[llvm] 30463bc - [SLP]Do not count perfect diamond matches for gathers several times.

[Alexey Bataev via llvm-commits]

Author: Alexey Bataev
Date: 2021-05-10T07:08:07-07:00
New Revision: 30463bc3f1839e8a238be4c137e2356f3cca2771

URL: https://github.com/llvm/llvm-project/commit/30463bc3f1839e8a238be4c137e2356f3cca2771
DIFF: https://github.com/llvm/llvm-project/commit/30463bc3f1839e8a238be4c137e2356f3cca2771.diff

LOG: [SLP]Do not count perfect diamond matches for gathers several times.

Need to remove the old code for avoiding double counting of the gather
nodes with perfect diamond matches within the tree after we started
detecting perfect/shuffled matching in the previous patch D100495. We
may skip the cost for such nodes completely.

Differential Revision: https://reviews.llvm.org/D102023

Added: 
    

Modified: 
    llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
    llvm/test/Transforms/SLPVectorizer/AArch64/gather-cost.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
index 22e090fd1d7c..e656b189c779 100644
--- a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
+++ b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
@@ -4233,27 +4233,6 @@ InstructionCost BoUpSLP::getTreeCost() {
   for (unsigned I = 0, E = VectorizableTree.size(); I < E; ++I) {
     TreeEntry &TE = *VectorizableTree[I].get();
 
-    // We create duplicate tree entries for gather sequences that have multiple
-    // uses. However, we should not compute the cost of duplicate sequences.
-    // For example, if we have a build vector (i.e., insertelement sequence)
-    // that is used by more than one vector instruction, we only need to
-    // compute the cost of the insertelement instructions once. The redundant
-    // instructions will be eliminated by CSE.
-    //
-    // We should consider not creating duplicate tree entries for gather
-    // sequences, and instead add additional edges to the tree representing
-    // their uses. Since such an approach results in fewer total entries,
-    // existing heuristics based on tree size may yield 
diff erent results.
-    //
-    if (TE.State == TreeEntry::NeedToGather &&
-        std::any_of(std::next(VectorizableTree.begin(), I + 1),
-                    VectorizableTree.end(),
-                    [TE](const std::unique_ptr<TreeEntry> &EntryPtr) {
-                      return EntryPtr->State == TreeEntry::NeedToGather &&
-                             EntryPtr->isSame(TE.Scalars);
-                    }))
-      continue;
-
     InstructionCost C = getEntryCost(&TE);
     Cost += C;
     LLVM_DEBUG(dbgs() << "SLP: Adding cost " << C

diff  --git a/llvm/test/Transforms/SLPVectorizer/AArch64/gather-cost.ll b/llvm/test/Transforms/SLPVectorizer/AArch64/gather-cost.ll
index 31c63d31f4df..57db62ace206 100644
--- a/llvm/test/Transforms/SLPVectorizer/AArch64/gather-cost.ll
+++ b/llvm/test/Transforms/SLPVectorizer/AArch64/gather-cost.ll
@@ -10,7 +10,7 @@ target triple = "aarch64--linux-gnu"
 ; REMARK-LABEL: Function: gather_multiple_use
 ; REMARK:       Args:
 ; REMARK-NEXT:    - String: 'Vectorized horizontal reduction with cost '
-; REMARK-NEXT:    - Cost: '-16'
+; REMARK-NEXT:    - Cost: '-7'
 ;
 ; REMARK-NOT: Function: gather_load