div
Signed division
This instruction is defined by:
-
M, version >= 0
This instruction is included in the following profiles:
-
RVA20U64 (Mandatory)
-
RVA22U64 (Mandatory)
-
RVI20U32 (Optional)
-
RVI20U64 (Optional)
Synopsis
Divide rs1 by rs2, and store the result in rd. The remainder is discarded.
Division by zero will put -1 into rd.
Division resulting in signed overflow (when most negative number is divided by -1) will put the most negative number into rd;
Decode Variables
Bits<5> rs2 = $encoding[24:20];
Bits<5> rs1 = $encoding[19:15];
Bits<5> rd = $encoding[11:7];Execution
-
IDL
-
Sail
if (implemented?(ExtensionName::M) && (CSR[misa].M == 1'b0)) {
raise(ExceptionCode::IllegalInstruction, mode(), $encoding);
}
XReg src1 = X[rs1];
XReg src2 = X[rs2];
if (src2 == 0) {
X[rd] = {XLEN{1'b1}};
} else if ((src1 == {1'b1, {XLEN - 1{1'b0}}}) && (src2 == {XLEN{1'b1}})) {
X[rd] = {1'b1, {XLEN - 1{1'b0}}};
} else {
X[rd] = $signed(src1) / $signed(src2);
}{
if extension("M") then {
let rs1_val = X(rs1);
let rs2_val = X(rs2);
let rs1_int : int = if s then signed(rs1_val) else unsigned(rs1_val);
let rs2_int : int = if s then signed(rs2_val) else unsigned(rs2_val);
let q : int = if rs2_int == 0 then -1 else quot_round_zero(rs1_int, rs2_int);
/* check for signed overflow */
let q': int = if s & q > xlen_max_signed then xlen_min_signed else q;
X(rd) = to_bits(sizeof(xlen), q');
RETIRE_SUCCESS
} else {
handle_illegal();
RETIRE_FAIL
}
}