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Source code

AESDEC

Perform One Round of an AES Decryption Flow

stableVMJITAOTinstruction

Encodings

OpcodeInstructionOp/En64-bitCompat/LegacyDescription
66 0F 38 DE /rAESDEC xmm1, xmm2/m128AValidValidPerform one round of an AES decryption flow, using the Equivalent Inverse Cipher, using one 128-bit data (state) from xmm1 with one 128-bit round key from xmm2/m128.
VEX.128.66.0F38.WIG DE /rVAESDEC xmm1, xmm2, xmm3/m128BValidValidPerform one round of an AES decryption flow, using AVX the Equivalent Inverse Cipher, using one 128-bit data (state) from xmm2 with one 128-bit round key from xmm3/m128; store the result in xmm1.
VEX.256.66.0F38.WIG DE /rVAESDEC ymm1, ymm2, ymm3/m256BValidValidPerform one round of an AES decryption flow, using the Equivalent Inverse Cipher, using two 128-bit data (state) from ymm2 with two 128-bit round keys from ymm3/m256; store the result in ymm1.
EVEX.128.66.0F38.WIG DE /rVAESDEC xmm1, xmm2, xmm3/m128CValidValidPerform one round of an AES decryption flow, using (AVX512VL OR AVX10.1) the Equivalent Inverse Cipher, using one 128-bit data (state) from xmm2 with one 128-bit round key from xmm3/m128; store the result in xmm1.
EVEX.256.66.0F38.WIG DE /rVAESDEC ymm1, ymm2, ymm3/m256CValidValidPerform one round of an AES decryption flow, using (AVX512VL OR AVX10.1) the Equivalent Inverse Cipher, using two 128-bit data (state) from ymm2 with two 128-bit round keys from ymm3/m256; store the result in ymm1.
EVEX.512.66.0F38.WIG DE /rVAESDEC zmm1, zmm2, zmm3/m512CValidValidPerform one round of an AES decryption flow, using (AVX512F OR AVX10.1) the Equivalent Inverse Cipher, using four 128-bit data (state) from zmm2 with four 128-bit round keys from zmm3/m512; store the result in zmm1.

Operand encoding

Each mode is a value of the Op/En column above. It says which field of the encoded instruction carries each operand, in the order they are written, and whether the instruction reads it, writes it or both.

A

  1. modrm.reg lectura y escrituraModRM byte, reg field (bits 5-3)
  2. modrm.rm lecturaModRM byte, r/m field (bits 2-0); with the SIB byte and the displacement when the mod field asks for them

B

  1. modrm.reg escrituraModRM byte, reg field (bits 5-3)
  2. vex.vvvv lecturaVEX prefix, vvvv field (inverted)
  3. modrm.rm lecturaModRM byte, r/m field (bits 2-0); with the SIB byte and the displacement when the mod field asks for them

C

  1. modrm.reg escrituraModRM byte, reg field (bits 5-3)
  2. evex.vvvv lecturaEVEX prefix, vvvv field (inverted)
  3. modrm.rm lecturaModRM byte, r/m field (bits 2-0); with the SIB byte and the displacement when the mod field asks for them

Tupla: Full Mem

Measured cost

Loading measurements from arch-data...

Description

This instruction performs a single round of the AES decryption flow using the Equivalent Inverse Cipher, using one/two/four (depending on vector length) 128-bit data (state) from the first source operand with one/two/four (depending on vector length) round key(s) from the second source operand, and stores the result in the destination operand.

Use the AESDEC instruction for all but the last decryption round. For the last decryption round, use the AESDE- CLAST instruction.

VEX and EVEX encoded versions of the instruction allow 3-operand (non-destructive) operation. The legacy encoded versions of the instruction require that the first source operand and the destination operand are the same and must be an XMM register.

The EVEX encoded form of this instruction does not support memory fault suppression.

Operation

AESDEC
STATE := SRC1;
RoundKey := SRC2;
STATE := InvShiftRows( STATE );
STATE := InvSubBytes( STATE );
STATE := InvMixColumns( STATE );
DEST[127:0] := STATE XOR RoundKey;
DEST[MAXVL-1:128] (Unmodified)

VAESDEC (128b and 256b VEX Encoded Versions)
(KL,VL) = (1,128), (2,256)
FOR i = 0 to KL-1:

    STATE := SRC1.xmm[i]
    RoundKey := SRC2.xmm[i]
    STATE := InvShiftRows( STATE )
    STATE := InvSubBytes( STATE )
    STATE := InvMixColumns( STATE )
    DEST.xmm[i] := STATE XOR RoundKey
DEST[MAXVL-1:VL] := 0

VAESDEC (EVEX Encoded Version)
(KL,VL) = (1,128), (2,256), (4,512)
FOR i = 0 to KL-1:

    STATE := SRC1.xmm[i]
    RoundKey := SRC2.xmm[i]
    STATE := InvShiftRows( STATE )
    STATE := InvSubBytes( STATE )
    STATE := InvMixColumns( STATE )
    DEST.xmm[i] := STATE XOR RoundKey
DEST[MAXVL-1:VL] :=0

Intel C/C++ compiler intrinsics

(V)AESDEC __m128i _mm_aesdec (__m128i, __m128i) VAESDEC __m256i _mm256_aesdec_epi128(__m256i, __m256i);
VAESDEC __m512i _mm512_aesdec_epi128(__m512i, __m512i);

SIMD Floating-Point Exceptions

None.

Other Exceptions

See Table 2-21, "Type 4 Class Exception Conditions."

EVEX-encoded: See Table 2-52, "Type E4NF Class Exception Conditions."

Sources