[GlobalISel] IRTranslator: Translate ConstantStruct

Reviewers: qcolombet, ab, t.p.northover, aditya_nandakumar, dsanders

Reviewed By: qcolombet

Subscribers: rovka, kristof.beyls, javed.absar, igorb, llvm-commits

Differential Revision: https://reviews.llvm.org/D33317

llvm-svn: 303412

1 files changed, 26 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp b/llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp
index 77dfb13ac1f..afc18a15aa1 100644
--- a/llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp
@@ -340,6 +340,15 @@ bool IRTranslator::translateExtractValue(const User &U,
   Type *Int32Ty = Type::getInt32Ty(U.getContext());
   SmallVector<Value *, 1> Indices;
 
+  // If Src is a single element ConstantStruct, translate extractvalue
+  // to that element to avoid inserting a cast instruction.
+  if (auto CS = dyn_cast<ConstantStruct>(Src))
+    if (CS->getNumOperands() == 1) {
+      unsigned Res = getOrCreateVReg(*CS->getOperand(0));
+      ValToVReg[&U] = Res;
+      return true;
+    }
+
   // getIndexedOffsetInType is designed for GEPs, so the first index is the
   // usual array element rather than looking into the actual aggregate.
   Indices.push_back(ConstantInt::get(Int32Ty, 0));
@@ -1108,6 +1117,23 @@ bool IRTranslator::translate(const Constant &C, unsigned Reg) {
     default:
       return false;
     }
+  } else if (auto CS = dyn_cast<ConstantStruct>(&C)) {
+    // Return the element if it is a single element ConstantStruct.
+    if (CS->getNumOperands() == 1) {
+      unsigned EltReg = getOrCreateVReg(*CS->getOperand(0));
+      EntryBuilder.buildCast(Reg, EltReg);
+      return true;
+    }
+    SmallVector<unsigned, 4> Ops;
+    SmallVector<uint64_t, 4> Indices;
+    uint64_t Offset = 0;
+    for (unsigned i = 0; i < CS->getNumOperands(); ++i) {
+      unsigned OpReg = getOrCreateVReg(*CS->getOperand(i));
+      Ops.push_back(OpReg);
+      Indices.push_back(Offset);
+      Offset += MRI->getType(OpReg).getSizeInBits();
+    }
+    EntryBuilder.buildSequence(Reg, Ops, Indices);
   } else if (auto CV = dyn_cast<ConstantVector>(&C)) {
     if (CV->getNumOperands() == 1)
       return translate(*CV->getOperand(0), Reg);