[llvm] [SLP]Fix loads sorting for loads from diffrent basic blocks (PR #111521)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-transforms

Author: Alexey Bataev (alexey-bataev)

<details>
<summary>Changes</summary>

Patch fixes lookup for loads from different basic blocks. Originally,
the code checked is the main key (combined with parent basic block) was
created, but did not include the key into LoadsMap. When the code looked for
the load pointer in LoadsMap, it skipped check for parent basic block
and could mix loads from different basic blocks (but the same underlying
pointer). Currently, it does lead to any issues, since later the code
compares parent basic blocks and sorts loads properly. But it increases
compile time and affects compile time.


---
Full diff: https://github.com/llvm/llvm-project/pull/111521.diff


2 Files Affected:

- (modified) llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp (+5-5) 
- (modified) llvm/test/Transforms/SLPVectorizer/X86/horizontal-minmax.ll (+8-8) 


``````````diff
diff --git a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
index 401597af35bdac..4ae4f185527bbd 100644
--- a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
+++ b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
@@ -18496,14 +18496,14 @@ class HorizontalReduction {
         8>
         PossibleReducedVals;
     initReductionOps(Root);
-    DenseMap<Value *, SmallVector<LoadInst *>> LoadsMap;
+    DenseMap<std::pair<size_t, Value *>, SmallVector<LoadInst *>> LoadsMap;
     SmallSet<size_t, 2> LoadKeyUsed;
 
     auto GenerateLoadsSubkey = [&](size_t Key, LoadInst *LI) {
       Key = hash_combine(hash_value(LI->getParent()), Key);
       Value *Ptr = getUnderlyingObject(LI->getPointerOperand());
-      if (LoadKeyUsed.contains(Key)) {
-        auto LIt = LoadsMap.find(Ptr);
+      if (!LoadKeyUsed.insert(Key).second) {
+        auto LIt = LoadsMap.find(std::make_pair(Key, Ptr));
         if (LIt != LoadsMap.end()) {
           for (LoadInst *RLI : LIt->second) {
             if (getPointersDiff(RLI->getType(), RLI->getPointerOperand(),
@@ -18525,8 +18525,8 @@ class HorizontalReduction {
           }
         }
       }
-      LoadKeyUsed.insert(Key);
-      LoadsMap.try_emplace(Ptr).first->second.push_back(LI);
+      LoadsMap.try_emplace(std::make_pair(Key, Ptr))
+          .first->second.push_back(LI);
       return hash_value(LI->getPointerOperand());
     };
 
diff --git a/llvm/test/Transforms/SLPVectorizer/X86/horizontal-minmax.ll b/llvm/test/Transforms/SLPVectorizer/X86/horizontal-minmax.ll
index d1f93eccc2a91d..a7201e776fb4cd 100644
--- a/llvm/test/Transforms/SLPVectorizer/X86/horizontal-minmax.ll
+++ b/llvm/test/Transforms/SLPVectorizer/X86/horizontal-minmax.ll
@@ -980,10 +980,10 @@ define i32 @maxi8_wrong_parent(i32) {
 ; SSE4-NEXT:    [[TMP5:%.*]] = load i32, ptr getelementptr inbounds ([32 x i32], ptr @arr, i64 0, i64 6), align 8
 ; SSE4-NEXT:    [[TMP6:%.*]] = load i32, ptr getelementptr inbounds ([32 x i32], ptr @arr, i64 0, i64 7), align 4
 ; SSE4-NEXT:    [[TMP7:%.*]] = call i32 @llvm.vector.reduce.smax.v4i32(<4 x i32> [[TMP4]])
-; SSE4-NEXT:    [[OP_RDX:%.*]] = icmp sgt i32 [[TMP7]], [[TMP2]]
-; SSE4-NEXT:    [[OP_RDX1:%.*]] = select i1 [[OP_RDX]], i32 [[TMP7]], i32 [[TMP2]]
-; SSE4-NEXT:    [[OP_RDX2:%.*]] = icmp sgt i32 [[TMP5]], [[TMP6]]
-; SSE4-NEXT:    [[OP_RDX3:%.*]] = select i1 [[OP_RDX2]], i32 [[TMP5]], i32 [[TMP6]]
+; SSE4-NEXT:    [[OP_RDX:%.*]] = icmp sgt i32 [[TMP7]], [[TMP5]]
+; SSE4-NEXT:    [[OP_RDX1:%.*]] = select i1 [[OP_RDX]], i32 [[TMP7]], i32 [[TMP5]]
+; SSE4-NEXT:    [[OP_RDX2:%.*]] = icmp sgt i32 [[TMP6]], [[TMP2]]
+; SSE4-NEXT:    [[OP_RDX3:%.*]] = select i1 [[OP_RDX2]], i32 [[TMP6]], i32 [[TMP2]]
 ; SSE4-NEXT:    [[OP_RDX4:%.*]] = icmp sgt i32 [[OP_RDX1]], [[OP_RDX3]]
 ; SSE4-NEXT:    [[OP_RDX5:%.*]] = select i1 [[OP_RDX4]], i32 [[OP_RDX1]], i32 [[OP_RDX3]]
 ; SSE4-NEXT:    [[OP_RDX6:%.*]] = icmp sgt i32 [[OP_RDX5]], [[TMP3]]
@@ -999,10 +999,10 @@ define i32 @maxi8_wrong_parent(i32) {
 ; AVX-NEXT:    [[TMP5:%.*]] = load i32, ptr getelementptr inbounds ([32 x i32], ptr @arr, i64 0, i64 6), align 8
 ; AVX-NEXT:    [[TMP6:%.*]] = load i32, ptr getelementptr inbounds ([32 x i32], ptr @arr, i64 0, i64 7), align 4
 ; AVX-NEXT:    [[TMP7:%.*]] = call i32 @llvm.vector.reduce.smax.v4i32(<4 x i32> [[TMP4]])
-; AVX-NEXT:    [[OP_RDX:%.*]] = icmp sgt i32 [[TMP7]], [[TMP2]]
-; AVX-NEXT:    [[OP_RDX1:%.*]] = select i1 [[OP_RDX]], i32 [[TMP7]], i32 [[TMP2]]
-; AVX-NEXT:    [[OP_RDX2:%.*]] = icmp sgt i32 [[TMP5]], [[TMP6]]
-; AVX-NEXT:    [[OP_RDX3:%.*]] = select i1 [[OP_RDX2]], i32 [[TMP5]], i32 [[TMP6]]
+; AVX-NEXT:    [[OP_RDX:%.*]] = icmp sgt i32 [[TMP7]], [[TMP5]]
+; AVX-NEXT:    [[OP_RDX1:%.*]] = select i1 [[OP_RDX]], i32 [[TMP7]], i32 [[TMP5]]
+; AVX-NEXT:    [[OP_RDX2:%.*]] = icmp sgt i32 [[TMP6]], [[TMP2]]
+; AVX-NEXT:    [[OP_RDX3:%.*]] = select i1 [[OP_RDX2]], i32 [[TMP6]], i32 [[TMP2]]
 ; AVX-NEXT:    [[OP_RDX4:%.*]] = icmp sgt i32 [[OP_RDX1]], [[OP_RDX3]]
 ; AVX-NEXT:    [[OP_RDX5:%.*]] = select i1 [[OP_RDX4]], i32 [[OP_RDX1]], i32 [[OP_RDX3]]
 ; AVX-NEXT:    [[OP_RDX6:%.*]] = icmp sgt i32 [[OP_RDX5]], [[TMP3]]

``````````

</details>


https://github.com/llvm/llvm-project/pull/111521