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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 7753a3a684)

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

Reviewed-by: Rich Salz <rsalz@openssl.org>
(cherry picked from commit a90b1e32d2)
This commit is contained in:
Adam Langley
2013-06-03 15:45:11 -04:00
committed by Emilia Kasper
parent bf3e53a7fa
commit fee8d86d7a
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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@@ -185,7 +185,7 @@ 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"
".align 16 \n"
"1: movq (%4,%2,8),%0 \n"
@@ -196,7 +196,7 @@ 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;
@@ -208,7 +208,7 @@ 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"
".align 16 \n"
"1: movq (%4,%2,8),%0 \n"
@@ -219,7 +219,7 @@ 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;