Hi Uros, Thanks for this patch. This seems correct to me, since indeed those clear the top bits anyway, and having smaller code seems good. But first -- I'm wondering -- have you stuck this into Vale/Hacl to see if it still checks out there? I'm CC'ing Karthik/Aymeric/Chris/Jonathan who might be interested in taking a look at that. Seems like it might be easy to just special case this in Xor64 for the case where the operands are the same. Also, have you seen any measurable differences when benching this? I can stick it into kbench9000 to see if you haven't looked yet. Jason On Tue, Sep 1, 2020 at 5:46 PM Ard Biesheuvel <ardb@xxxxxxxxxx> wrote: > > (+ Jason) > > On Thu, 27 Aug 2020 at 20:31, Uros Bizjak <ubizjak@xxxxxxxxx> wrote: > > > > x86_64 zero extends 32bit operations, so for 64bit operands, > > XORL r32,r32 is functionally equal to XORL r64,r64, but avoids > > a REX prefix byte when legacy registers are used. > > > > Signed-off-by: Uros Bizjak <ubizjak@xxxxxxxxx> > > Cc: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx> > > Cc: "David S. Miller" <davem@xxxxxxxxxxxxx> > > --- > > arch/x86/crypto/curve25519-x86_64.c | 68 ++++++++++++++--------------- > > 1 file changed, 34 insertions(+), 34 deletions(-) > > > > diff --git a/arch/x86/crypto/curve25519-x86_64.c b/arch/x86/crypto/curve25519-x86_64.c > > index 8acbb6584a37..a9edb6f8a0ba 100644 > > --- a/arch/x86/crypto/curve25519-x86_64.c > > +++ b/arch/x86/crypto/curve25519-x86_64.c > > @@ -45,11 +45,11 @@ static inline u64 add_scalar(u64 *out, const u64 *f1, u64 f2) > > > > asm volatile( > > /* Clear registers to propagate the carry bit */ > > - " xor %%r8, %%r8;" > > - " xor %%r9, %%r9;" > > - " xor %%r10, %%r10;" > > - " xor %%r11, %%r11;" > > - " xor %1, %1;" > > + " xor %%r8d, %%r8d;" > > + " xor %%r9d, %%r9d;" > > + " xor %%r10d, %%r10d;" > > + " xor %%r11d, %%r11d;" > > + " xor %k1, %k1;" > > > > /* Begin addition chain */ > > " addq 0(%3), %0;" > > @@ -93,7 +93,7 @@ static inline void fadd(u64 *out, const u64 *f1, const u64 *f2) > > " cmovc %0, %%rax;" > > > > /* Step 2: Add carry*38 to the original sum */ > > - " xor %%rcx, %%rcx;" > > + " xor %%ecx, %%ecx;" > > " add %%rax, %%r8;" > > " adcx %%rcx, %%r9;" > > " movq %%r9, 8(%1);" > > @@ -165,28 +165,28 @@ static inline void fmul(u64 *out, const u64 *f1, const u64 *f2, u64 *tmp) > > > > /* Compute src1[0] * src2 */ > > " movq 0(%1), %%rdx;" > > - " mulxq 0(%3), %%r8, %%r9;" " xor %%r10, %%r10;" " movq %%r8, 0(%0);" > > + " mulxq 0(%3), %%r8, %%r9;" " xor %%r10d, %%r10d;" " movq %%r8, 0(%0);" > > " mulxq 8(%3), %%r10, %%r11;" " adox %%r9, %%r10;" " movq %%r10, 8(%0);" > > " 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 0(%3), %%r8, %%r9;" " xor %%r10d, %%r10d;" " adcxq 8(%0), %%r8;" " movq %%r8, 8(%0);" > > " 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 0(%3), %%r8, %%r9;" " xor %%r10d, %%r10d;" " adcxq 16(%0), %%r8;" " movq %%r8, 16(%0);" > > " 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 0(%3), %%r8, %%r9;" " xor %%r10d, %%r10d;" " adcxq 24(%0), %%r8;" " movq %%r8, 24(%0);" > > " 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;" > > @@ -200,7 +200,7 @@ static inline void fmul(u64 *out, const u64 *f1, const u64 *f2, u64 *tmp) > > /* Step 1: Compute dst + carry == tmp_hi * 38 + tmp_lo */ > > " mov $38, %%rdx;" > > " mulxq 32(%1), %%r8, %%r13;" > > - " xor %3, %3;" > > + " xor %k3, %k3;" > > " adoxq 0(%1), %%r8;" > > " mulxq 40(%1), %%r9, %%rbx;" > > " adcx %%r13, %%r9;" > > @@ -246,28 +246,28 @@ static inline void fmul2(u64 *out, const u64 *f1, const u64 *f2, u64 *tmp) > > > > /* Compute src1[0] * src2 */ > > " movq 0(%1), %%rdx;" > > - " mulxq 0(%3), %%r8, %%r9;" " xor %%r10, %%r10;" " movq %%r8, 0(%0);" > > + " mulxq 0(%3), %%r8, %%r9;" " xor %%r10d, %%r10d;" " movq %%r8, 0(%0);" > > " mulxq 8(%3), %%r10, %%r11;" " adox %%r9, %%r10;" " movq %%r10, 8(%0);" > > " 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 0(%3), %%r8, %%r9;" " xor %%r10d, %%r10d;" " adcxq 8(%0), %%r8;" " movq %%r8, 8(%0);" > > " 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 0(%3), %%r8, %%r9;" " xor %%r10d, %%r10d;" " adcxq 16(%0), %%r8;" " movq %%r8, 16(%0);" > > " 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 0(%3), %%r8, %%r9;" " xor %%r10d, %%r10d;" " adcxq 24(%0), %%r8;" " movq %%r8, 24(%0);" > > " 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;" > > @@ -277,29 +277,29 @@ static inline void fmul2(u64 *out, const u64 *f1, const u64 *f2, u64 *tmp) > > > > /* Compute src1[0] * src2 */ > > " 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 32(%3), %%r8, %%r9;" " xor %%r10d, %%r10d;" " movq %%r8, 64(%0);" > > + " mulxq 40(%3), %%r10, %%r11;" " adox %%r9, %%r10;" " movq %%r10, 72(%0);" > > " 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 %%rbx, %%r10;" " movq %%r10, 80(%0);" > > + " mulxq 32(%3), %%r8, %%r9;" " xor %%r10d, %%r10d;" " adcxq 72(%0), %%r8;" " movq %%r8, 72(%0);" > > + " 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 %%rbx, %%r10;" " movq %%r10, 88(%0);" > > + " mulxq 32(%3), %%r8, %%r9;" " xor %%r10d, %%r10d;" " adcxq 80(%0), %%r8;" " movq %%r8, 80(%0);" > > + " 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 %%rbx, %%r10;" " movq %%r10, 96(%0);" > > + " mulxq 32(%3), %%r8, %%r9;" " xor %%r10d, %%r10d;" " adcxq 88(%0), %%r8;" " movq %%r8, 88(%0);" > > + " 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);" > > @@ -312,7 +312,7 @@ static inline void fmul2(u64 *out, const u64 *f1, const u64 *f2, u64 *tmp) > > /* Step 1: Compute dst + carry == tmp_hi * 38 + tmp_lo */ > > " mov $38, %%rdx;" > > " mulxq 32(%1), %%r8, %%r13;" > > - " xor %3, %3;" > > + " xor %k3, %k3;" > > " adoxq 0(%1), %%r8;" > > " mulxq 40(%1), %%r9, %%rbx;" > > " adcx %%r13, %%r9;" > > @@ -345,7 +345,7 @@ static inline void fmul2(u64 *out, const u64 *f1, const u64 *f2, u64 *tmp) > > /* Step 1: Compute dst + carry == tmp_hi * 38 + tmp_lo */ > > " mov $38, %%rdx;" > > " mulxq 96(%1), %%r8, %%r13;" > > - " xor %3, %3;" > > + " xor %k3, %k3;" > > " adoxq 64(%1), %%r8;" > > " mulxq 104(%1), %%r9, %%rbx;" > > " adcx %%r13, %%r9;" > > @@ -516,7 +516,7 @@ static inline void fsqr(u64 *out, const u64 *f, u64 *tmp) > > > > /* Step 1: Compute all partial products */ > > " movq 0(%1), %%rdx;" /* f[0] */ > > - " mulxq 8(%1), %%r8, %%r14;" " xor %%r15, %%r15;" /* f[1]*f[0] */ > > + " mulxq 8(%1), %%r8, %%r14;" " xor %%r15d, %%r15d;" /* f[1]*f[0] */ > > " 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] */ > > @@ -526,7 +526,7 @@ static inline void fsqr(u64 *out, const u64 *f, u64 *tmp) > > " mulxq 16(%1), %%rax, %%rcx;" " mov $0, %%r14;" /* f[2]*f[1] */ > > > > /* Step 2: Compute two parallel carry chains */ > > - " xor %%r15, %%r15;" > > + " xor %%r15d, %%r15d;" > > " adox %%rax, %%r10;" > > " adcx %%r8, %%r8;" > > " adox %%rcx, %%r11;" > > @@ -563,7 +563,7 @@ static inline void fsqr(u64 *out, const u64 *f, u64 *tmp) > > /* Step 1: Compute dst + carry == tmp_hi * 38 + tmp_lo */ > > " mov $38, %%rdx;" > > " mulxq 32(%1), %%r8, %%r13;" > > - " xor %%rcx, %%rcx;" > > + " xor %%ecx, %%ecx;" > > " adoxq 0(%1), %%r8;" > > " mulxq 40(%1), %%r9, %%rbx;" > > " adcx %%r13, %%r9;" > > @@ -607,7 +607,7 @@ static inline void fsqr2(u64 *out, const u64 *f, u64 *tmp) > > asm volatile( > > /* Step 1: Compute all partial products */ > > " movq 0(%1), %%rdx;" /* f[0] */ > > - " mulxq 8(%1), %%r8, %%r14;" " xor %%r15, %%r15;" /* f[1]*f[0] */ > > + " mulxq 8(%1), %%r8, %%r14;" " xor %%r15d, %%r15d;" /* f[1]*f[0] */ > > " 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] */ > > @@ -617,7 +617,7 @@ static inline void fsqr2(u64 *out, const u64 *f, u64 *tmp) > > " mulxq 16(%1), %%rax, %%rcx;" " mov $0, %%r14;" /* f[2]*f[1] */ > > > > /* Step 2: Compute two parallel carry chains */ > > - " xor %%r15, %%r15;" > > + " xor %%r15d, %%r15d;" > > " adox %%rax, %%r10;" > > " adcx %%r8, %%r8;" > > " adox %%rcx, %%r11;" > > @@ -647,7 +647,7 @@ static inline void fsqr2(u64 *out, const u64 *f, u64 *tmp) > > > > /* Step 1: Compute all partial products */ > > " movq 32(%1), %%rdx;" /* f[0] */ > > - " mulxq 40(%1), %%r8, %%r14;" " xor %%r15, %%r15;" /* f[1]*f[0] */ > > + " mulxq 40(%1), %%r8, %%r14;" " xor %%r15d, %%r15d;" /* f[1]*f[0] */ > > " 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] */ > > @@ -657,7 +657,7 @@ static inline void fsqr2(u64 *out, const u64 *f, u64 *tmp) > > " mulxq 48(%1), %%rax, %%rcx;" " mov $0, %%r14;" /* f[2]*f[1] */ > > > > /* Step 2: Compute two parallel carry chains */ > > - " xor %%r15, %%r15;" > > + " xor %%r15d, %%r15d;" > > " adox %%rax, %%r10;" > > " adcx %%r8, %%r8;" > > " adox %%rcx, %%r11;" > > @@ -692,7 +692,7 @@ static inline void fsqr2(u64 *out, const u64 *f, u64 *tmp) > > /* Step 1: Compute dst + carry == tmp_hi * 38 + tmp_lo */ > > " mov $38, %%rdx;" > > " mulxq 32(%1), %%r8, %%r13;" > > - " xor %%rcx, %%rcx;" > > + " xor %%ecx, %%ecx;" > > " adoxq 0(%1), %%r8;" > > " mulxq 40(%1), %%r9, %%rbx;" > > " adcx %%r13, %%r9;" > > @@ -725,7 +725,7 @@ static inline void fsqr2(u64 *out, const u64 *f, u64 *tmp) > > /* Step 1: Compute dst + carry == tmp_hi * 38 + tmp_lo */ > > " mov $38, %%rdx;" > > " mulxq 96(%1), %%r8, %%r13;" > > - " xor %%rcx, %%rcx;" > > + " xor %%ecx, %%ecx;" > > " adoxq 64(%1), %%r8;" > > " mulxq 104(%1), %%r9, %%rbx;" > > " adcx %%r13, %%r9;" > > -- > > 2.26.2 > >
