[LoongArch] Support when the depth of __builtin_frame_address is greater than zero

[gonglingqin]

Summary

As discussed in D137541, it supports processing when the depth of
__builtin_frame_address is greater than 0 instead of reporting an error.
Unsafe calls rely on the '-Wframe-address' option for diagnosis.

[SixWeining]

LGTM and let's wait for others.

llvm/lib/Target/LoongArch/LoongArchISelLowering.cpp

 SDValue LoongArchTargetLowering::lowerFRAMEADDR(SDValue Op,
                                                 SelectionDAG &DAG) const {
   if (!isa<ConstantSDNode>(Op.getOperand(0))) {
     DAG.getContext()->emitError("argument to '__builtin_frame_address' must "
                                 "be a constant integer");
     return SDValue();
   }
 
-  // Currently only support lowering frame address for current frame.
-  if (cast<ConstantSDNode>(Op.getOperand(0))->getZExtValue() != 0) {
-    DAG.getContext()->emitError(
-        "frame address can only be determined for the current frame");
-    return SDValue();
-  }
-
   MachineFunction &MF = DAG.getMachineFunction();
   MF.getFrameInfo().setFrameAddressIsTaken(true);
-
-  return DAG.getCopyFromReg(DAG.getEntryNode(), SDLoc(Op),
-                            Subtarget.getRegisterInfo()->getFrameRegister(MF),
-                            Op.getValueType());
+  Register FrameReg = Subtarget.getRegisterInfo()->getFrameRegister(MF);
+  EVT VT = Op.getValueType();
+  SDLoc DL(Op);
+  SDValue FrameAddr = DAG.getCopyFromReg(DAG.getEntryNode(), DL, FrameReg, VT);
+  unsigned Depth = cast<ConstantSDNode>(Op.getOperand(0))->getZExtValue();
+  int GRLenInBytes = Subtarget.getGRLen() / 8;
+
+  while (Depth--) {
+    int Offset = -(GRLenInBytes * 2);
+    SDValue Ptr = DAG.getNode(ISD::ADD, DL, VT, FrameAddr,
+                              DAG.getIntPtrConstant(Offset, DL));
+    FrameAddr =
+        DAG.getLoad(VT, DL, DAG.getEntryNode(), Ptr, MachinePointerInfo());
+  }
+  return FrameAddr;
 }
 
 SDValue LoongArchTargetLowering::lowerRETURNADDR(SDValue Op,
                                                  SelectionDAG &DAG) const {
   if (verifyReturnAddressArgumentIsConstant(Op, DAG))
     return SDValue();
 
   // Currently only support lowering return address for current frame.

llvm/test/CodeGen/LoongArch/frameaddr-returnaddr-error.ll

 
 
 define ptr @non_const_depth_returnaddress(i32 %x) nounwind {
 ; CHECK: argument to '__builtin_return_address' must be a constant integer
   %1 = call ptr @llvm.returnaddress(i32 %x)
   ret ptr %1
 }
 
-define ptr @non_zero_frameaddress() nounwind {
-; CHECK: frame address can only be determined for the current frame
-  %1 = call ptr @llvm.frameaddress(i32 1)
-  ret ptr %1
-}
-
-
 define ptr @non_zero_returnaddress() nounwind {
 ; CHECK: return address can only be determined for the current frame
   %1 = call ptr @llvm.returnaddress(i32 1)
   ret ptr %1
 }
 

llvm/test/CodeGen/LoongArch/frameaddr-returnaddr.ll

 ; LA64-NEXT:    ld.d $fp, $sp, 0 # 8-byte Folded Reload
 ; LA64-NEXT:    ld.d $ra, $sp, 8 # 8-byte Folded Reload
 ; LA64-NEXT:    addi.d $sp, $sp, 16
 ; LA64-NEXT:    ret
   %1 = call ptr @llvm.frameaddress(i32 0)
   ret ptr %1
 }
 
+define ptr @test_frameaddress_2() nounwind {
+; LA32-LABEL: test_frameaddress_2:
+; LA32:       # %bb.0:
+; LA32-NEXT:    addi.w $sp, $sp, -16
+; LA32-NEXT:    st.w $ra, $sp, 12 # 4-byte Folded Spill
+; LA32-NEXT:    st.w $fp, $sp, 8 # 4-byte Folded Spill
+; LA32-NEXT:    addi.w $fp, $sp, 16
+; LA32-NEXT:    ld.w $a0, $fp, -8
+; LA32-NEXT:    ld.w $a0, $a0, -8
+; LA32-NEXT:    ld.w $fp, $sp, 8 # 4-byte Folded Reload
+; LA32-NEXT:    ld.w $ra, $sp, 12 # 4-byte Folded Reload
+; LA32-NEXT:    addi.w $sp, $sp, 16
+; LA32-NEXT:    ret
+;
+; LA64-LABEL: test_frameaddress_2:
+; LA64:       # %bb.0:
+; LA64-NEXT:    addi.d $sp, $sp, -16
+; LA64-NEXT:    st.d $ra, $sp, 8 # 8-byte Folded Spill
+; LA64-NEXT:    st.d $fp, $sp, 0 # 8-byte Folded Spill
+; LA64-NEXT:    addi.d $fp, $sp, 16
+; LA64-NEXT:    ld.d $a0, $fp, -16
+; LA64-NEXT:    ld.d $a0, $a0, -16
+; LA64-NEXT:    ld.d $fp, $sp, 0 # 8-byte Folded Reload
+; LA64-NEXT:    ld.d $ra, $sp, 8 # 8-byte Folded Reload
+; LA64-NEXT:    addi.d $sp, $sp, 16
+; LA64-NEXT:    ret
+  %1 = call ptr @llvm.frameaddress(i32 2)
+  ret ptr %1
+}
+
 define ptr @test_returnaddress_0() nounwind {
 ; LA32-LABEL: test_returnaddress_0:
 ; LA32:       # %bb.0:
 ; LA32-NEXT:    move $a0, $ra
 ; LA32-NEXT:    ret
 ;
 ; LA64-LABEL: test_returnaddress_0:
 ; LA64:       # %bb.0:
 ; LA64-NEXT:    move $a0, $ra
 ; LA64-NEXT:    ret
   %1 = call ptr @llvm.returnaddress(i32 0)
   ret ptr %1
 }