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.

Instruction Operand Encoding ¶

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.