The LdaSmi bytecode in the V8 interpreter (it also checks if the next bytecode is store-a-on-stack and does that).

interpreter.txt

 1958cc0:       43 0f be 5c 0c 01       movsbl 0x1(%r12,%r9,1),%ebx       // ebx = load small int
 1958cc6:       49 8d 51 02             lea    0x2(%r9),%rdx              // rdx = next bytecode addr
 1958cca:       43 0f b6 74 0c 02       movzbl 0x2(%r12,%r9,1),%esi       // esi = peek at next bytecode
 1958cd0:       8d 04 1b                lea    (%rbx,%rbx,1),%eax         // eax = rbx * 2 (tag smi)
 1958cd3:       40 80 fe c1             cmp    $0xc1,%sil                 // is next bc star?  (Store accumulator in 'register'.
 1958cd7:       73 09                   jae    1958ce2 <Builtins_LdaSmiHandler+0x22>  // jmp if star
 1958cd9:       49 8b 0c f7             mov    (%r15,%rsi,8),%rcx         // add bytecode to r15, load next bytecode handler.
 1958cdd:       4c 8b ca                mov    %rdx,%r9                   // Update bytecode program counter
 1958ce0:       ff e1                   jmp    *%rcx                      // Dispatch to next handler
 1958ce2:       48 8b dd                mov    %rbp,%rbx                  // rbx = frame pointer
 1958ce5:       48 89 84 f3 48 f9 ff    mov    %rax,-0x6b8(%rbx,%rsi,8)   // store accumulator on stack (why not use rbp?)
 1958cec:       ff 
 1958ced:       48 8d 5a 01             lea    0x1(%rdx),%rbx             // rbx = next bytecode addr
 1958cf1:       43 0f b6 54 0c 03       movzbl 0x3(%r12,%r9,1),%edx       // load next bytecode to ecx
 1958cf7:       49 8b 0c d7             mov    (%r15,%rdx,8),%rcx         // add bytecode to r15, load next bytecode handler
 1958cfb:       4c 8b cb                mov    %rbx,%r9                   // update bytecode program counter
 1958cfe:       ff e1                   jmp    *%rcx                      // Dispatch to next handler
 1958d00:       90                      nop
 1958d01:       0f 1f 00                nopl   (%rax)