[llvm] [SLP] Add test to demonstrate ordering changes in vectorizeStores() refactor (PR #196018)

[Ryan Buchner via llvm-commits]

https://github.com/bababuck created https://github.com/llvm/llvm-project/pull/196018

Test is for #193616. Because this test has two overlapping chains with different VFs, when the ordering that they are attempted to vectorize in changes, the result will change since the smaller chain cannot vectorize if the larger chain hasn't already vectorized due to the extract costs.

>From 4b5d4814f7914f05003242fe469d518dc5bdae34 Mon Sep 17 00:00:00 2001
From: bababuck <buchner.ryan at gmail.com>
Date: Tue, 28 Apr 2026 14:23:06 -0700
Subject: [PATCH] [SLP] Add test to demonstrate ordering changes in
 vectorizeStores() refactor

---
 .../SLPVectorizer/RISCV/load-store.ll         | 50 +++++++++++++++++++
 1 file changed, 50 insertions(+)

diff --git a/llvm/test/Transforms/SLPVectorizer/RISCV/load-store.ll b/llvm/test/Transforms/SLPVectorizer/RISCV/load-store.ll
index a6c5273dc4cd0..81bed1403cb61 100644
--- a/llvm/test/Transforms/SLPVectorizer/RISCV/load-store.ll
+++ b/llvm/test/Transforms/SLPVectorizer/RISCV/load-store.ll
@@ -265,3 +265,53 @@ entry:
   store i32 77, ptr %inc3, align 2
   ret void
 }
+
+define void @shared-chain-ordering(ptr %dest, ptr %p, i64 %offset) {
+; CHECK-LABEL: @shared-chain-ordering(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[INCS0:%.*]] = getelementptr inbounds i16, ptr [[DEST:%.*]], i64 [[OFFSET:%.*]]
+; CHECK-NEXT:    [[TMP0:%.*]] = load <4 x i16>, ptr [[P:%.*]], align 4
+; CHECK-NEXT:    store <4 x i16> [[TMP0]], ptr [[INCS0]], align 4
+; CHECK-NEXT:    [[TMP1:%.*]] = extractelement <4 x i16> [[TMP0]], i32 0
+; CHECK-NEXT:    store i16 [[TMP1]], ptr [[DEST]], align 4
+; CHECK-NEXT:    [[INCS:%.*]] = getelementptr inbounds i16, ptr [[DEST]], i64 1
+; CHECK-NEXT:    [[TMP2:%.*]] = extractelement <4 x i16> [[TMP0]], i32 1
+; CHECK-NEXT:    store i16 [[TMP2]], ptr [[INCS]], align 2
+; CHECK-NEXT:    ret void
+;
+; DEFAULT-LABEL: @shared-chain-ordering(
+; DEFAULT-NEXT:  entry:
+; DEFAULT-NEXT:    [[INCS0:%.*]] = getelementptr inbounds i16, ptr [[DEST:%.*]], i64 [[OFFSET:%.*]]
+; DEFAULT-NEXT:    [[TMP0:%.*]] = load <4 x i16>, ptr [[P:%.*]], align 4
+; DEFAULT-NEXT:    store <4 x i16> [[TMP0]], ptr [[INCS0]], align 4
+; DEFAULT-NEXT:    [[TMP1:%.*]] = extractelement <4 x i16> [[TMP0]], i32 0
+; DEFAULT-NEXT:    store i16 [[TMP1]], ptr [[DEST]], align 4
+; DEFAULT-NEXT:    [[INCS:%.*]] = getelementptr inbounds i16, ptr [[DEST]], i64 1
+; DEFAULT-NEXT:    [[TMP2:%.*]] = extractelement <4 x i16> [[TMP0]], i32 1
+; DEFAULT-NEXT:    store i16 [[TMP2]], ptr [[INCS]], align 2
+; DEFAULT-NEXT:    ret void
+;
+entry:
+  %e0 = load i16, ptr %p, align 4
+  %inc = getelementptr inbounds i16, ptr %p, i64 1
+  %e1 = load i16, ptr %inc, align 2
+  %inc1 = getelementptr inbounds i16, ptr %p, i64 2
+  %e2 = load i16, ptr %inc1, align 2
+  %inc2 = getelementptr inbounds i16, ptr %p, i64 3
+  %e3 = load i16, ptr %inc2, align 2
+
+  %incs0 = getelementptr inbounds i16, ptr %dest, i64 %offset
+  store i16 %e0, ptr %incs0, align 4
+  %incs1 = getelementptr inbounds i16, ptr %incs0, i64 1
+  store i16 %e1, ptr %incs1, align 2
+  %incs2 = getelementptr inbounds i16, ptr %incs0, i64 2
+  store i16 %e2, ptr %incs2, align 2
+  %incs3 = getelementptr inbounds i16, ptr %incs0, i64 3
+  store i16 %e3, ptr %incs3, align 2
+
+  store i16 %e0, ptr %dest, align 4
+  %incs = getelementptr inbounds i16, ptr %dest, i64 1
+  store i16 %e1, ptr %incs, align 2
+
+  ret void
+}