[RISCV] Prevent disassembling RVC hint instructions with x16-x31 for RVE. (#133805)

We can't ignore the return value form the GPR decode function, as it
contains the RVE check.

Author: topperc

llvm/lib/Target/RISCV/Disassembler/RISCVDisassembler.cpp

@@ -523,13 +523,13 @@ static DecodeStatus decodeCSSPushPopchk(MCInst &Inst, uint32_t Insn,
 static DecodeStatus decodeRVCInstrRdRs1ImmZero(MCInst &Inst, uint32_t Insn,
                                                uint64_t Address,
                                                const MCDisassembler *Decoder) {
+  DecodeStatus S = MCDisassembler::Success;
   uint32_t Rd = fieldFromInstruction(Insn, 7, 5);
-  [[maybe_unused]] DecodeStatus Result =
-      DecodeGPRNoX0RegisterClass(Inst, Rd, Address, Decoder);
-  assert(Result == MCDisassembler::Success && "Invalid register");
+  if (!Check(S, DecodeGPRNoX0RegisterClass(Inst, Rd, Address, Decoder)))
+    return MCDisassembler::Fail;
   Inst.addOperand(Inst.getOperand(0));
   Inst.addOperand(MCOperand::createImm(0));
-  return MCDisassembler::Success;
+  return S;
 }
 
 static DecodeStatus decodeCSSPushPopchk(MCInst &Inst, uint32_t Insn,
@@ -569,34 +569,44 @@ decodeRVCInstrRdRs1UImmLog2XLenNonZero(MCInst &Inst, uint32_t Insn,
 static DecodeStatus decodeRVCInstrRdRs2(MCInst &Inst, uint32_t Insn,
                                         uint64_t Address,
                                         const MCDisassembler *Decoder) {
+  DecodeStatus S = MCDisassembler::Success;
   uint32_t Rd = fieldFromInstruction(Insn, 7, 5);
   uint32_t Rs2 = fieldFromInstruction(Insn, 2, 5);
-  DecodeGPRRegisterClass(Inst, Rd, Address, Decoder);
-  DecodeGPRRegisterClass(Inst, Rs2, Address, Decoder);
-  return MCDisassembler::Success;
+  if (!Check(S, DecodeGPRRegisterClass(Inst, Rd, Address, Decoder)))
+    return MCDisassembler::Fail;
+  if (!Check(S, DecodeGPRRegisterClass(Inst, Rs2, Address, Decoder)))
+    return MCDisassembler::Fail;
+  return S;
 }
 
 static DecodeStatus decodeRVCInstrRdRs1Rs2(MCInst &Inst, uint32_t Insn,
                                            uint64_t Address,
                                            const MCDisassembler *Decoder) {
+  DecodeStatus S = MCDisassembler::Success;
   uint32_t Rd = fieldFromInstruction(Insn, 7, 5);
   uint32_t Rs2 = fieldFromInstruction(Insn, 2, 5);
-  DecodeGPRRegisterClass(Inst, Rd, Address, Decoder);
+  if (!Check(S, DecodeGPRRegisterClass(Inst, Rd, Address, Decoder)))
+    return MCDisassembler::Fail;
   Inst.addOperand(Inst.getOperand(0));
-  DecodeGPRRegisterClass(Inst, Rs2, Address, Decoder);
-  return MCDisassembler::Success;
+  if (!Check(S, DecodeGPRRegisterClass(Inst, Rs2, Address, Decoder)))
+    return MCDisassembler::Fail;
+  return S;
 }
 
 static DecodeStatus decodeXTHeadMemPair(MCInst &Inst, uint32_t Insn,
                                         uint64_t Address,
                                         const MCDisassembler *Decoder) {
+  DecodeStatus S = MCDisassembler::Success;
   uint32_t Rd1 = fieldFromInstruction(Insn, 7, 5);
   uint32_t Rs1 = fieldFromInstruction(Insn, 15, 5);
   uint32_t Rd2 = fieldFromInstruction(Insn, 20, 5);
   uint32_t UImm2 = fieldFromInstruction(Insn, 25, 2);
-  DecodeGPRRegisterClass(Inst, Rd1, Address, Decoder);
-  DecodeGPRRegisterClass(Inst, Rd2, Address, Decoder);
-  DecodeGPRRegisterClass(Inst, Rs1, Address, Decoder);
+  if (!Check(S, DecodeGPRRegisterClass(Inst, Rd1, Address, Decoder)))
+    return MCDisassembler::Fail;
+  if (!Check(S, DecodeGPRRegisterClass(Inst, Rd2, Address, Decoder)))
+    return MCDisassembler::Fail;
+  if (!Check(S, DecodeGPRRegisterClass(Inst, Rs1, Address, Decoder)))
+    return MCDisassembler::Fail;
   [[maybe_unused]] DecodeStatus Result =
       decodeUImmOperand<2>(Inst, UImm2, Address, Decoder);
   assert(Result == MCDisassembler::Success && "Invalid immediate");
@@ -610,7 +620,7 @@ static DecodeStatus decodeXTHeadMemPair(MCInst &Inst, uint32_t Insn,
   else
     Inst.addOperand(MCOperand::createImm(4));
 
-  return MCDisassembler::Success;
+  return S;
 }
 
 static DecodeStatus decodeZcmpRlist(MCInst &Inst, uint32_t Imm,

llvm/test/MC/RISCV/rve-invalid.s

@@ -1,16 +1,17 @@
-# RUN: not llvm-mc -triple riscv32 -mattr=+e < %s 2>&1 | FileCheck %s
-# RUN: llvm-mc -filetype=obj -triple=riscv32 < %s \
-# RUN:     | llvm-objdump --mattr=+e -M no-aliases -d -r - \
+# RUN: not llvm-mc -triple riscv32 -mattr=+e,+zca < %s 2>&1 | FileCheck %s
+# RUN: llvm-mc -filetype=obj -triple=riscv32 -mattr=+zca < %s \
+# RUN:     | llvm-objdump --mattr=+e,+zca -M no-aliases -d -r - \
 # RUN:     | FileCheck -check-prefix=CHECK-DIS %s
-# RUN: not llvm-mc -triple riscv64 -mattr=+e < %s 2>&1 | FileCheck %s
-# RUN: llvm-mc -filetype=obj -triple=riscv64 < %s \
-# RUN:     | llvm-objdump --mattr=+e -M no-aliases -d -r - \
+# RUN: not llvm-mc -triple riscv64 -mattr=+e,+zca < %s 2>&1 | FileCheck %s
+# RUN: llvm-mc -filetype=obj -triple=riscv64 -mattr=+zca < %s \
+# RUN:     | llvm-objdump --mattr=+e,+zca -M no-aliases -d -r - \
 # RUN:     | FileCheck -check-prefix=CHECK-DIS %s
 
 # Perform a simple check that registers x16-x31 (and the equivalent ABI names)
 # are rejected for RV32E/RV64E, when both assembling and disassembling.
 
-
+.option push
+.option exact
 # CHECK-DIS: 00001837 <unknown>
 # CHECK: :[[@LINE+1]]:5: error: invalid operand for instruction
 lui x16, 1
@@ -108,3 +109,14 @@ auipc t5, 31
 # CHECK-DIS: 00020f97 <unknown>
 # CHECK: :[[@LINE+1]]:7: error: invalid operand for instruction
 auipc t6, 32
+.option pop
+
+# CHECK-DIS: 0f81 <unknown>
+# CHECK: :[[@LINE+1]]:8: error: register must be a GPR excluding zero (x0)
+c.addi x31, 0
+# CHECK-DIS: 9846 <unknown>
+# CHECK: :[[@LINE+1]]:7: error: register must be a GPR excluding zero (x0)
+c.add x16, x17
+# CHECK-DIS: 8046 <unknown>
+# CHECK: :[[@LINE+1]]:10: error: register must be a GPR excluding zero (x0)
+c.mv x0, x17