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lib/crypto: x86/aes-ctr: Remove some unreachable code

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In the AES-CTR and AES-XCTR code that handles a remainder of '4*VL < LEN
< 8*VL', first 4 full vectors are processed, leaving 0 < LEN < 4*VL.
After that, five different cases are handled depending on whether there
are 0, 1, 2, 3, or 4 full vectors remaining.  But the case of 4 vectors
is never reached there, making the code handling it unused.  Remove it.

With that done, the '.Lxor_tail_partial_vec_3\@' block would be reached
only via an unconditional jump.  Therefore, relocate it to the only
place that jumps to it.  This allows removing the jump at the end of the
'.Lxor_tail_partial_vec_2\@' block and making it fall through.

Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://patch.msgid.link/20261002034405.49886-1-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
This commit is contained in:
Eric Biggers 2026-10-01 20:44:05 -07:00
parent 9ca77aa621
commit da4d5933e3
1 changed files with 6 additions and 12 deletions
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18
lib/crypto/x86/aes-ctr-avx-x86_64.S
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@ -419,10 +419,12 @@
cmp $3*VL-1, LEN32
jle .Lxor_tail_partial_vec_2\@
_xor_data 2
cmp $4*VL-1, LEN32
jle .Lxor_tail_partial_vec_3\@
_xor_data 3
jmp .Ldone\@
add $-3*VL, LEN32
jz .Ldone\@
sub $-3*VL, SRC
sub $-3*VL, DST
_vmovdqa AESDATA3, AESDATA0
jmp .Lxor_tail_partial_vec_0\@
.Lenc_tail_atmost4vecs\@:
cmp $2*VL, LEN32
@ -469,14 +471,6 @@
sub $-2*VL, SRC
sub $-2*VL, DST
_vmovdqa AESDATA2, AESDATA0
jmp .Lxor_tail_partial_vec_0\@
.Lxor_tail_partial_vec_3\@:
add $-3*VL, LEN32
jz .Ldone\@
sub $-3*VL, SRC
sub $-3*VL, DST
_vmovdqa AESDATA3, AESDATA0
.Lxor_tail_partial_vec_0\@:
// XOR the remaining 1 <= LEN < VL bytes. It's easy if masked