[Xtnesa] Fix ConstantPool lowering.

Implement lowering of the aggregate and vector constants
in Global Variables like it is done in gcc.

Author: andreisfr

llvm/lib/Target/Xtensa/XtensaISelLowering.cpp

@@ -1592,11 +1592,25 @@ SDValue XtensaTargetLowering::LowerConstantPool(SDValue Op,
                                                 SelectionDAG &DAG) const {
   EVT PtrVT = Op.getValueType();
   ConstantPoolSDNode *CP = cast<ConstantPoolSDNode>(Op);
+  auto C = const_cast<Constant *>(CP->getConstVal());
+  auto T = const_cast<Type *>(CP->getType());
   SDValue Result;
 
-  if (!CP->isMachineConstantPoolEntry()) {
-    Result = DAG.getTargetConstantPool(CP->getConstVal(), PtrVT, CP->getAlign(),
-                                       CP->getOffset());
+  // Do not use constant pool for aggregate or vector constant types,
+  // in such cases create global variable
+  if (T->isAggregateType() || T->isVectorTy()) {
+    auto AFI = DAG.getMachineFunction().getInfo<XtensaMachineFunctionInfo>();
+    auto M = const_cast<Module *>(
+        DAG.getMachineFunction().getFunction().getParent());
+    auto GV = new GlobalVariable(
+        *M, T, /*isConstant=*/true, GlobalVariable::InternalLinkage, C,
+        Twine(DAG.getDataLayout().getPrivateGlobalPrefix()) + "CP" +
+            Twine(DAG.getMachineFunction().getFunctionNumber()) + "_" +
+            Twine(AFI->createCPLabelId()));
+    Result = DAG.getTargetConstantPool(GV, PtrVT, Align(4));
+  } else if (!CP->isMachineConstantPoolEntry()) {
+    Result =
+        DAG.getTargetConstantPool(C, PtrVT, CP->getAlign(), CP->getOffset());
   } else {
     report_fatal_error("This constantpool type is not supported yet");
   }

llvm/lib/Target/Xtensa/XtensaInstrInfo.td

@@ -310,6 +310,10 @@ def : Pat<(i32 (extloadi1  addr_ish1:$addr)), (L8UI addr_ish1:$addr)>;
 def : Pat<(i32 (extloadi8  addr_ish1:$addr)), (L8UI addr_ish1:$addr)>;
 def : Pat<(i32 (extloadi16 addr_ish2:$addr)), (L16UI addr_ish2:$addr)>;
 
+// Load from aggregate constant placed as Global Variable
+def : Pat<(i32 (load (add i32:$s, (Xtensa_pcrel_wrapper tconstpool:$in)))),
+          (L32I (ADD i32:$s, (L32R tconstpool:$in)), 0)>;
+
 //===----------------------------------------------------------------------===//
 // Conditional branch instructions
 //===----------------------------------------------------------------------===//
@@ -1661,6 +1665,11 @@ let AddedComplexity = 10 in
 def : Pat<(f32 (load (Xtensa_pcrel_wrapper tconstpool:$in))),
           (WFR (L32R tconstpool:$in))>;
 
+// Load from aggregate constant placed as Global Variable
+let AddedComplexity = 10 in
+def : Pat<(f32 (load (add i32:$s, (Xtensa_pcrel_wrapper tconstpool:$in)))),
+          (LSI (ADD i32:$s, (L32R tconstpool:$in)), 0)>;
+
 //===----------------------------------------------------------------------===//
 // SelectCC and BranchCC instructions with FP operands
 //===----------------------------------------------------------------------===//