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Improve the overflow handling in rsaz_512_sqr

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We have always a carry in %rcx or %rbx in range 0..2
from the previous stage, that is added to the result
of the 64-bit square, but the low nibble of any square
can only be 0, 1, 4, 9.

Therefore one "adcq $0, %rdx" can be removed.
Likewise in the ADX code we can remove one
"adcx %rbp, $out" since %rbp is always 0, and carry is
also zero, therefore that is a no-op.

Reviewed-by: Paul Dale <paul.dale@oracle.com>
(Merged from https://github.com/openssl/openssl/pull/10575)
This commit is contained in:
Bernd Edlinger 2019-12-04 12:57:41 +01:00
parent 419102400a
commit 46ac489a13
1 changed files with 21 additions and 21 deletions
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42
crypto/bn/asm/rsaz-x86_64.pl
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@ -242,9 +242,9 @@ $code.=<<___;
adcq \$0, %rbx
mulq %rax
# rcx <= 2 and rax <= 0xFFFF..F9, so carry must be zero here
addq %rcx, %rax
movq 16($inp), %rbp
adcq \$0, %rdx
addq %rax, %r9
movq 24($inp), %rax
adcq %rdx, %r10
@ -298,9 +298,9 @@ $code.=<<___;
adcq \$0, %rcx
mulq %rax
# rbx <= 2 and rax <= 0xFFFF..F9, so carry must be zero here
addq %rbx, %rax
movq 24($inp), %r10
adcq \$0, %rdx
addq %rax, %r11
movq 32($inp), %rax
adcq %rdx, %r12
@ -349,8 +349,8 @@ $code.=<<___;
adcq \$0, %rbx
mulq %rax
# rcx <= 2 and rax <= 0xFFFF..F9, so carry must be zero here
addq %rcx, %rax
adcq \$0, %rdx
addq %rax, %r13
movq %r12, %rax # 40($inp)
adcq %rdx, %r14
@ -389,8 +389,8 @@ $code.=<<___;
adcq \$0, %rcx
mulq %rax
# rbx <= 2 and rax <= 0xFFFF..F9, so carry must be zero here
addq %rbx, %rax
adcq \$0, %rdx
addq %rax, %r15
movq %rbp, %rax # 48($inp)
adcq %rdx, %r8
@ -420,8 +420,8 @@ $code.=<<___;
adcq \$0, %rbx
mulq %rax
# rcx <= 2 and rax <= 0xFFFF..F9, so carry must be zero here
addq %rcx, %rax
adcq \$0, %rdx
addq %rax, %r9
movq %r14, %rax # 56($inp)
adcq %rdx, %r10
@ -443,8 +443,8 @@ $code.=<<___;
adcq \$0, %rcx
mulq %rax
# rbx <= 2 and rax <= 0xFFFF..F9, so carry must be zero here
addq %rbx, %rax
adcq \$0, %rdx
addq %rax, %r11
movq %r14, %rax # 56($inp)
adcq %rdx, %r12
@ -459,8 +459,8 @@ $code.=<<___;
adcq \$0, %rbx
mulq %rax
# rcx <= 2 and rax <= 0xFFFF..F9, so carry must be zero here
addq %rcx, %rax
adcq \$0, %rdx
addq %r13, %rax
adcq %rbx, %rdx
@ -572,9 +572,9 @@ $code.=<<___;
.byte 0x48,0x8b,0x96,0x10,0x00,0x00,0x00 # mov 16($inp), %rdx
xor %rbx, %rbx
adox %r9, %r9
# rcx <= 2 and rax <= 0xFFFF..F9, so carry must be zero here
adcx %rcx, %rax
adox %r9, %r9
adcx %rbp, $out
adox %r10, %r10
adcx %rax, %r9
adox %rbp, %rbx
@ -609,9 +609,9 @@ $code.=<<___;
mov 24($inp), %rdx
xor %rcx, %rcx
adox %r11, %r11
# rbx <= 2 and rax <= 0xFFFF..F9, so carry must be zero here
adcx %rbx, %rax
adox %r11, %r11
adcx %rbp, $out
adox %r12, %r12
adcx %rax, %r11
adox %rbp, %rcx
@ -642,9 +642,9 @@ $code.=<<___;
mov 32($inp), %rdx
xor %rbx, %rbx
adox %r13, %r13
# rcx <= 2 and rax <= 0xFFFF..F9, so carry must be zero here
adcx %rcx, %rax
adox %r13, %r13
adcx %rbp, $out
adox %r14, %r14
adcx %rax, %r13
adox %rbp, %rbx
@ -671,9 +671,9 @@ $code.=<<___;
adox %rbp, %r11
xor %rcx, %rcx
adox %r15, %r15
# rbx <= 2 and rax <= 0xFFFF..F9, so carry must be zero here
adcx %rbx, %rax
adox %r15, %r15
adcx %rbp, $out
adox %r8, %r8
adcx %rax, %r15
adox %rbp, %rcx
@ -696,9 +696,9 @@ $code.=<<___;
mov 48($inp), %rdx
xor %rbx, %rbx
adox %r9, %r9
# rcx <= 2 and rax <= 0xFFFF..F9, so carry must be zero here
adcx %rcx, %rax
adox %r9, %r9
adcx %rbp, $out
adox %r10, %r10
adcx %rax, %r9
adcx $out, %r10
@ -716,9 +716,9 @@ $code.=<<___;
mulx %rdx, %rax, $out
xor %rcx, %rcx
mov 56($inp), %rdx
adox %r11, %r11
# rbx <= 2 and rax <= 0xFFFF..F9, so carry must be zero here
adcx %rbx, %rax
adox %r11, %r11
adcx %rbp, $out
adox %r12, %r12
adcx %rax, %r11
adox %rbp, %rcx
@ -731,9 +731,9 @@ $code.=<<___;
#eighth iteration
mulx %rdx, %rax, %rdx
xor %rbx, %rbx
adox %r13, %r13
# rcx <= 2 and rax <= 0xFFFF..F9, so carry must be zero here
adcx %rcx, %rax
adox %r13, %r13
adcx %rbp, %rdx
adox %rbp, %rbx
adcx %r13, %rax
adcx %rdx, %rbx