[SelectionDAG] Legalize <1 x T> vector types for atomic load

`load atomic <1 x T>` is not valid. This change legalizes vector types of atomic load via scalarization in SelectionDAG so that it can, for example, translate from `v1i32` to `i32`.

commit-id:5c36cc8c

Author: jofrn

Diff for: llvm/lib/CodeGen/SelectionDAG/LegalizeTypes.h

@@ -861,6 +861,7 @@ class LLVM_LIBRARY_VISIBILITY DAGTypeLegalizer {
   SDValue ScalarizeVecRes_ExpOp(SDNode *N);
   SDValue ScalarizeVecRes_INSERT_VECTOR_ELT(SDNode *N);
   SDValue ScalarizeVecRes_LOAD(LoadSDNode *N);
+  SDValue ScalarizeVecRes_ATOMIC_LOAD(AtomicSDNode *N);
   SDValue ScalarizeVecRes_SCALAR_TO_VECTOR(SDNode *N);
   SDValue ScalarizeVecRes_VSELECT(SDNode *N);
   SDValue ScalarizeVecRes_SELECT(SDNode *N);

Diff for: llvm/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp

@@ -60,6 +60,9 @@ void DAGTypeLegalizer::ScalarizeVectorResult(SDNode *N, unsigned ResNo) {
   case ISD::FP_ROUND:          R = ScalarizeVecRes_FP_ROUND(N); break;
   case ISD::FPOWI:             R = ScalarizeVecRes_ExpOp(N); break;
   case ISD::INSERT_VECTOR_ELT: R = ScalarizeVecRes_INSERT_VECTOR_ELT(N); break;
+  case ISD::ATOMIC_LOAD:
+    R = ScalarizeVecRes_ATOMIC_LOAD(cast<AtomicSDNode>(N));
+    break;
   case ISD::LOAD:           R = ScalarizeVecRes_LOAD(cast<LoadSDNode>(N));break;
   case ISD::SCALAR_TO_VECTOR:  R = ScalarizeVecRes_SCALAR_TO_VECTOR(N); break;
   case ISD::SIGN_EXTEND_INREG: R = ScalarizeVecRes_InregOp(N); break;
@@ -451,6 +454,18 @@ SDValue DAGTypeLegalizer::ScalarizeVecRes_INSERT_VECTOR_ELT(SDNode *N) {
   return Op;
 }
 
+SDValue DAGTypeLegalizer::ScalarizeVecRes_ATOMIC_LOAD(AtomicSDNode *N) {
+  SDValue Result = DAG.getAtomic(
+      ISD::ATOMIC_LOAD, SDLoc(N), N->getMemoryVT().getVectorElementType(),
+      N->getValueType(0).getVectorElementType(), N->getChain(), N->getBasePtr(),
+      N->getMemOperand());
+
+  // Legalize the chain result - switch anything that used the old chain to
+  // use the new one.
+  ReplaceValueWith(SDValue(N, 1), Result.getValue(1));
+  return Result;
+}
+
 SDValue DAGTypeLegalizer::ScalarizeVecRes_LOAD(LoadSDNode *N) {
   assert(N->isUnindexed() && "Indexed vector load?");
 

Diff for: llvm/test/CodeGen/X86/atomic-load-store.ll

@@ -28,3 +28,12 @@ define i32 @test3(ptr %ptr) {
   %val = load atomic i32, ptr %ptr seq_cst, align 4
   ret i32 %val
 }
+
+define <1 x i32> @atomic_vec1_i32(ptr %x) {
+; CHECK-LABEL: atomic_vec1_i32:
+; CHECK:       ## %bb.0:
+; CHECK-NEXT:    movl (%rdi), %eax
+; CHECK-NEXT:    retq
+  %ret = load atomic <1 x i32>, ptr %x acquire, align 4
+  ret <1 x i32> %ret
+}