Migrate metadata information from scalar to vector instructions during

SLP vectorization. Based on the code in BBVectorizer.

Fixes PR17741.

Patch by Raul Silvera, reviewed by Hal and Nadav. Reformatted by my
driving of clang-format. =]

llvm-svn: 195528

1 files changed, 37 insertions, 2 deletions

diff --git a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
index 68a7f64e7af..f2a099ac691 100644
--- a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
+++ b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
@@ -163,6 +163,37 @@ static unsigned getSameOpcode(ArrayRef<Value *> VL) {
   return Opcode;
 }
 
+/// \returns \p I after propagating metadata from \p VL.
+static Instruction *propagateMetadata(Instruction *I, ArrayRef<Value *> VL) {
+  Instruction *I0 = cast<Instruction>(VL[0]);
+  SmallVector<std::pair<unsigned, MDNode *>, 4> Metadata;
+  I0->getAllMetadataOtherThanDebugLoc(Metadata);
+
+  for (unsigned i = 0, n = Metadata.size(); i != n; ++i) {
+    unsigned Kind = Metadata[i].first;
+    MDNode *MD = Metadata[i].second;
+
+    for (int i = 1, e = VL.size(); MD && i != e; i++) {
+      Instruction *I = cast<Instruction>(VL[i]);
+      MDNode *IMD = I->getMetadata(Kind);
+
+      switch (Kind) {
+      default:
+        MD = 0; // Remove unknown metadata
+        break;
+      case LLVMContext::MD_tbaa:
+        MD = MDNode::getMostGenericTBAA(MD, IMD);
+        break;
+      case LLVMContext::MD_fpmath:
+        MD = MDNode::getMostGenericFPMath(MD, IMD);
+        break;
+      }
+    }
+    I->setMetadata(Kind, MD);
+  }
+  return I;
+}
+
 /// \returns The type that all of the values in \p VL have or null if there
 /// are different types.
 static Type* getSameType(ArrayRef<Value *> VL) {
@@ -1481,6 +1512,10 @@ Value *BoUpSLP::vectorizeTree(TreeEntry *E) {
       BinaryOperator *BinOp = cast<BinaryOperator>(VL0);
       Value *V = Builder.CreateBinOp(BinOp->getOpcode(), LHS, RHS);
       E->VectorizedValue = V;
+
+      if (Instruction *I = dyn_cast<Instruction>(V))
+        return propagateMetadata(I, E->Scalars);
+
       return V;
     }
     case Instruction::Load: {
@@ -1497,7 +1532,7 @@ Value *BoUpSLP::vectorizeTree(TreeEntry *E) {
       LI = Builder.CreateLoad(VecPtr);
       LI->setAlignment(Alignment);
       E->VectorizedValue = LI;
-      return LI;
+      return propagateMetadata(LI, E->Scalars);
     }
     case Instruction::Store: {
       StoreInst *SI = cast<StoreInst>(VL0);
@@ -1516,7 +1551,7 @@ Value *BoUpSLP::vectorizeTree(TreeEntry *E) {
       StoreInst *S = Builder.CreateStore(VecValue, VecPtr);
       S->setAlignment(Alignment);
       E->VectorizedValue = S;
-      return S;
+      return propagateMetadata(S, E->Scalars);
     }
     default:
     llvm_unreachable("unknown inst");