bexti

Single-Bit extract (Immediate)

This instruction is defined by:

Encoding

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Synopsis

Returns a single bit extracted from xs1 at the index specified in xs2. The index is read from the lower log2(XLEN) bits of shamt. For RV32, the encodings corresponding to shamt[5]=1 are reserved.

Access

M HS U VS VU

Always

Always

Always

Always

Always

Decode Variables

Bits<6> shamt = $encoding[25:20];
Bits<5> xs1 = $encoding[19:15];
Bits<5> xd = $encoding[11:7];

Execution

  • Pruned, XLEN == 64

  • Original

XReg index = shamt;
X[xd] = (X[xs1] >> index) & 1;
if (implemented?(ExtensionName::B) && (CSR[misa].B == 1'b0)) {
  raise(ExceptionCode::IllegalInstruction, mode(), $encoding);
}
XReg index = shamt & (xlen() - 1);
X[xd] = (X[xs1] >> index) & 1;