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3a95887e27
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@gmail.com> CC: Herbert Xu <herbert@gondor.apana.org.au> CC: "David S. Miller" <davem@davemloft.net> CC: Thomas Gleixner <tglx@linutronix.de> CC: Ingo Molnar <mingo@redhat.com> CC: Borislav Petkov <bp@alien8.de> CC: "H. Peter Anvin" <hpa@zytor.com> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au> |
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Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.