[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

2 files changed, 56 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);
diff --git a/llvm/test/CodeGen/ARM/GlobalISel/arm-irtranslator.ll b/llvm/test/CodeGen/ARM/GlobalISel/arm-irtranslator.ll
index 53577dbd76f..1a0c7fd8e1d 100644
--- a/llvm/test/CodeGen/ARM/GlobalISel/arm-irtranslator.ll
+++ b/llvm/test/CodeGen/ARM/GlobalISel/arm-irtranslator.ll
@@ -699,3 +699,33 @@ define i32 @test_shufflevector_v4s32_v2s32(i32 %arg1, i32 %arg2, i32 %arg3, i32
   %res = extractelement <2 x i32> %shuffle, i32 0
   ret i32 %res
 }
+
+%struct.v2s32 = type { <2 x i32> }
+
+define i32 @test_constantstruct_v2s32() {
+; CHECK-LABEL: name: test_constantstruct_v2s32
+; CHECK: [[C1:%[0-9]+]](s32) = G_CONSTANT i32 1
+; CHECK: [[C2:%[0-9]+]](s32) = G_CONSTANT i32 2
+; CHECK: [[VEC:%[0-9]+]](<2 x s32>) = G_MERGE_VALUES [[C1]](s32), [[C2]](s32)
+; CHECK: G_EXTRACT_VECTOR_ELT [[VEC]](<2 x s32>)
+  %vec = extractvalue %struct.v2s32 {<2 x i32><i32 1, i32 2>}, 0
+  %elt = extractelement <2 x i32> %vec, i32 0
+  ret i32 %elt
+}
+
+%struct.v2s32.s32.s32 = type { <2 x i32>, i32, i32 }
+
+define i32 @test_constantstruct_v2s32_s32_s32() {
+; CHECK-LABEL: name: test_constantstruct_v2s32_s32_s32
+; CHECK: [[C1:%[0-9]+]](s32) = G_CONSTANT i32 1
+; CHECK: [[C2:%[0-9]+]](s32) = G_CONSTANT i32 2
+; CHECK: [[VEC:%[0-9]+]](<2 x s32>) = G_MERGE_VALUES [[C1]](s32), [[C2]](s32)
+; CHECK: [[C3:%[0-9]+]](s32) = G_CONSTANT i32 3
+; CHECK: [[C4:%[0-9]+]](s32) = G_CONSTANT i32 4
+; CHECK: [[CS:%[0-9]+]](s128) = G_SEQUENCE [[VEC]](<2 x s32>), 0, [[C3]](s32), 64, [[C4]](s32), 96
+; CHECK: [[EXT:%[0-9]+]](<2 x s32>) = G_EXTRACT [[CS]](s128), 0
+; CHECK: G_EXTRACT_VECTOR_ELT [[EXT]](<2 x s32>)
+  %vec = extractvalue %struct.v2s32.s32.s32 {<2 x i32><i32 1, i32 2>, i32 3, i32 4}, 0
+  %elt = extractelement <2 x i32> %vec, i32 0
+  ret i32 %elt
+}