| Opcode/Instruction | Op/En | 64/32-bit Mode | CPUID Feature Flag | Description |
| 66 0F 38 DF /r AESDECLAST xmm1, xmm2/m128 | RM | V/V | AES | Perform the last round of an AES decryption flow, using the Equivalent Inverse Cipher, operating on a 128-bit data (state) from xmm1 with a 128-bit round key from xmm2/m128. |
| VEX.NDS.128.66.0F38.WIG DF /r VAESDECLAST xmm1, xmm2, xmm3/m128 | RVM | V/V | Both AES and AVX flags | Perform the last round of an AES decryption flow, using the Equivalent Inverse Cipher, operating on a 128-bit data (state) from xmm2 with a 128-bit round key from xmm3/m128; store the result in xmm1. |
| Op/En | Operand 1 | Operand2 | Operand3 | Operand4 |
| RM | ModRM:reg (r, w) | ModRM:r/m (r) | NA | NA |
| RVM | ModRM:reg (w) | VEX.vvvv (r) | ModRM:r/m (r) | NA |
This instruction performs the last round of the AES decryption flow using the Equivalent Inverse Cipher, with the round key from the second source operand, operating on a 128-bit data (state) from the first source operand, and store the result in the destination operand. 128-bit Legacy SSE version: The first source operand and the destination operand are the same and must be an XMM register. The second source operand can be an XMM register or a 128-bit memory location. Bits (VLMAX1:128) of the corresponding YMM destination register remain unchanged. VEX.128 encoded version: The first source operand and the destination operand are XMM registers. The second source operand can be an XMM register or a 128-bit memory location. Bits (VLMAX-1:128) of the destination YMM register are zeroed.
AESDECLAST STATE ← SRC1; RoundKey ← SRC2; STATE ← InvShiftRows( STATE ); STATE ← InvSubBytes( STATE ); DEST[127:0] ← STATE XOR RoundKey; DEST[VLMAX-1:128] (Unmodified) VAESDECLAST STATE ← SRC1; RoundKey ← SRC2; STATE ← InvShiftRows( STATE ); STATE ← InvSubBytes( STATE ); DEST[127:0] ← STATE XOR RoundKey; DEST[VLMAX-1:128] ← 0
| (V)AESDECLAST: | __m128i _mm_aesdeclast (__m128i, __m128i) |
None
See Exceptions Type 4.