64> @llvm.bitreverse.v4i64(<4 x i64> %a)
   ret <4 x i64> %b
 }
+
+declare <2 x i128> @llvm.bitreverse.v2i128(<2 x i128>) readnone
+
+define <2 x i128> @g_vec_2x128(<2 x i128> %a) {
+; CHECK-LABEL: g_vec_2x128:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    rbit x8, x1
+; CHECK-NEXT:    rbit x9, x3
+; CHECK-NEXT:    rbit x1, x0
+; CHECK-NEXT:    rbit x3, x2
+; CHECK-NEXT:    mov x0, x8
+; CHECK-NEXT:    mov x2, x9
+; CHECK-NEXT:    ret
+  %b = call <2 x i128> @llvm.bitreverse.v2i128(<2 x i128> %a)
+  ret <2 x i128> %b
+}