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Add volatile qualifications to two blocks of inline asm to stop GCC from

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eliminating them as dead code.

Both volatile and "memory" are used because of some concern that the compiler
may still cache values across the asm block without it, and because this was
such a painful debugging session that I wanted to ensure that it's never
repeated.

(cherry picked from commit 7753a3a68431aa81b82beea4c3f5374b41454679)

Conflicts:
	crypto/bn/asm/x86_64-gcc.c

Reviewed-by: Rich Salz <rsalz@openssl.org>
(cherry picked from commit a90b1e32d2f697d1aa39b49038469e2ea40d5e7b)
This commit is contained in:
Adam Langley 2013-06-03 15:45:11 -04:00 committed by Emilia Kasper
parent 679d0c8655
commit e164b34079
1 changed files with 4 additions and 4 deletions
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8
crypto/bn/asm/x86_64-gcc.c
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@ -189,7 +189,7 @@ BN_ULONG bn_add_words (BN_ULONG *rp, const BN_ULONG *ap, const BN_ULONG *bp,int
if (n <= 0) return 0;
asm (
asm volatile (
" subq %2,%2 \n"
".p2align 4 \n"
"1: movq (%4,%2,8),%0 \n"
@ -200,7 +200,7 @@ BN_ULONG bn_add_words (BN_ULONG *rp, const BN_ULONG *ap, const BN_ULONG *bp,int
" sbbq %0,%0 \n"
: "=&a"(ret),"+c"(n),"=&r"(i)
: "r"(rp),"r"(ap),"r"(bp)
: "cc"
: "cc", "memory"
);
return ret&1;
@ -212,7 +212,7 @@ BN_ULONG bn_sub_words (BN_ULONG *rp, const BN_ULONG *ap, const BN_ULONG *bp,int
if (n <= 0) return 0;
asm (
asm volatile (
" subq %2,%2 \n"
".p2align 4 \n"
"1: movq (%4,%2,8),%0 \n"
@ -223,7 +223,7 @@ BN_ULONG bn_sub_words (BN_ULONG *rp, const BN_ULONG *ap, const BN_ULONG *bp,int
" sbbq %0,%0 \n"
: "=&a"(ret),"+c"(n),"=&r"(i)
: "r"(rp),"r"(ap),"r"(bp)
: "cc"
: "cc", "memory"
);
return ret&1;