[ARM64EC 9/?] Implement CFGuard convention.

[efriedma]

Summary

Part of initial Arm64EC patchset.

CFG checkers on ARM64EC take two arguments: the callee, and an exit thunk to translate. The values are passed in x11 and x10. The function to call is then returned in x11.

[efriedma]

Rebased

llvm/lib/Target/AArch64/AArch64CallingConvention.h

bool CC_AArch64_DarwinPCS_ILP32_VarArg(unsigned ValNo, MVT ValVT, MVT LocVT,
                           CCValAssign::LocInfo LocInfo,
                           ISD::ArgFlagsTy ArgFlags, CCState &State);
 bool CC_AArch64_Win64_VarArg(unsigned ValNo, MVT ValVT, MVT LocVT,
                              CCValAssign::LocInfo LocInfo,
                              ISD::ArgFlagsTy ArgFlags, CCState &State);
 bool CC_AArch64_Win64_CFGuard_Check(unsigned ValNo, MVT ValVT, MVT LocVT,
                                     CCValAssign::LocInfo LocInfo,
                                     ISD::ArgFlagsTy ArgFlags, CCState &State);
+bool CC_AArch64_Arm64EC_CFGuard_Check(unsigned ValNo, MVT ValVT, MVT LocVT,
+                                      CCValAssign::LocInfo LocInfo,
+                                      ISD::ArgFlagsTy ArgFlags, CCState &State);
 bool CC_AArch64_WebKit_JS(unsigned ValNo, MVT ValVT, MVT LocVT,
                           CCValAssign::LocInfo LocInfo,
                           ISD::ArgFlagsTy ArgFlags, CCState &State);
 bool CC_AArch64_GHC(unsigned ValNo, MVT ValVT, MVT LocVT,
                     CCValAssign::LocInfo LocInfo, ISD::ArgFlagsTy ArgFlags,
                     CCState &State);
 bool RetCC_AArch64_AAPCS(unsigned ValNo, MVT ValVT, MVT LocVT,
                          CCValAssign::LocInfo LocInfo, ISD::ArgFlagsTy ArgFlags,
                          CCState &State);
 bool RetCC_AArch64_Arm64EC_Thunk(unsigned ValNo, MVT ValVT, MVT LocVT,
                                  CCValAssign::LocInfo LocInfo,
                                  ISD::ArgFlagsTy ArgFlags, CCState &State);
+bool RetCC_AArch64_Arm64EC_CFGuard_Check(unsigned ValNo, MVT ValVT, MVT LocVT,
+                                         CCValAssign::LocInfo LocInfo,
+                                         ISD::ArgFlagsTy ArgFlags,
+                                         CCState &State);
 bool RetCC_AArch64_WebKit_JS(unsigned ValNo, MVT ValVT, MVT LocVT,
                              CCValAssign::LocInfo LocInfo,
                              ISD::ArgFlagsTy ArgFlags, CCState &State);
 } // namespace llvm
 
 #endif

llvm/lib/Target/AArch64/AArch64CallingConvention.td

 
 // Windows Control Flow Guard checks take a single argument (the target function
 // address) and have no return value.
 let Entry = 1 in
 def CC_AArch64_Win64_CFGuard_Check : CallingConv<[
   CCIfType<[i64], CCAssignToReg<[X15]>>
 ]>;
 
+let Entry = 1 in
+def CC_AArch64_Arm64EC_CFGuard_Check : CallingConv<[
+  CCIfType<[i64], CCAssignToReg<[X11, X10]>>
+]>;
+
+let Entry = 1 in
+def RetCC_AArch64_Arm64EC_CFGuard_Check : CallingConv<[
+  CCIfType<[i64], CCAssignToReg<[X11]>>
+]>;
+
 
 // Darwin uses a calling convention which differs in only two ways
 // from the standard one at this level:
 //     + i128s (i.e. split i64s) don't need even registers.
 //     + Stack slots are sized as needed rather than being at least 64-bit.
 let Entry = 1 in
 def CC_AArch64_DarwinPCS : CallingConv<[
   CCIfType<[iPTR], CCBitConvertToType<i64>>,

llvm/lib/Target/AArch64/AArch64ISelLowering.cpp

CCAssignFn *AArch64TargetLowering::CCAssignFnForCall(CallingConv::ID CC,
   case CallingConv::Win64:
     if (IsVarArg) {
       if (Subtarget->isWindowsArm64EC())
         return CC_AArch64_Arm64EC_VarArg;
       return CC_AArch64_Win64_VarArg;
     }
     return CC_AArch64_AAPCS;
   case CallingConv::CFGuard_Check:
+    if (Subtarget->isWindowsArm64EC())
+      return CC_AArch64_Arm64EC_CFGuard_Check;
     return CC_AArch64_Win64_CFGuard_Check;
   case CallingConv::AArch64_VectorCall:
   case CallingConv::AArch64_SVE_VectorCall:
     return CC_AArch64_AAPCS;
   case CallingConv::ARM64EC_Thunk_X64:
     return CC_AArch64_Arm64EC_Thunk;
   case CallingConv::ARM64EC_Thunk_Native:
     return CC_AArch64_Arm64EC_Thunk_Native;
   }
 }
 
 CCAssignFn *
 AArch64TargetLowering::CCAssignFnForReturn(CallingConv::ID CC) const {
   switch (CC) {
   default:
     return RetCC_AArch64_AAPCS;
   case CallingConv::WebKit_JS:
     return RetCC_AArch64_WebKit_JS;
   case CallingConv::ARM64EC_Thunk_X64:
     return RetCC_AArch64_Arm64EC_Thunk;
+  case CallingConv::CFGuard_Check:
+    if (Subtarget->isWindowsArm64EC())
+      return RetCC_AArch64_Arm64EC_CFGuard_Check;
+    return RetCC_AArch64_AAPCS;
   }
 }
 
 SDValue AArch64TargetLowering::LowerFormalArguments(
     SDValue Chain, CallingConv::ID CallConv, bool isVarArg,
     const SmallVectorImpl<ISD::InputArg> &Ins, const SDLoc &DL,
     SelectionDAG &DAG, SmallVectorImpl<SDValue> &InVals) const {
   MachineFunction &MF = DAG.getMachineFunction();