[PATCH] D145667: [Xtensa] Lower stack operations.

[Andrei Safronov via Phabricator via llvm-commits]

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Implement lowering of dynamic_stackalloc, stacksave, stackrestore.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D145667

Files:
  llvm/lib/Target/Xtensa/XtensaISelLowering.cpp
  llvm/lib/Target/Xtensa/XtensaISelLowering.h


Index: llvm/lib/Target/Xtensa/XtensaISelLowering.h
===================================================================
--- llvm/lib/Target/Xtensa/XtensaISelLowering.h
+++ llvm/lib/Target/Xtensa/XtensaISelLowering.h
@@ -79,6 +79,10 @@
   SDValue LowerJumpTable(JumpTableSDNode *JT, SelectionDAG &DAG) const;
   SDValue LowerConstantPool(ConstantPoolSDNode *CP, SelectionDAG &DAG) const;
 
+  SDValue LowerDYNAMIC_STACKALLOC(SDValue Op, SelectionDAG &DAG) const;
+  SDValue LowerSTACKSAVE(SDValue Op, SelectionDAG &DAG) const;
+  SDValue LowerSTACKRESTORE(SDValue Op, SelectionDAG &DAG) const;
+
   SDValue getAddrPCRel(SDValue Op, SelectionDAG &DAG) const;
 
   CCAssignFn *CCAssignFnForCall(CallingConv::ID CC, bool IsVarArg) const;
Index: llvm/lib/Target/Xtensa/XtensaISelLowering.cpp
===================================================================
--- llvm/lib/Target/Xtensa/XtensaISelLowering.cpp
+++ llvm/lib/Target/Xtensa/XtensaISelLowering.cpp
@@ -75,6 +75,12 @@
   setOperationAction(ISD::BlockAddress, PtrVT, Custom);
   setOperationAction(ISD::JumpTable, PtrVT, Custom);
 
+  // Implement custom stack allocations
+  setOperationAction(ISD::DYNAMIC_STACKALLOC, PtrVT, Custom);
+  // Implement custom stack save and restore
+  setOperationAction(ISD::STACKSAVE, MVT::Other, Custom);
+  setOperationAction(ISD::STACKRESTORE, MVT::Other, Custom);
+
   // Compute derived properties from the register classes
   computeRegisterProperties(STI.getRegisterInfo());
 }
@@ -664,6 +670,43 @@
   return getAddrPCRel(Result, DAG);
 }
 
+SDValue XtensaTargetLowering::LowerSTACKSAVE(SDValue Op,
+                                             SelectionDAG &DAG) const {
+  unsigned sp = Xtensa::SP;
+  return DAG.getCopyFromReg(Op.getOperand(0), SDLoc(Op), sp, Op.getValueType());
+}
+
+SDValue XtensaTargetLowering::LowerSTACKRESTORE(SDValue Op,
+                                                SelectionDAG &DAG) const {
+  unsigned sp = Xtensa::SP;
+  return DAG.getCopyToReg(Op.getOperand(0), SDLoc(Op), sp, Op.getOperand(1));
+}
+
+SDValue XtensaTargetLowering::LowerDYNAMIC_STACKALLOC(SDValue Op,
+                                                      SelectionDAG &DAG) const {
+  SDValue Chain = Op.getOperand(0); // Legalize the chain.
+  SDValue Size = Op.getOperand(1);  // Legalize the size.
+  EVT VT = Size->getValueType(0);
+  SDLoc DL(Op);
+
+  // Round up Size to 32
+  SDValue Size1 =
+      DAG.getNode(ISD::ADD, DL, VT, Size, DAG.getConstant(31, DL, MVT::i32));
+  SDValue SizeRoundUp =
+      DAG.getNode(ISD::AND, DL, VT, Size1, DAG.getConstant(~31, DL, MVT::i32));
+
+  unsigned SPReg = Xtensa::SP;
+  SDValue SP = DAG.getCopyFromReg(Chain, DL, SPReg, VT);
+  SDValue NewSP = DAG.getNode(ISD::SUB, DL, VT, SP, SizeRoundUp); // Value
+  Chain = DAG.getCopyToReg(SP.getValue(1), DL, SPReg, NewSP); // Output chain
+
+  SDValue NewVal = DAG.getCopyFromReg(Chain, DL, SPReg, MVT::i32);
+  Chain = NewVal.getValue(1);
+
+  SDValue Ops[2] = {NewVal, Chain};
+  return DAG.getMergeValues(Ops, DL);
+}
+
 SDValue XtensaTargetLowering::LowerOperation(SDValue Op,
                                              SelectionDAG &DAG) const {
   switch (Op.getOpcode()) {
@@ -679,6 +722,12 @@
     return LowerJumpTable(cast<JumpTableSDNode>(Op), DAG);
   case ISD::ConstantPool:
     return LowerConstantPool(cast<ConstantPoolSDNode>(Op), DAG);
+  case ISD::STACKSAVE:
+    return LowerSTACKSAVE(Op, DAG);
+  case ISD::STACKRESTORE:
+    return LowerSTACKRESTORE(Op, DAG);
+  case ISD::DYNAMIC_STACKALLOC:
+    return LowerDYNAMIC_STACKALLOC(Op, DAG);
   default:
     llvm_unreachable("Unexpected node to lower");
   }


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