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decoder.sv: fix sfence.vma when rs1 != 0 (#933)

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unlike other instructions with minor opcode == PRIV,
SFENCE.VMA do not check for rs1 != 0.
Only check for rd !=0 to raise illegal instruction

Signed-off-by: Guillaume Chauvon <guillaume.chauvon@thalesgroup.com>
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Guillaume Chauvon 2022-07-20 17:03:06 +02:00 • committed by GitHub
parent 56ccf8089e
commit b6c1d04b6f
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core/decoder.sv
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@ -158,7 +158,7 @@ module decoder import ariane_pkg::*; (
if (instr.instr[31:25] == 7'b1001) begin
// check privilege level, SFENCE.VMA can only be executed in M/S mode
// otherwise decode an illegal instruction
illegal_instr = (priv_lvl_i inside {riscv::PRIV_LVL_M, riscv::PRIV_LVL_S}) ? illegal_instr : 1'b1;
illegal_instr = ((priv_lvl_i inside {riscv::PRIV_LVL_M, riscv::PRIV_LVL_S}) && instr.itype.rd == '0) ? 1'b0 : 1'b1;
instruction_o.op = ariane_pkg::SFENCE_VMA;
// check TVM flag and intercept SFENCE.VMA call if necessary
if (priv_lvl_i == riscv::PRIV_LVL_S && tvm_i)