[InstSimplify] Teach InstSimplify how to simplify extractvalue

llvm-svn: 242007

1 files changed, 41 insertions, 0 deletions

diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp
index ab5cd01ab63..ad85a3ed73c 100644
--- a/llvm/lib/Analysis/InstructionSimplify.cpp
+++ b/llvm/lib/Analysis/InstructionSimplify.cpp
@@ -3520,6 +3520,41 @@ Value *llvm::SimplifyInsertValueInst(
                                    RecursionLimit);
 }
 
+/// SimplifyExtractValueInst - Given operands for an ExtractValueInst, see if we
+/// can fold the result.  If not, this returns null.
+static Value *SimplifyExtractValueInst(Value *Agg, ArrayRef<unsigned> Idxs,
+                                       const Query &, unsigned) {
+  if (auto *CAgg = dyn_cast<Constant>(Agg))
+    return ConstantFoldExtractValueInstruction(CAgg, Idxs);
+
+  // extractvalue x, (insertvalue y, elt, n), n -> elt
+  unsigned NumIdxs = Idxs.size();
+  for (auto *IVI = dyn_cast<InsertValueInst>(Agg); IVI != nullptr;
+       IVI = dyn_cast<InsertValueInst>(IVI->getAggregateOperand())) {
+    ArrayRef<unsigned> InsertValueIdxs = IVI->getIndices();
+    unsigned NumInsertValueIdxs = InsertValueIdxs.size();
+    unsigned NumCommonIdxs = std::min(NumInsertValueIdxs, NumIdxs);
+    if (InsertValueIdxs.slice(0, NumCommonIdxs) ==
+        Idxs.slice(0, NumCommonIdxs)) {
+      if (NumIdxs == NumInsertValueIdxs)
+        return IVI->getInsertedValueOperand();
+      break;
+    }
+  }
+
+  return nullptr;
+}
+
+Value *llvm::SimplifyExtractValueInst(Value *Agg, ArrayRef<unsigned> Idxs,
+                                      const DataLayout &DL,
+                                      const TargetLibraryInfo *TLI,
+                                      const DominatorTree *DT,
+                                      AssumptionCache *AC,
+                                      const Instruction *CxtI) {
+  return ::SimplifyExtractValueInst(Agg, Idxs, Query(DL, TLI, DT, AC, CxtI),
+                                    RecursionLimit);
+}
+
 /// SimplifyPHINode - See if we can fold the given phi.  If not, returns null.
 static Value *SimplifyPHINode(PHINode *PN, const Query &Q) {
   // If all of the PHI's incoming values are the same then replace the PHI node
@@ -3929,6 +3964,12 @@ Value *llvm::SimplifyInstruction(Instruction *I, const DataLayout &DL,
                                      IV->getIndices(), DL, TLI, DT, AC, I);
     break;
   }
+  case Instruction::ExtractValue: {
+    auto *EVI = cast<ExtractValueInst>(I);
+    Result = SimplifyExtractValueInst(EVI->getAggregateOperand(),
+                                      EVI->getIndices(), DL, TLI, DT, AC, I);
+    break;
+  }
   case Instruction::PHI:
     Result = SimplifyPHINode(cast<PHINode>(I), Query(DL, TLI, DT, AC, I));
     break;