[PATCH v2] crypto/x86: Use CRC32 mnemonic in crc32c-intel_glue.c

* [PATCH v2] crypto/x86: Use CRC32 mnemonic in crc32c-intel_glue.c
@ 2020-08-05 11:17 Uros Bizjak
  2020-08-21  7:57 ` Herbert Xu
  0 siblings, 1 reply; 2+ messages in thread
From: Uros Bizjak @ 2020-08-05 11:17 UTC (permalink / raw)
  To: linux-crypto, x86, linux-kernel
  Cc: Uros Bizjak, Herbert Xu, David S. Miller, Thomas Gleixner,
	Ingo Molnar, Borislav Petkov, H. Peter Anvin

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>
---
 arch/x86/crypto/crc32c-intel_glue.c | 18 ++++++------------
 1 file changed, 6 insertions(+), 12 deletions(-)

diff --git a/arch/x86/crypto/crc32c-intel_glue.c b/arch/x86/crypto/crc32c-intel_glue.c
index d2d069bd459b..feccb5254c7e 100644
--- a/arch/x86/crypto/crc32c-intel_glue.c
+++ b/arch/x86/crypto/crc32c-intel_glue.c
@@ -28,9 +28,9 @@
 #define SCALE_F	sizeof(unsigned long)
 
 #ifdef CONFIG_X86_64
-#define REX_PRE "0x48, "
+#define CRC32_INST "crc32q %1, %q0"
 #else
-#define REX_PRE
+#define CRC32_INST "crc32l %1, %0"
 #endif
 
 #ifdef CONFIG_X86_64
@@ -48,11 +48,8 @@ asmlinkage unsigned int crc_pcl(const u8 *buffer, int len,
 static u32 crc32c_intel_le_hw_byte(u32 crc, unsigned char const *data, size_t length)
 {
 	while (length--) {
-		__asm__ __volatile__(
-			".byte 0xf2, 0xf, 0x38, 0xf0, 0xf1"
-			:"=S"(crc)
-			:"0"(crc), "c"(*data)
-		);
+		asm("crc32b %1, %0"
+		    : "+r" (crc) : "rm" (*data));
 		data++;
 	}
 
@@ -66,11 +63,8 @@ static u32 __pure crc32c_intel_le_hw(u32 crc, unsigned char const *p, size_t len
 	unsigned long *ptmp = (unsigned long *)p;
 
 	while (iquotient--) {
-		__asm__ __volatile__(
-			".byte 0xf2, " REX_PRE "0xf, 0x38, 0xf1, 0xf1;"
-			:"=S"(crc)
-			:"0"(crc), "c"(*ptmp)
-		);
+		asm(CRC32_INST
+		    : "+r" (crc) : "rm" (*ptmp));
 		ptmp++;
 	}
 
-- 
2.26.2


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