mul
Signed multiply
This instruction is defined by:
Synopsis
MUL performs an XLEN-bitxXLEN-bit multiplication of xs1 by xs2 and places the lower
XLEN bits in the destination register.
Any overflow is thrown away.
| If both the high and low bits of the same product are required, then the recommended code sequence is: MULH[[S]U] xdh, xs1, xs2; MUL xdl, xs1, xs2 (source register specifiers must be in same order and xdh cannot be the same as xs1 or xs2). Microarchitectures can then fuse these into a single multiply operation instead of performing two separate multiplies. |
Decode Variables
Bits<5> xs2 = $encoding[24:20];
Bits<5> xs1 = $encoding[19:15];
Bits<5> xd = $encoding[11:7];Execution
-
Pruned, XLEN == 64
-
Original
if (implemented?(ExtensionName::M) && (misa.M == 1'b0)) {
raise(ExceptionCode::IllegalInstruction, mode(), $encoding);
}
XReg src1 = X[xs1];
XReg src2 = X[xs2];
X[xd] = (src1 * src2)[63:0];if (implemented?(ExtensionName::M) && (misa.M == 1'b0)) {
raise(ExceptionCode::IllegalInstruction, mode(), $encoding);
}
XReg src1 = X[xs1];
XReg src2 = X[xs2];
X[xd] = (src1 * src2)[MXLEN - 1:0];