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target/riscv/csr.c: fix 'ret' deadcode in rmw_xireg()

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Coverity found a second DEADCODE issue in rmw_xireg() claiming that we can't
reach 'RISCV_EXCP_NONE' at the 'done' label:

 > 2706     done:
 > 2707         if (ret) {
 > 2708             return (env->virt_enabled && virt) ?
 > 2709                    RISCV_EXCP_VIRT_INSTRUCTION_FAULT : RISCV_EXCP_ILLEGAL_INST;
 > 2710         }
 >>>>      CID 1590356:  Control flow issues  (DEADCODE)
 >>>>      Execution cannot reach this statement: "return RISCV_EXCP_NONE;".
 > 2711         return RISCV_EXCP_NONE;

Our label is now reduced after fixing another deadcode in the previous
patch but the problem reported here still remains:

 done:
    if (ret) {
        return RISCV_EXCP_ILLEGAL_INST;
    }
    return RISCV_EXCP_NONE;

This happens because 'ret' changes only once at the start of the
function:

    ret = smstateen_acc_ok(env, 0, SMSTATEEN0_SVSLCT);
    if (ret != RISCV_EXCP_NONE) {
        return ret;
    }

So it's a guarantee that ret will be RISCV_EXCP_NONE (-1) if we ever
reach the label, i.e. "if (ret)" will always be true, and  the label can
be even further reduced to:

done:
    return RISCV_EXCP_ILLEGAL_INST;

To make a better use of the label, remove the 'else' from the
xiselect_aia_range() chain and let it fall-through to the 'done' label
since they are now both returning RISCV_EXCP_ILLEGAL_INST.

Resolves: Coverity CID 1590356
Fixes: dc0280723d ("target/riscv: Decouple AIA processing from xiselect and xireg")
Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-ID: <20250121184847.2109128-3-dbarboza@ventanamicro.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
This commit is contained in:
Daniel Henrique Barboza 2025-01-21 15:48:44 -03:00 • committed by Alistair Francis
parent bf031e257d
commit e07a89143b
1 changed files with 1 additions and 6 deletions
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7
target/riscv/csr.c
View file

@ -2697,15 +2697,10 @@ static RISCVException rmw_xireg(CPURISCVState *env, int csrno,
} else if (riscv_cpu_cfg(env)->ext_smcsrind ||
riscv_cpu_cfg(env)->ext_sscsrind) {
return rmw_xireg_csrind(env, csrno, isel, val, new_val, wr_mask);
} else {
return RISCV_EXCP_ILLEGAL_INST;
}
done:
if (ret) {
return RISCV_EXCP_ILLEGAL_INST;
}
return RISCV_EXCP_NONE;
return RISCV_EXCP_ILLEGAL_INST;
}
static RISCVException rmw_xtopei(CPURISCVState *env, int csrno,