[RISCV] Set isTrap for EBREAK and {C_,}UNIMP (#131636)

This is done for completeness. The property isn't used in upstream
llvm/, although it is queried in BOLT in MCPlusBuilder.cpp.

Author: asb

llvm/lib/Target/RISCV/RISCVInstrInfo.td

@@ -752,6 +752,7 @@ def ECALL : RVInstI<0b000, OPC_SYSTEM, (outs), (ins), "ecall", "">, Sched<[Write
   let imm12 = 0;
 }
 
+let isTrap = 1 in
 def EBREAK : RVInstI<0b000, OPC_SYSTEM, (outs), (ins), "ebreak", "">,
              Sched<[]> {
   let rs1 = 0;
@@ -762,6 +763,7 @@ def EBREAK : RVInstI<0b000, OPC_SYSTEM, (outs), (ins), "ebreak", "">,
 // This is a de facto standard (as set by GNU binutils) 32-bit unimplemented
 // instruction (i.e., it should always trap, if your implementation has invalid
 // instruction traps).
+let isTrap = 1 in
 def UNIMP : RVInstI<0b001, OPC_SYSTEM, (outs), (ins), "unimp", "">,
             Sched<[]> {
   let rs1 = 0;

llvm/lib/Target/RISCV/RISCVInstrInfoC.td

@@ -596,7 +596,7 @@ def C_SDSP : CStackStore<0b111, "c.sdsp", GPR, uimm9_lsb000>,
 
 // The all zeros pattern isn't a valid RISC-V instruction. It's used by GNU
 // binutils as 16-bit instruction known to be unimplemented (i.e., trapping).
-let hasSideEffects = 1, mayLoad = 0, mayStore = 0 in
+let hasSideEffects = 1, mayLoad = 0, mayStore = 0, isTrap = 1 in
 def C_UNIMP : RVInst16<(outs), (ins), "c.unimp", "", [], InstFormatOther>,
               Sched<[]> {
   let Inst{15-0} = 0;