[PATCH] D82416: [SVE] Make Constant::getSplatValue work for scalable vector splats

[Christopher Tetreault via Phabricator via llvm-commits]

ctetreau updated this revision to Diff 274647.
ctetreau added a comment.

rebase


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D82416/new/

https://reviews.llvm.org/D82416

Files:
  llvm/lib/IR/Constants.cpp
  llvm/unittests/IR/ConstantsTest.cpp


Index: llvm/unittests/IR/ConstantsTest.cpp
===================================================================
--- llvm/unittests/IR/ConstantsTest.cpp
+++ llvm/unittests/IR/ConstantsTest.cpp
@@ -638,5 +638,34 @@
   EXPECT_FALSE(CP00U->isElementWiseEqual(CP00U0));
 }
 
+TEST(ConstantsTest, GetSplatValueRoundTrip) {
+  LLVMContext Context;
+
+  Type *FloatTy = Type::getFloatTy(Context);
+  Type *Int32Ty = Type::getInt32Ty(Context);
+  Type *Int8Ty = Type::getInt8Ty(Context);
+
+  for (unsigned Min : {1, 2, 8}) {
+    ElementCount SEC = {Min, true};
+    ElementCount FEC = {Min, false};
+
+    for (auto EC : {SEC, FEC}) {
+      for (auto *Ty : {FloatTy, Int32Ty, Int8Ty}) {
+        Constant *Zero = Constant::getNullValue(Ty);
+        Constant *One = Constant::getAllOnesValue(Ty);
+
+        for (auto *C : {Zero, One}) {
+          Constant *Splat = ConstantVector::getSplat(EC, C);
+          ASSERT_NE(nullptr, Splat);
+
+          Constant *SplatVal = Splat->getSplatValue();
+          EXPECT_NE(nullptr, SplatVal);
+          EXPECT_EQ(SplatVal, C);
+        }
+      }
+    }
+  }
+}
+
 }  // end anonymous namespace
 }  // end namespace llvm
Index: llvm/lib/IR/Constants.cpp
===================================================================
--- llvm/lib/IR/Constants.cpp
+++ llvm/lib/IR/Constants.cpp
@@ -1521,6 +1521,27 @@
     return CV->getSplatValue();
   if (const ConstantVector *CV = dyn_cast<ConstantVector>(this))
     return CV->getSplatValue(AllowUndefs);
+
+  // Check if this is a constant expression splat of the form returned by
+  // ConstantVector::getSplat()
+  const auto *Shuf = dyn_cast<ConstantExpr>(this);
+  if (Shuf && Shuf->getOpcode() == Instruction::ShuffleVector &&
+      isa<UndefValue>(Shuf->getOperand(1))) {
+
+    const auto *IElt = dyn_cast<ConstantExpr>(Shuf->getOperand(0));
+    if (IElt && IElt->getOpcode() == Instruction::InsertElement &&
+        isa<UndefValue>(IElt->getOperand(0))) {
+
+      ArrayRef<int> Mask = Shuf->getShuffleMask();
+      Constant *SplatVal = IElt->getOperand(1);
+      ConstantInt *Index = cast<ConstantInt>(IElt->getOperand(2));
+
+      if (Index->getValue() == 0 &&
+          std::all_of(Mask.begin(), Mask.end(), [](int I) { return I == 0; }))
+        return SplatVal;
+    }
+  }
+
   return nullptr;
 }
 


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