# BNDCL — Check Lower Bound

Opcode/Instruction | Op/En | 64/32 bit Mode Support | CPUID Feature Flag | Description
--- | --- | --- | --- | ---
F3 0F 1A /r BNDCL bnd, r/m32 | RM | N.E./V | MPX | Generate a #BR if the address in r/m32 is lower than the lower bound in bnd.LB.
F3 0F 1A /r BNDCL bnd, r/m64 | RM | V/N.E. | MPX | Generate a #BR if the address in r/m64 is lower than the lower bound in bnd.LB.

## Instruction Operand Encoding ¶

Op/En | Operand 1 | Operand 2 | Operand 3
--- | --- | --- | ---
RM | ModRM:reg (w) | ModRM:r/m (r) | N/A

## Description ¶

Compare the address in the second operand with the lower bound in bnd. The second operand can be either a register or memory operand. If the address is lower than the lower bound in bnd.LB, it will set BNDSTATUS to 01H and signal a #BR exception.

This instruction does not cause any memory access, and does not read or write any flags.

## Operation ¶

### BNDCL BND, reg ¶

    IF reg < BND.LB Then
        BNDSTATUS := 01H;
        #BR;
    FI;

### BNDCL BND, mem ¶

    TEMP := LEA(mem);
    IF TEMP < BND.LB Then
        BNDSTATUS := 01H;
        #BR;
    FI;

## Intel C/C++ Compiler Intrinsic Equivalent ¶

    BNDCL void _bnd_chk_ptr_lbounds(const void *q)

## Flags Affected ¶

None

## Protected Mode Exceptions ¶

#BR | If lower bound check fails.
#UD | If the LOCK prefix is used.
If ModRM.r/m encodes BND4-BND7 when Intel MPX is enabled.
If 67H prefix is not used and CS.D=0.
If 67H prefix is used and CS.D=1.

## Real-Address Mode Exceptions ¶

#BR | If lower bound check fails.
#UD | If the LOCK prefix is used.
If ModRM.r/m encodes BND4-BND7 when Intel MPX is enabled.
If 16-bit addressing is used.

## Virtual-8086 Mode Exceptions ¶

#BR | If lower bound check fails.
#UD | If the LOCK prefix is used.
If ModRM.r/m encodes BND4-BND7 when Intel MPX is enabled.
If 16-bit addressing is used.

## Compatibility Mode Exceptions ¶

Same exceptions as in protected mode.

## 64-Bit Mode Exceptions ¶

#UD | If ModRM.r/m and REX encodes BND4-BND15 when Intel MPX is enabled.

Same exceptions as in protected mode.