On Wed, Aug 05, 2020 at 01:17:29PM +0200, Uros Bizjak wrote: > Current minimum required version of binutils is 2.23, > which supports CRC32 instruction mnemonic. > > Replace the byte-wise specification of CRC32 with this proper mnemonic. > The compiler is now able to pass memory operand to the instruction, > so there is no need for a temporary register anymore. > > Some examples of the improvement: > > 12a: 48 8b 08 mov (%rax),%rcx > 12d: f2 48 0f 38 f1 f1 crc32q %rcx,%rsi > 133: 48 83 c0 08 add $0x8,%rax > 137: 48 39 d0 cmp %rdx,%rax > 13a: 75 ee jne 12a <crc32c_intel_update+0x1a> > > to: > > 125: f2 48 0f 38 f1 06 crc32q (%rsi),%rax > 12b: 48 83 c6 08 add $0x8,%rsi > 12f: 48 39 d6 cmp %rdx,%rsi > 132: 75 f1 jne 125 <crc32c_intel_update+0x15> > > and: > > 146: 0f b6 08 movzbl (%rax),%ecx > 149: f2 0f 38 f0 f1 crc32b %cl,%esi > 14e: 48 83 c0 01 add $0x1,%rax > 152: 48 39 d0 cmp %rdx,%rax > 155: 75 ef jne 146 <crc32c_intel_update+0x36> > > to: > > 13b: f2 0f 38 f0 02 crc32b (%rdx),%eax > 140: 48 83 c2 01 add $0x1,%rdx > 144: 48 39 ca cmp %rcx,%rdx > 147: 75 f2 jne 13b <crc32c_intel_update+0x2b> > > As the compiler has some more freedom w.r.t. register allocation, > there is also a couple of reg-reg moves removed. > > There are no hidden states for CRC32 insn, so there is no need to mark > assembly as volatile. > > v2: Introduce CRC32_INST define. > > Signed-off-by: Uros Bizjak <ubizjak@xxxxxxxxx> > CC: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx> > CC: "David S. Miller" <davem@xxxxxxxxxxxxx> > CC: Thomas Gleixner <tglx@xxxxxxxxxxxxx> > CC: Ingo Molnar <mingo@xxxxxxxxxx> > CC: Borislav Petkov <bp@xxxxxxxxx> > CC: "H. Peter Anvin" <hpa@xxxxxxxxx> > --- > arch/x86/crypto/crc32c-intel_glue.c | 18 ++++++------------ > 1 file changed, 6 insertions(+), 12 deletions(-) Patch applied. Thanks. -- Email: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx> Home Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
