[llvm] [SLPVectorizer] Make the insert/extractvector PHICompare a strict-weak ordering (PR #83571)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-transforms

Author: Benjamin Kramer (d0k)

<details>
<summary>Changes</summary>

This was tripping off STL implementations that check for it (like libc++ with debug checking). The goal of this sort is to cluster operations on the same values so preserve that property but sort everything else based on the existing numbering.

---
Full diff: https://github.com/llvm/llvm-project/pull/83571.diff


1 Files Affected:

- (modified) llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp (+5-13) 


``````````diff
diff --git a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
index cdb341efcedca3..cd5adf926d37f3 100644
--- a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
+++ b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
@@ -4392,24 +4392,16 @@ BoUpSLP::getReorderingData(const TreeEntry &TE, bool TopToBottom) {
           if (!areTwoInsertFromSameBuildVector(
                   IE1, IE2,
                   [](InsertElementInst *II) { return II->getOperand(0); }))
-            return false;
-          std::optional<unsigned> Idx1 = getInsertIndex(IE1);
-          std::optional<unsigned> Idx2 = getInsertIndex(IE2);
-          if (Idx1 == std::nullopt || Idx2 == std::nullopt)
-            return false;
-          return *Idx1 < *Idx2;
+            return I1 < I2;
+          return getInsertIndex(IE1) < getInsertIndex(IE2);
         }
       if (auto *EE1 = dyn_cast<ExtractElementInst>(FirstUserOfPhi1))
         if (auto *EE2 = dyn_cast<ExtractElementInst>(FirstUserOfPhi2)) {
           if (EE1->getOperand(0) != EE2->getOperand(0))
-            return false;
-          std::optional<unsigned> Idx1 = getExtractIndex(EE1);
-          std::optional<unsigned> Idx2 = getExtractIndex(EE2);
-          if (Idx1 == std::nullopt || Idx2 == std::nullopt)
-            return false;
-          return *Idx1 < *Idx2;
+            return I1 < I2;
+          return getInsertIndex(EE1) < getInsertIndex(EE2);
         }
-      return false;
+      return I1 < I2;
     };
     auto IsIdentityOrder = [](const OrdersType &Order) {
       for (unsigned Idx : seq<unsigned>(0, Order.size()))

``````````

</details>


https://github.com/llvm/llvm-project/pull/83571