[RISCV] Add MC layer support for Zicfiss. (#66043)

The patch adds the instructions in Zicfiss extension. Zicfiss extension
is to support shadow stack for control flow integrity. This patch is
based on version [0.3.1].

[0.3.1]: https://github.com/riscv/riscv-cfi/releases/tag/v0.3.1

7 files changed, 133 insertions, 10 deletions

diff --git a/llvm/lib/Target/RISCV/Disassembler/RISCVDisassembler.cpp b/llvm/lib/Target/RISCV/Disassembler/RISCVDisassembler.cpp
index a639634..ed80da1 100644
--- a/llvm/lib/Target/RISCV/Disassembler/RISCVDisassembler.cpp
+++ b/llvm/lib/Target/RISCV/Disassembler/RISCVDisassembler.cpp
@@ -74,6 +74,17 @@ static DecodeStatus DecodeGPRRegisterClass(MCInst &Inst, uint32_t RegNo,
   return MCDisassembler::Success;
 }
 
+static DecodeStatus DecodeGPRX1X5RegisterClass(MCInst &Inst, uint32_t RegNo,
+                                               uint64_t Address,
+                                               const MCDisassembler *Decoder) {
+  MCRegister Reg = RISCV::X0 + RegNo;
+  if (Reg != RISCV::X1 && Reg != RISCV::X5)
+    return MCDisassembler::Fail;
+
+  Inst.addOperand(MCOperand::createReg(Reg));
+  return MCDisassembler::Success;
+}
+
 static DecodeStatus DecodeFPR16RegisterClass(MCInst &Inst, uint32_t RegNo,
                                              uint64_t Address,
                                              const MCDisassembler *Decoder) {
@@ -359,6 +370,10 @@ static DecodeStatus decodeRegReg(MCInst &Inst, uint32_t Insn, uint64_t Address,
 static DecodeStatus decodeZcmpSpimm(MCInst &Inst, unsigned Imm,
                                     uint64_t Address, const void *Decoder);
 
+static DecodeStatus decodeCSSPushPopchk(MCInst &Inst, uint32_t Insn,
+                                        uint64_t Address,
+                                        const MCDisassembler *Decoder);
+
 #include "RISCVGenDisassemblerTables.inc"
 
 static DecodeStatus decodeRVCInstrRdRs1ImmZero(MCInst &Inst, uint32_t Insn,
@@ -373,6 +388,16 @@ static DecodeStatus decodeRVCInstrRdRs1ImmZero(MCInst &Inst, uint32_t Insn,
   return MCDisassembler::Success;
 }
 
+static DecodeStatus decodeCSSPushPopchk(MCInst &Inst, uint32_t Insn,
+                                        uint64_t Address,
+                                        const MCDisassembler *Decoder) {
+  uint32_t Rs1 = fieldFromInstruction(Insn, 7, 5);
+  DecodeStatus Result = DecodeGPRX1X5RegisterClass(Inst, Rs1, Address, Decoder);
+  (void)Result;
+  assert(Result == MCDisassembler::Success && "Invalid register");
+  return MCDisassembler::Success;
+}
+
 static DecodeStatus decodeRVCInstrRdSImm(MCInst &Inst, uint32_t Insn,
                                          uint64_t Address,
                                          const MCDisassembler *Decoder) {
@@ -596,6 +621,8 @@ DecodeStatus RISCVDisassembler::getInstruction(MCInst &MI, uint64_t &Size,
   TRY_TO_DECODE_AND_ADD_SP(!STI.hasFeature(RISCV::Feature64Bit),
                            DecoderTableRISCV32Only_16,
                            "RISCV32Only_16 table (16-bit Instruction)");
+  TRY_TO_DECODE_FEATURE(RISCV::FeatureStdExtZicfiss, DecoderTableZicfiss16,
+                        "RVZicfiss table (Shadow Stack)");
   TRY_TO_DECODE_FEATURE(RISCV::FeatureStdExtZcmt, DecoderTableRVZcmt16,
                         "Zcmt table (16-bit Table Jump Instructions)");
   TRY_TO_DECODE_FEATURE(
diff --git a/llvm/lib/Target/RISCV/RISCVFeatures.td b/llvm/lib/Target/RISCV/RISCVFeatures.td
index bdab052..59b2026 100644
--- a/llvm/lib/Target/RISCV/RISCVFeatures.td
+++ b/llvm/lib/Target/RISCV/RISCVFeatures.td
@@ -700,6 +700,15 @@ def HasStdExtZcmop : Predicate<"Subtarget->hasStdExtZcmop()">,
                                AssemblerPredicate<(all_of FeatureStdExtZcmop),
                                "'Zcmop' (Compressed May-Be-Operations)">;
 
+def FeatureStdExtZicfiss
+    : SubtargetFeature<"experimental-zicfiss", "HasStdExtZicfiss", "true",
+                       "'Zicfiss' (Shadow stack)",
+                       [FeatureStdExtZicsr, FeatureStdExtZimop]>;
+def HasStdExtZicfiss : Predicate<"Subtarget->hasStdExtZicfiss()">,
+                                 AssemblerPredicate<(all_of FeatureStdExtZicfiss),
+                                 "'Zicfiss' (Shadow stack)">;
+def NoHasStdExtZicfiss : Predicate<"!Subtarget->hasStdExtZicfiss()">;
+
 def FeatureStdExtSmaia
     : SubtargetFeature<"smaia", "HasStdExtSmaia", "true",
                        "'Smaia' (Smaia encompasses all added CSRs and all "
diff --git a/llvm/lib/Target/RISCV/RISCVInstrInfo.td b/llvm/lib/Target/RISCV/RISCVInstrInfo.td
index b00cb26..35e8edf 100644
--- a/llvm/lib/Target/RISCV/RISCVInstrInfo.td
+++ b/llvm/lib/Target/RISCV/RISCVInstrInfo.td
@@ -2111,16 +2111,17 @@ include "RISCVInstrInfoZk.td"
 include "RISCVInstrInfoV.td"
 include "RISCVInstrInfoZvk.td"
 
-// Integer
-include "RISCVInstrInfoZimop.td"
-include "RISCVInstrInfoZicbo.td"
-include "RISCVInstrInfoZicond.td"
-
 // Compressed
 include "RISCVInstrInfoC.td"
 include "RISCVInstrInfoZc.td"
 include "RISCVInstrInfoZcmop.td"
 
+// Integer
+include "RISCVInstrInfoZimop.td"
+include "RISCVInstrInfoZicbo.td"
+include "RISCVInstrInfoZicond.td"
+include "RISCVInstrInfoZicfiss.td"
+
 //===----------------------------------------------------------------------===//
 // Vendor extensions
 //===----------------------------------------------------------------------===//
diff --git a/llvm/lib/Target/RISCV/RISCVInstrInfoZcmop.td b/llvm/lib/Target/RISCV/RISCVInstrInfoZcmop.td
index 9213b20..6fbfde5 100644
--- a/llvm/lib/Target/RISCV/RISCVInstrInfoZcmop.td
+++ b/llvm/lib/Target/RISCV/RISCVInstrInfoZcmop.td
@@ -22,9 +22,13 @@ class CMOPInst<bits<3> imm3, string opcodestr>
   let Inst{12-11} = 0;
 }
 
-foreach i = 0...7 in {
-  let Predicates = [HasStdExtZcmop] in {
-    defvar n = !add(!mul(i, 2), 1);
-    def CMOP # n : CMOPInst<i, "cmop." # n>, Sched<[]>;
-  } // Predicates = [HasStdExtZcmop]
+// CMOP1, CMOP5 is used by Zicfiss.
+let Predicates = [HasStdExtZcmop, NoHasStdExtZicfiss] in {
+  def CMOP1 : CMOPInst<0, "cmop.1">, Sched<[]>;
+  def CMOP5 : CMOPInst<2, "cmop.5">, Sched<[]>;
+}
+
+foreach n = [3, 7, 9, 11, 13, 15] in {
+  let Predicates = [HasStdExtZcmop] in
+  def CMOP # n : CMOPInst<!srl(n, 1), "cmop." # n>, Sched<[]>;
 }
diff --git a/llvm/lib/Target/RISCV/RISCVInstrInfoZicfiss.td b/llvm/lib/Target/RISCV/RISCVInstrInfoZicfiss.td
new file mode 100644
index 0000000..49a57f8
--- /dev/null
+++ b/llvm/lib/Target/RISCV/RISCVInstrInfoZicfiss.td
@@ -0,0 +1,72 @@
+//===------ RISCVInstrInfoZicfiss.td - RISC-V Zicfiss -*- tablegen -*------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+//===----------------------------------------------------------------------===//
+// Instruction class templates
+//===----------------------------------------------------------------------===//
+
+class RVC_SSInst<bits<5> rs1val, RegisterClass reg_class, string opcodestr> :
+  RVInst16<(outs), (ins reg_class:$rs1), opcodestr, "$rs1", [], InstFormatOther> {
+  let Inst{15-13} = 0b011;
+  let Inst{12} = 0;
+  let Inst{11-7} = rs1val;
+  let Inst{6-2} = 0b00000;
+  let Inst{1-0} = 0b01;
+  let DecoderMethod = "decodeCSSPushPopchk";
+}
+
+//===----------------------------------------------------------------------===//
+// Instructions
+//===----------------------------------------------------------------------===//
+
+let Predicates = [HasStdExtZicfiss] in {
+let Uses = [SSP], Defs = [SSP], hasSideEffects = 0, mayLoad = 1, mayStore = 0 in
+def SSPOPCHK : RVInstI<0b100, OPC_SYSTEM, (outs), (ins GPRX1X5:$rs1), "sspopchk",
+                       "$rs1"> {
+  let rd = 0;
+  let imm12 = 0b110011011100;
+} // Uses = [SSP],  Defs = [SSP], hasSideEffects = 0, mayLoad = 1, mayStore = 0
+
+let Uses = [SSP], hasSideEffects = 0, mayLoad = 0, mayStore = 0 in {
+def SSRDP : RVInstI<0b100, OPC_SYSTEM, (outs GPRNoX0:$rd), (ins), "ssrdp", "$rd"> {
+  let imm12 = 0b110011011100;
+  let rs1 = 0b00000;
+}
+} // Uses = [SSP], hasSideEffects = 0, mayLoad = 0, mayStore = 0
+
+let Uses = [SSP], Defs = [SSP], hasSideEffects = 0, mayLoad = 0, mayStore = 1 in
+def SSPUSH : RVInstR<0b1100111, 0b100, OPC_SYSTEM, (outs), (ins GPRX1X5:$rs2),
+                     "sspush", "$rs2"> {
+  let rd = 0b00000;
+  let rs1 = 0b00000;
+}
+} // Predicates = [HasStdExtZicfiss]
+
+let Predicates = [HasStdExtZicfiss, HasStdExtZcmop],
+    DecoderNamespace = "Zicfiss" in {
+let Uses = [SSP], Defs = [SSP], hasSideEffects = 0, mayLoad = 0, mayStore = 1 in
+def C_SSPUSH : RVC_SSInst<0b00001, GPRX1, "c.sspush">;
+
+let Uses = [SSP], Defs = [SSP], hasSideEffects = 0, mayLoad = 1, mayStore = 0 in
+def C_SSPOPCHK : RVC_SSInst<0b00101, GPRX5, "c.sspopchk">;
+} // Predicates = [HasStdExtZicfiss, HasStdExtZcmop]
+
+let Predicates = [HasStdExtZicfiss] in
+defm SSAMOSWAP_W  : AMO_rr_aq_rl<0b01001, 0b010, "ssamoswap.w">;
+
+let Predicates = [HasStdExtZicfiss, IsRV64] in
+defm SSAMOSWAP_D  : AMO_rr_aq_rl<0b01001, 0b011, "ssamoswap.d">;
+
+//===----------------------------------------------------------------------===/
+// Compress Instruction tablegen backend.
+//===----------------------------------------------------------------------===//
+
+let Predicates = [HasStdExtZicfiss, HasStdExtZcmop] in {
+def : CompressPat<(SSPUSH X1), (C_SSPUSH X1)>;
+def : CompressPat<(SSPOPCHK X5), (C_SSPOPCHK X5)>;
+} // Predicates = [HasStdExtZicfiss, HasStdExtZcmop]
diff --git a/llvm/lib/Target/RISCV/RISCVRegisterInfo.cpp b/llvm/lib/Target/RISCV/RISCVRegisterInfo.cpp
index a3c1911..24f8d60 100644
--- a/llvm/lib/Target/RISCV/RISCVRegisterInfo.cpp
+++ b/llvm/lib/Target/RISCV/RISCVRegisterInfo.cpp
@@ -127,6 +127,9 @@ BitVector RISCVRegisterInfo::getReservedRegs(const MachineFunction &MF) const {
     markSuperRegs(Reserved, RISCV::X27);
   }
 
+  // Shadow stack pointer.
+  markSuperRegs(Reserved, RISCV::SSP);
+
   assert(checkAllSuperRegsMarked(Reserved));
   return Reserved;
 }
diff --git a/llvm/lib/Target/RISCV/RISCVRegisterInfo.td b/llvm/lib/Target/RISCV/RISCVRegisterInfo.td
index c59c9b2..840fd149 100644
--- a/llvm/lib/Target/RISCV/RISCVRegisterInfo.td
+++ b/llvm/lib/Target/RISCV/RISCVRegisterInfo.td
@@ -137,6 +137,8 @@ def GPR : GPRRegisterClass<(add (sequence "X%u", 10, 17),
                                 (sequence "X%u", 0, 4))>;
 
 def GPRX0 : GPRRegisterClass<(add X0)>;
+def GPRX1 : GPRRegisterClass<(add X1)>;
+def GPRX5 : GPRRegisterClass<(add X5)>;
 
 def GPRNoX0 : GPRRegisterClass<(sub GPR, X0)>;
 
@@ -165,6 +167,8 @@ def SP : GPRRegisterClass<(add X2)>;
 def SR07 : GPRRegisterClass<(add (sequence "X%u", 8, 9),
                                  (sequence "X%u", 18, 23))>;
 
+def GPRX1X5 :  GPRRegisterClass<(add X1, X5)>;
+
 // Floating point registers
 let RegAltNameIndices = [ABIRegAltName] in {
   def F0_H  : RISCVReg16<0, "f0", ["ft0"]>, DwarfRegNum<[32]>;
@@ -591,3 +595,6 @@ foreach m = LMULList in {
 // Special registers
 def FFLAGS : RISCVReg<0, "fflags">;
 def FRM    : RISCVReg<0, "frm">;
+
+// Shadow Stack register
+def SSP    : RISCVReg<0, "ssp">;