BNDCL

BNDCL

Intel Architecture Software Developer's Manual (July 2017)

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	NE/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/NE	MPX	Generate a #BR if the address in r/m64 is lower than the lower bound in bnd.LB.

Op/En	Operand 1	Operand 2	Operand 3
RM	ModRM:reg (w)	ModRM:r/m (r)	NA

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.