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

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>

diff --git a/crypto/bn/asm/x86_64-gcc.c b/crypto/bn/asm/x86_64-gcc.c
index acb0b401181e32983b94d7ce19c002b41585f31b..31476abebfb79b892cb5f5d86b0ffdf47811993a 100644 (file)
--- a/crypto/bn/asm/x86_64-gcc.c
+++ b/crypto/bn/asm/x86_64-gcc.c
@@ -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;