gmi

Get Memory Tag Intersection

GMI <Xd>, <Xn|SP>, <Xm>

Calculates a mask of excluded tags (MTE).

Pseudocode Operation

ptr_tag ← (Xn >> 56) & 0xF
exclude_mask ← Xm & 0xFFFF
valid_tags ← ~exclude_mask & 0xFFFF
// Return mask of tags that are both valid (not excluded) and different from current tag
Xd ← valid_tags & ~(1 << ptr_tag)

Example

GMI x0, x1, x2

Encoding

Binary Layout

11010110

28:21

20:16

000101

15:10

9:5

4:0

Format Data Processing

Opcode 0x9AC01400

Extension MTE (Memory Tagging)

Operands

Xd
Dest Mask
Xn
Ptr
Xm
Excluded

Reference

View in Arm A64 ISA Reference ↗ Arm A64 ISA

Instruction Forms

Encoding	Instruction		ISA		Bit pattern
0x9AC01400	GMI <Xd>, <Xn\|SP>, <Xm>		A64		1 \| 0 \| 0 \| 11010110 \| Xm \| 000101 \| Xn \| Xd

Description

Tag Mask Insert inserts the tag in the first source register into the excluded set specified in the second source register, writing the new excluded set to the destination register.

Operation

bits(64) address = if n == 31 then SP[] else X[n, 64];
bits(64) mask = X[m, 64];
bits(4) tag = AArch64.AllocationTagFromAddress(address);

mask<UInt(tag)> = '1';
X[d, 64] = mask;

gmi