crypto: x86/curve25519 - leave r12 as spare register

This updates to the newer register selection proved by HACL*, which
leads to a more compact instruction encoding, and saves around 100
cycles.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

diff --git a/arch/x86/crypto/curve25519-x86_64.c b/arch/x86/crypto/curve25519-x86_64.c
index e4e58b8..8a17621 100644 (file)
--- a/arch/x86/crypto/curve25519-x86_64.c
+++ b/arch/x86/crypto/curve25519-x86_64.c
@@ -167,28 +167,28 @@ static inline void fmul(u64 *out, const u64 *f1, const u64 *f2, u64 *tmp)
                "  movq 0(%1), %%rdx;"
                "  mulxq 0(%3), %%r8, %%r9;"       "  xor %%r10, %%r10;"     "  movq %%r8, 0(%0);"
                "  mulxq 8(%3), %%r10, %%r11;"     "  adox %%r9, %%r10;"     "  movq %%r10, 8(%0);"
-               "  mulxq 16(%3), %%r12, %%r13;"    "  adox %%r11, %%r12;"
+               "  mulxq 16(%3), %%rbx, %%r13;"    "  adox %%r11, %%rbx;"
                "  mulxq 24(%3), %%r14, %%rdx;"    "  adox %%r13, %%r14;"    "  mov $0, %%rax;"
                                                   "  adox %%rdx, %%rax;"
                /* Compute src1[1] * src2 */
                "  movq 8(%1), %%rdx;"
                "  mulxq 0(%3), %%r8, %%r9;"       "  xor %%r10, %%r10;"     "  adcxq 8(%0), %%r8;"    "  movq %%r8, 8(%0);"
-               "  mulxq 8(%3), %%r10, %%r11;"     "  adox %%r9, %%r10;"     "  adcx %%r12, %%r10;"    "  movq %%r10, 16(%0);"
-               "  mulxq 16(%3), %%r12, %%r13;"    "  adox %%r11, %%r12;"    "  adcx %%r14, %%r12;"    "  mov $0, %%r8;"
+               "  mulxq 8(%3), %%r10, %%r11;"     "  adox %%r9, %%r10;"     "  adcx %%rbx, %%r10;"    "  movq %%r10, 16(%0);"
+               "  mulxq 16(%3), %%rbx, %%r13;"    "  adox %%r11, %%rbx;"    "  adcx %%r14, %%rbx;"    "  mov $0, %%r8;"
                "  mulxq 24(%3), %%r14, %%rdx;"    "  adox %%r13, %%r14;"    "  adcx %%rax, %%r14;"    "  mov $0, %%rax;"
                                                   "  adox %%rdx, %%rax;"    "  adcx %%r8, %%rax;"
                /* Compute src1[2] * src2 */
                "  movq 16(%1), %%rdx;"
                "  mulxq 0(%3), %%r8, %%r9;"       "  xor %%r10, %%r10;"    "  adcxq 16(%0), %%r8;"    "  movq %%r8, 16(%0);"
-               "  mulxq 8(%3), %%r10, %%r11;"     "  adox %%r9, %%r10;"     "  adcx %%r12, %%r10;"    "  movq %%r10, 24(%0);"
-               "  mulxq 16(%3), %%r12, %%r13;"    "  adox %%r11, %%r12;"    "  adcx %%r14, %%r12;"    "  mov $0, %%r8;"
+               "  mulxq 8(%3), %%r10, %%r11;"     "  adox %%r9, %%r10;"     "  adcx %%rbx, %%r10;"    "  movq %%r10, 24(%0);"
+               "  mulxq 16(%3), %%rbx, %%r13;"    "  adox %%r11, %%rbx;"    "  adcx %%r14, %%rbx;"    "  mov $0, %%r8;"
                "  mulxq 24(%3), %%r14, %%rdx;"    "  adox %%r13, %%r14;"    "  adcx %%rax, %%r14;"    "  mov $0, %%rax;"
                                                   "  adox %%rdx, %%rax;"    "  adcx %%r8, %%rax;"
                /* Compute src1[3] * src2 */
                "  movq 24(%1), %%rdx;"
                "  mulxq 0(%3), %%r8, %%r9;"       "  xor %%r10, %%r10;"    "  adcxq 24(%0), %%r8;"    "  movq %%r8, 24(%0);"
-               "  mulxq 8(%3), %%r10, %%r11;"     "  adox %%r9, %%r10;"     "  adcx %%r12, %%r10;"    "  movq %%r10, 32(%0);"
-               "  mulxq 16(%3), %%r12, %%r13;"    "  adox %%r11, %%r12;"    "  adcx %%r14, %%r12;"    "  movq %%r12, 40(%0);"    "  mov $0, %%r8;"
+               "  mulxq 8(%3), %%r10, %%r11;"     "  adox %%r9, %%r10;"     "  adcx %%rbx, %%r10;"    "  movq %%r10, 32(%0);"
+               "  mulxq 16(%3), %%rbx, %%r13;"    "  adox %%r11, %%rbx;"    "  adcx %%r14, %%rbx;"    "  movq %%rbx, 40(%0);"    "  mov $0, %%r8;"
                "  mulxq 24(%3), %%r14, %%rdx;"    "  adox %%r13, %%r14;"    "  adcx %%rax, %%r14;"    "  movq %%r14, 48(%0);"    "  mov $0, %%rax;"
                                                   "  adox %%rdx, %%rax;"    "  adcx %%r8, %%rax;"     "  movq %%rax, 56(%0);"
                /* Line up pointers */
@@ -202,11 +202,11 @@ static inline void fmul(u64 *out, const u64 *f1, const u64 *f2, u64 *tmp)
                "  mulxq 32(%1), %%r8, %%r13;"
                "  xor %3, %3;"
                "  adoxq 0(%1), %%r8;"
-               "  mulxq 40(%1), %%r9, %%r12;"
+               "  mulxq 40(%1), %%r9, %%rbx;"
                "  adcx %%r13, %%r9;"
                "  adoxq 8(%1), %%r9;"
                "  mulxq 48(%1), %%r10, %%r13;"
-               "  adcx %%r12, %%r10;"
+               "  adcx %%rbx, %%r10;"
                "  adoxq 16(%1), %%r10;"
                "  mulxq 56(%1), %%r11, %%rax;"
                "  adcx %%r13, %%r11;"
@@ -231,7 +231,7 @@ static inline void fmul(u64 *out, const u64 *f1, const u64 *f2, u64 *tmp)
                "  movq %%r8, 0(%0);"
        : "+&r" (tmp), "+&r" (f1), "+&r" (out), "+&r" (f2)
        :
-       : "%rax", "%rdx", "%r8", "%r9", "%r10", "%r11", "%r12", "%r13", "%r14", "memory", "cc"
+       : "%rax", "%rdx", "%r8", "%r9", "%r10", "%r11", "%rbx", "%r13", "%r14", "memory", "cc"
        );
 }
 
@@ -248,28 +248,28 @@ static inline void fmul2(u64 *out, const u64 *f1, const u64 *f2, u64 *tmp)
                "  movq 0(%1), %%rdx;"
                "  mulxq 0(%3), %%r8, %%r9;"       "  xor %%r10, %%r10;"     "  movq %%r8, 0(%0);"
                "  mulxq 8(%3), %%r10, %%r11;"     "  adox %%r9, %%r10;"     "  movq %%r10, 8(%0);"
-               "  mulxq 16(%3), %%r12, %%r13;"    "  adox %%r11, %%r12;"
+               "  mulxq 16(%3), %%rbx, %%r13;"    "  adox %%r11, %%rbx;"
                "  mulxq 24(%3), %%r14, %%rdx;"    "  adox %%r13, %%r14;"    "  mov $0, %%rax;"
                                                   "  adox %%rdx, %%rax;"
                /* Compute src1[1] * src2 */
                "  movq 8(%1), %%rdx;"
                "  mulxq 0(%3), %%r8, %%r9;"       "  xor %%r10, %%r10;"     "  adcxq 8(%0), %%r8;"    "  movq %%r8, 8(%0);"
-               "  mulxq 8(%3), %%r10, %%r11;"     "  adox %%r9, %%r10;"     "  adcx %%r12, %%r10;"    "  movq %%r10, 16(%0);"
-               "  mulxq 16(%3), %%r12, %%r13;"    "  adox %%r11, %%r12;"    "  adcx %%r14, %%r12;"    "  mov $0, %%r8;"
+               "  mulxq 8(%3), %%r10, %%r11;"     "  adox %%r9, %%r10;"     "  adcx %%rbx, %%r10;"    "  movq %%r10, 16(%0);"
+               "  mulxq 16(%3), %%rbx, %%r13;"    "  adox %%r11, %%rbx;"    "  adcx %%r14, %%rbx;"    "  mov $0, %%r8;"
                "  mulxq 24(%3), %%r14, %%rdx;"    "  adox %%r13, %%r14;"    "  adcx %%rax, %%r14;"    "  mov $0, %%rax;"
                                                   "  adox %%rdx, %%rax;"    "  adcx %%r8, %%rax;"
                /* Compute src1[2] * src2 */
                "  movq 16(%1), %%rdx;"
                "  mulxq 0(%3), %%r8, %%r9;"       "  xor %%r10, %%r10;"    "  adcxq 16(%0), %%r8;"    "  movq %%r8, 16(%0);"
-               "  mulxq 8(%3), %%r10, %%r11;"     "  adox %%r9, %%r10;"     "  adcx %%r12, %%r10;"    "  movq %%r10, 24(%0);"
-               "  mulxq 16(%3), %%r12, %%r13;"    "  adox %%r11, %%r12;"    "  adcx %%r14, %%r12;"    "  mov $0, %%r8;"
+               "  mulxq 8(%3), %%r10, %%r11;"     "  adox %%r9, %%r10;"     "  adcx %%rbx, %%r10;"    "  movq %%r10, 24(%0);"
+               "  mulxq 16(%3), %%rbx, %%r13;"    "  adox %%r11, %%rbx;"    "  adcx %%r14, %%rbx;"    "  mov $0, %%r8;"
                "  mulxq 24(%3), %%r14, %%rdx;"    "  adox %%r13, %%r14;"    "  adcx %%rax, %%r14;"    "  mov $0, %%rax;"
                                                   "  adox %%rdx, %%rax;"    "  adcx %%r8, %%rax;"
                /* Compute src1[3] * src2 */
                "  movq 24(%1), %%rdx;"
                "  mulxq 0(%3), %%r8, %%r9;"       "  xor %%r10, %%r10;"    "  adcxq 24(%0), %%r8;"    "  movq %%r8, 24(%0);"
-               "  mulxq 8(%3), %%r10, %%r11;"     "  adox %%r9, %%r10;"     "  adcx %%r12, %%r10;"    "  movq %%r10, 32(%0);"
-               "  mulxq 16(%3), %%r12, %%r13;"    "  adox %%r11, %%r12;"    "  adcx %%r14, %%r12;"    "  movq %%r12, 40(%0);"    "  mov $0, %%r8;"
+               "  mulxq 8(%3), %%r10, %%r11;"     "  adox %%r9, %%r10;"     "  adcx %%rbx, %%r10;"    "  movq %%r10, 32(%0);"
+               "  mulxq 16(%3), %%rbx, %%r13;"    "  adox %%r11, %%rbx;"    "  adcx %%r14, %%rbx;"    "  movq %%rbx, 40(%0);"    "  mov $0, %%r8;"
                "  mulxq 24(%3), %%r14, %%rdx;"    "  adox %%r13, %%r14;"    "  adcx %%rax, %%r14;"    "  movq %%r14, 48(%0);"    "  mov $0, %%rax;"
                                                   "  adox %%rdx, %%rax;"    "  adcx %%r8, %%rax;"     "  movq %%rax, 56(%0);"
 
@@ -279,28 +279,28 @@ static inline void fmul2(u64 *out, const u64 *f1, const u64 *f2, u64 *tmp)
                "  movq 32(%1), %%rdx;"
                "  mulxq 32(%3), %%r8, %%r9;"       "  xor %%r10, %%r10;"     "  movq %%r8, 64(%0);"
                "  mulxq 40(%3), %%r10, %%r11;"     "  adox %%r9, %%r10;"     "  movq %%r10, 72(%0);"
-               "  mulxq 48(%3), %%r12, %%r13;"    "  adox %%r11, %%r12;"
+               "  mulxq 48(%3), %%rbx, %%r13;"    "  adox %%r11, %%rbx;"
                "  mulxq 56(%3), %%r14, %%rdx;"    "  adox %%r13, %%r14;"    "  mov $0, %%rax;"
                                                   "  adox %%rdx, %%rax;"
                /* Compute src1[1] * src2 */
                "  movq 40(%1), %%rdx;"
                "  mulxq 32(%3), %%r8, %%r9;"       "  xor %%r10, %%r10;"     "  adcxq 72(%0), %%r8;"    "  movq %%r8, 72(%0);"
-               "  mulxq 40(%3), %%r10, %%r11;"     "  adox %%r9, %%r10;"     "  adcx %%r12, %%r10;"    "  movq %%r10, 80(%0);"
-               "  mulxq 48(%3), %%r12, %%r13;"    "  adox %%r11, %%r12;"    "  adcx %%r14, %%r12;"    "  mov $0, %%r8;"
+               "  mulxq 40(%3), %%r10, %%r11;"     "  adox %%r9, %%r10;"     "  adcx %%rbx, %%r10;"    "  movq %%r10, 80(%0);"
+               "  mulxq 48(%3), %%rbx, %%r13;"    "  adox %%r11, %%rbx;"    "  adcx %%r14, %%rbx;"    "  mov $0, %%r8;"
                "  mulxq 56(%3), %%r14, %%rdx;"    "  adox %%r13, %%r14;"    "  adcx %%rax, %%r14;"    "  mov $0, %%rax;"
                                                   "  adox %%rdx, %%rax;"    "  adcx %%r8, %%rax;"
                /* Compute src1[2] * src2 */
                "  movq 48(%1), %%rdx;"
                "  mulxq 32(%3), %%r8, %%r9;"       "  xor %%r10, %%r10;"    "  adcxq 80(%0), %%r8;"    "  movq %%r8, 80(%0);"
-               "  mulxq 40(%3), %%r10, %%r11;"     "  adox %%r9, %%r10;"     "  adcx %%r12, %%r10;"    "  movq %%r10, 88(%0);"
-               "  mulxq 48(%3), %%r12, %%r13;"    "  adox %%r11, %%r12;"    "  adcx %%r14, %%r12;"    "  mov $0, %%r8;"
+               "  mulxq 40(%3), %%r10, %%r11;"     "  adox %%r9, %%r10;"     "  adcx %%rbx, %%r10;"    "  movq %%r10, 88(%0);"
+               "  mulxq 48(%3), %%rbx, %%r13;"    "  adox %%r11, %%rbx;"    "  adcx %%r14, %%rbx;"    "  mov $0, %%r8;"
                "  mulxq 56(%3), %%r14, %%rdx;"    "  adox %%r13, %%r14;"    "  adcx %%rax, %%r14;"    "  mov $0, %%rax;"
                                                   "  adox %%rdx, %%rax;"    "  adcx %%r8, %%rax;"
                /* Compute src1[3] * src2 */
                "  movq 56(%1), %%rdx;"
                "  mulxq 32(%3), %%r8, %%r9;"       "  xor %%r10, %%r10;"    "  adcxq 88(%0), %%r8;"    "  movq %%r8, 88(%0);"
-               "  mulxq 40(%3), %%r10, %%r11;"     "  adox %%r9, %%r10;"     "  adcx %%r12, %%r10;"    "  movq %%r10, 96(%0);"
-               "  mulxq 48(%3), %%r12, %%r13;"    "  adox %%r11, %%r12;"    "  adcx %%r14, %%r12;"    "  movq %%r12, 104(%0);"    "  mov $0, %%r8;"
+               "  mulxq 40(%3), %%r10, %%r11;"     "  adox %%r9, %%r10;"     "  adcx %%rbx, %%r10;"    "  movq %%r10, 96(%0);"
+               "  mulxq 48(%3), %%rbx, %%r13;"    "  adox %%r11, %%rbx;"    "  adcx %%r14, %%rbx;"    "  movq %%rbx, 104(%0);"    "  mov $0, %%r8;"
                "  mulxq 56(%3), %%r14, %%rdx;"    "  adox %%r13, %%r14;"    "  adcx %%rax, %%r14;"    "  movq %%r14, 112(%0);"    "  mov $0, %%rax;"
                                                   "  adox %%rdx, %%rax;"    "  adcx %%r8, %%rax;"     "  movq %%rax, 120(%0);"
                /* Line up pointers */
@@ -314,11 +314,11 @@ static inline void fmul2(u64 *out, const u64 *f1, const u64 *f2, u64 *tmp)
                "  mulxq 32(%1), %%r8, %%r13;"
                "  xor %3, %3;"
                "  adoxq 0(%1), %%r8;"
-               "  mulxq 40(%1), %%r9, %%r12;"
+               "  mulxq 40(%1), %%r9, %%rbx;"
                "  adcx %%r13, %%r9;"
                "  adoxq 8(%1), %%r9;"
                "  mulxq 48(%1), %%r10, %%r13;"
-               "  adcx %%r12, %%r10;"
+               "  adcx %%rbx, %%r10;"
                "  adoxq 16(%1), %%r10;"
                "  mulxq 56(%1), %%r11, %%rax;"
                "  adcx %%r13, %%r11;"
@@ -347,11 +347,11 @@ static inline void fmul2(u64 *out, const u64 *f1, const u64 *f2, u64 *tmp)
                "  mulxq 96(%1), %%r8, %%r13;"
                "  xor %3, %3;"
                "  adoxq 64(%1), %%r8;"
-               "  mulxq 104(%1), %%r9, %%r12;"
+               "  mulxq 104(%1), %%r9, %%rbx;"
                "  adcx %%r13, %%r9;"
                "  adoxq 72(%1), %%r9;"
                "  mulxq 112(%1), %%r10, %%r13;"
-               "  adcx %%r12, %%r10;"
+               "  adcx %%rbx, %%r10;"
                "  adoxq 80(%1), %%r10;"
                "  mulxq 120(%1), %%r11, %%rax;"
                "  adcx %%r13, %%r11;"
@@ -376,7 +376,7 @@ static inline void fmul2(u64 *out, const u64 *f1, const u64 *f2, u64 *tmp)
                "  movq %%r8, 32(%0);"
        : "+&r" (tmp), "+&r" (f1), "+&r" (out), "+&r" (f2)
        :
-       : "%rax", "%rdx", "%r8", "%r9", "%r10", "%r11", "%r12", "%r13", "%r14", "memory", "cc"
+       : "%rax", "%rdx", "%r8", "%r9", "%r10", "%r11", "%rbx", "%r13", "%r14", "memory", "cc"
        );
 }
 
@@ -388,11 +388,11 @@ static inline void fmul_scalar(u64 *out, const u64 *f1, u64 f2)
        asm volatile(
                /* Compute the raw multiplication of f1*f2 */
                "  mulxq 0(%2), %%r8, %%rcx;"      /* f1[0]*f2 */
-               "  mulxq 8(%2), %%r9, %%r12;"      /* f1[1]*f2 */
+               "  mulxq 8(%2), %%r9, %%rbx;"      /* f1[1]*f2 */
                "  add %%rcx, %%r9;"
                "  mov $0, %%rcx;"
                "  mulxq 16(%2), %%r10, %%r13;"    /* f1[2]*f2 */
-               "  adcx %%r12, %%r10;"
+               "  adcx %%rbx, %%r10;"
                "  mulxq 24(%2), %%r11, %%rax;"    /* f1[3]*f2 */
                "  adcx %%r13, %%r11;"
                "  adcx %%rcx, %%rax;"
@@ -419,7 +419,7 @@ static inline void fmul_scalar(u64 *out, const u64 *f1, u64 f2)
                "  movq %%r8, 0(%1);"
        : "+&r" (f2_r)
        : "r" (out), "r" (f1)
-       : "%rax", "%rcx", "%r8", "%r9", "%r10", "%r11", "%r12", "%r13", "memory", "cc"
+       : "%rax", "%rcx", "%r8", "%r9", "%r10", "%r11", "%rbx", "%r13", "memory", "cc"
        );
 }
 
@@ -520,8 +520,8 @@ static inline void fsqr(u64 *out, const u64 *f, u64 *tmp)
                "  mulxq 16(%1), %%r9, %%r10;"     "  adcx %%r14, %%r9;"     /* f[2]*f[0] */
                "  mulxq 24(%1), %%rax, %%rcx;"    "  adcx %%rax, %%r10;"    /* f[3]*f[0] */
                "  movq 24(%1), %%rdx;"                                      /* f[3] */
-               "  mulxq 8(%1), %%r11, %%r12;"     "  adcx %%rcx, %%r11;"    /* f[1]*f[3] */
-               "  mulxq 16(%1), %%rax, %%r13;"    "  adcx %%rax, %%r12;"    /* f[2]*f[3] */
+               "  mulxq 8(%1), %%r11, %%rbx;"     "  adcx %%rcx, %%r11;"    /* f[1]*f[3] */
+               "  mulxq 16(%1), %%rax, %%r13;"    "  adcx %%rax, %%rbx;"    /* f[2]*f[3] */
                "  movq 8(%1), %%rdx;"             "  adcx %%r15, %%r13;"    /* f1 */
                "  mulxq 16(%1), %%rax, %%rcx;"    "  mov $0, %%r14;"        /* f[2]*f[1] */
 
@@ -531,12 +531,12 @@ static inline void fsqr(u64 *out, const u64 *f, u64 *tmp)
                "  adcx %%r8, %%r8;"
                "  adox %%rcx, %%r11;"
                "  adcx %%r9, %%r9;"
-               "  adox %%r15, %%r12;"
+               "  adox %%r15, %%rbx;"
                "  adcx %%r10, %%r10;"
                "  adox %%r15, %%r13;"
                "  adcx %%r11, %%r11;"
                "  adox %%r15, %%r14;"
-               "  adcx %%r12, %%r12;"
+               "  adcx %%rbx, %%rbx;"
                "  adcx %%r13, %%r13;"
                "  adcx %%r14, %%r14;"
 
@@ -549,7 +549,7 @@ static inline void fsqr(u64 *out, const u64 *f, u64 *tmp)
                "  adcx %%rcx, %%r10;"     "  movq %%r10, 24(%0);"
                "  movq 16(%1), %%rdx;"    "  mulx %%rdx, %%rax, %%rcx;"    /* f[2]^2 */
                "  adcx %%rax, %%r11;"     "  movq %%r11, 32(%0);"
-               "  adcx %%rcx, %%r12;"     "  movq %%r12, 40(%0);"
+               "  adcx %%rcx, %%rbx;"     "  movq %%rbx, 40(%0);"
                "  movq 24(%1), %%rdx;"    "  mulx %%rdx, %%rax, %%rcx;"    /* f[3]^2 */
                "  adcx %%rax, %%r13;"     "  movq %%r13, 48(%0);"
                "  adcx %%rcx, %%r14;"     "  movq %%r14, 56(%0);"
@@ -565,11 +565,11 @@ static inline void fsqr(u64 *out, const u64 *f, u64 *tmp)
                "  mulxq 32(%1), %%r8, %%r13;"
                "  xor %%rcx, %%rcx;"
                "  adoxq 0(%1), %%r8;"
-               "  mulxq 40(%1), %%r9, %%r12;"
+               "  mulxq 40(%1), %%r9, %%rbx;"
                "  adcx %%r13, %%r9;"
                "  adoxq 8(%1), %%r9;"
                "  mulxq 48(%1), %%r10, %%r13;"
-               "  adcx %%r12, %%r10;"
+               "  adcx %%rbx, %%r10;"
                "  adoxq 16(%1), %%r10;"
                "  mulxq 56(%1), %%r11, %%rax;"
                "  adcx %%r13, %%r11;"
@@ -594,7 +594,7 @@ static inline void fsqr(u64 *out, const u64 *f, u64 *tmp)
                "  movq %%r8, 0(%0);"
        : "+&r" (tmp), "+&r" (f), "+&r" (out)
        :
-       : "%rax", "%rcx", "%rdx", "%r8", "%r9", "%r10", "%r11", "%r12", "%r13", "%r14", "%r15", "memory", "cc"
+       : "%rax", "%rcx", "%rdx", "%r8", "%r9", "%r10", "%r11", "%rbx", "%r13", "%r14", "%r15", "memory", "cc"
        );
 }
 
@@ -611,8 +611,8 @@ static inline void fsqr2(u64 *out, const u64 *f, u64 *tmp)
                "  mulxq 16(%1), %%r9, %%r10;"     "  adcx %%r14, %%r9;"     /* f[2]*f[0] */
                "  mulxq 24(%1), %%rax, %%rcx;"    "  adcx %%rax, %%r10;"    /* f[3]*f[0] */
                "  movq 24(%1), %%rdx;"                                      /* f[3] */
-               "  mulxq 8(%1), %%r11, %%r12;"     "  adcx %%rcx, %%r11;"    /* f[1]*f[3] */
-               "  mulxq 16(%1), %%rax, %%r13;"    "  adcx %%rax, %%r12;"    /* f[2]*f[3] */
+               "  mulxq 8(%1), %%r11, %%rbx;"     "  adcx %%rcx, %%r11;"    /* f[1]*f[3] */
+               "  mulxq 16(%1), %%rax, %%r13;"    "  adcx %%rax, %%rbx;"    /* f[2]*f[3] */
                "  movq 8(%1), %%rdx;"             "  adcx %%r15, %%r13;"    /* f1 */
                "  mulxq 16(%1), %%rax, %%rcx;"    "  mov $0, %%r14;"        /* f[2]*f[1] */
 
@@ -622,12 +622,12 @@ static inline void fsqr2(u64 *out, const u64 *f, u64 *tmp)
                "  adcx %%r8, %%r8;"
                "  adox %%rcx, %%r11;"
                "  adcx %%r9, %%r9;"
-               "  adox %%r15, %%r12;"
+               "  adox %%r15, %%rbx;"
                "  adcx %%r10, %%r10;"
                "  adox %%r15, %%r13;"
                "  adcx %%r11, %%r11;"
                "  adox %%r15, %%r14;"
-               "  adcx %%r12, %%r12;"
+               "  adcx %%rbx, %%rbx;"
                "  adcx %%r13, %%r13;"
                "  adcx %%r14, %%r14;"
 
@@ -640,7 +640,7 @@ static inline void fsqr2(u64 *out, const u64 *f, u64 *tmp)
                "  adcx %%rcx, %%r10;"     "  movq %%r10, 24(%0);"
                "  movq 16(%1), %%rdx;"    "  mulx %%rdx, %%rax, %%rcx;"    /* f[2]^2 */
                "  adcx %%rax, %%r11;"     "  movq %%r11, 32(%0);"
-               "  adcx %%rcx, %%r12;"     "  movq %%r12, 40(%0);"
+               "  adcx %%rcx, %%rbx;"     "  movq %%rbx, 40(%0);"
                "  movq 24(%1), %%rdx;"    "  mulx %%rdx, %%rax, %%rcx;"    /* f[3]^2 */
                "  adcx %%rax, %%r13;"     "  movq %%r13, 48(%0);"
                "  adcx %%rcx, %%r14;"     "  movq %%r14, 56(%0);"
@@ -651,8 +651,8 @@ static inline void fsqr2(u64 *out, const u64 *f, u64 *tmp)
                "  mulxq 48(%1), %%r9, %%r10;"     "  adcx %%r14, %%r9;"     /* f[2]*f[0] */
                "  mulxq 56(%1), %%rax, %%rcx;"    "  adcx %%rax, %%r10;"    /* f[3]*f[0] */
                "  movq 56(%1), %%rdx;"                                      /* f[3] */
-               "  mulxq 40(%1), %%r11, %%r12;"     "  adcx %%rcx, %%r11;"    /* f[1]*f[3] */
-               "  mulxq 48(%1), %%rax, %%r13;"    "  adcx %%rax, %%r12;"    /* f[2]*f[3] */
+               "  mulxq 40(%1), %%r11, %%rbx;"     "  adcx %%rcx, %%r11;"    /* f[1]*f[3] */
+               "  mulxq 48(%1), %%rax, %%r13;"    "  adcx %%rax, %%rbx;"    /* f[2]*f[3] */
                "  movq 40(%1), %%rdx;"             "  adcx %%r15, %%r13;"    /* f1 */
                "  mulxq 48(%1), %%rax, %%rcx;"    "  mov $0, %%r14;"        /* f[2]*f[1] */
 
@@ -662,12 +662,12 @@ static inline void fsqr2(u64 *out, const u64 *f, u64 *tmp)
                "  adcx %%r8, %%r8;"
                "  adox %%rcx, %%r11;"
                "  adcx %%r9, %%r9;"
-               "  adox %%r15, %%r12;"
+               "  adox %%r15, %%rbx;"
                "  adcx %%r10, %%r10;"
                "  adox %%r15, %%r13;"
                "  adcx %%r11, %%r11;"
                "  adox %%r15, %%r14;"
-               "  adcx %%r12, %%r12;"
+               "  adcx %%rbx, %%rbx;"
                "  adcx %%r13, %%r13;"
                "  adcx %%r14, %%r14;"
 
@@ -680,7 +680,7 @@ static inline void fsqr2(u64 *out, const u64 *f, u64 *tmp)
                "  adcx %%rcx, %%r10;"     "  movq %%r10, 88(%0);"
                "  movq 48(%1), %%rdx;"    "  mulx %%rdx, %%rax, %%rcx;"    /* f[2]^2 */
                "  adcx %%rax, %%r11;"     "  movq %%r11, 96(%0);"
-               "  adcx %%rcx, %%r12;"     "  movq %%r12, 104(%0);"
+               "  adcx %%rcx, %%rbx;"     "  movq %%rbx, 104(%0);"
                "  movq 56(%1), %%rdx;"    "  mulx %%rdx, %%rax, %%rcx;"    /* f[3]^2 */
                "  adcx %%rax, %%r13;"     "  movq %%r13, 112(%0);"
                "  adcx %%rcx, %%r14;"     "  movq %%r14, 120(%0);"
@@ -694,11 +694,11 @@ static inline void fsqr2(u64 *out, const u64 *f, u64 *tmp)
                "  mulxq 32(%1), %%r8, %%r13;"
                "  xor %%rcx, %%rcx;"
                "  adoxq 0(%1), %%r8;"
-               "  mulxq 40(%1), %%r9, %%r12;"
+               "  mulxq 40(%1), %%r9, %%rbx;"
                "  adcx %%r13, %%r9;"
                "  adoxq 8(%1), %%r9;"
                "  mulxq 48(%1), %%r10, %%r13;"
-               "  adcx %%r12, %%r10;"
+               "  adcx %%rbx, %%r10;"
                "  adoxq 16(%1), %%r10;"
                "  mulxq 56(%1), %%r11, %%rax;"
                "  adcx %%r13, %%r11;"
@@ -727,11 +727,11 @@ static inline void fsqr2(u64 *out, const u64 *f, u64 *tmp)
                "  mulxq 96(%1), %%r8, %%r13;"
                "  xor %%rcx, %%rcx;"
                "  adoxq 64(%1), %%r8;"
-               "  mulxq 104(%1), %%r9, %%r12;"
+               "  mulxq 104(%1), %%r9, %%rbx;"
                "  adcx %%r13, %%r9;"
                "  adoxq 72(%1), %%r9;"
                "  mulxq 112(%1), %%r10, %%r13;"
-               "  adcx %%r12, %%r10;"
+               "  adcx %%rbx, %%r10;"
                "  adoxq 80(%1), %%r10;"
                "  mulxq 120(%1), %%r11, %%rax;"
                "  adcx %%r13, %%r11;"
@@ -756,7 +756,7 @@ static inline void fsqr2(u64 *out, const u64 *f, u64 *tmp)
                "  movq %%r8, 32(%0);"
        : "+&r" (tmp), "+&r" (f), "+&r" (out)
        :
-       : "%rax", "%rcx", "%rdx", "%r8", "%r9", "%r10", "%r11", "%r12", "%r13", "%r14", "%r15", "memory", "cc"
+       : "%rax", "%rcx", "%rdx", "%r8", "%r9", "%r10", "%r11", "%rbx", "%r13", "%r14", "%r15", "memory", "cc"
        );
 }