License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
-#ifndef MEMCMP
-# define MEMCMP __memcmpeq_avx2
-#endif
+#if IS_IN (libc)
+
+/* __memcmpeq is implemented as:
+ 1. Use ymm vector compares when possible. The only case where
+ vector compares is not possible for when size < VEC_SIZE
+ and loading from either s1 or s2 would cause a page cross.
+ 2. Use xmm vector compare when size >= 8 bytes.
+ 3. Optimistically compare up to first 4 * VEC_SIZE one at a
+ to check for early mismatches. Only do this if its guranteed the
+ work is not wasted.
+ 4. If size is 8 * VEC_SIZE or less, unroll the loop.
+ 5. Compare 4 * VEC_SIZE at a time with the aligned first memory
+ area.
+ 6. Use 2 vector compares when size is 2 * VEC_SIZE or less.
+ 7. Use 4 vector compares when size is 4 * VEC_SIZE or less.
+ 8. Use 8 vector compares when size is 8 * VEC_SIZE or less. */
+
+# include <sysdep.h>
+
+# ifndef MEMCMPEQ
+# define MEMCMPEQ __memcmpeq_avx2
+# endif
+
+# define VPCMPEQ vpcmpeqb
+
+# ifndef VZEROUPPER
+# define VZEROUPPER vzeroupper
+# endif
+
+# ifndef SECTION
+# define SECTION(p) p##.avx
+# endif
+
+# define VEC_SIZE 32
+# define PAGE_SIZE 4096
+
+ .section SECTION(.text), "ax", @progbits
+ENTRY_P2ALIGN (MEMCMPEQ, 6)
+# ifdef __ILP32__
+ /* Clear the upper 32 bits. */
+ movl %edx, %edx
+# endif
+ cmp $VEC_SIZE, %RDX_LP
+ jb L(less_vec)
+
+ /* From VEC to 2 * VEC. No branch when size == VEC_SIZE. */
+ vmovdqu (%rsi), %ymm1
+ VPCMPEQ (%rdi), %ymm1, %ymm1
+ vpmovmskb %ymm1, %eax
+ incl %eax
+ jnz L(return_neq0)
+ cmpq $(VEC_SIZE * 2), %rdx
+ jbe L(last_1x_vec)
+
+ /* Check second VEC no matter what. */
+ vmovdqu VEC_SIZE(%rsi), %ymm2
+ VPCMPEQ VEC_SIZE(%rdi), %ymm2, %ymm2
+ vpmovmskb %ymm2, %eax
+ /* If all 4 VEC where equal eax will be all 1s so incl will overflow
+ and set zero flag. */
+ incl %eax
+ jnz L(return_neq0)
+
+ /* Less than 4 * VEC. */
+ cmpq $(VEC_SIZE * 4), %rdx
+ jbe L(last_2x_vec)
+
+ /* Check third and fourth VEC no matter what. */
+ vmovdqu (VEC_SIZE * 2)(%rsi), %ymm3
+ VPCMPEQ (VEC_SIZE * 2)(%rdi), %ymm3, %ymm3
+ vpmovmskb %ymm3, %eax
+ incl %eax
+ jnz L(return_neq0)
+
+ vmovdqu (VEC_SIZE * 3)(%rsi), %ymm4
+ VPCMPEQ (VEC_SIZE * 3)(%rdi), %ymm4, %ymm4
+ vpmovmskb %ymm4, %eax
+ incl %eax
+ jnz L(return_neq0)
+
+ /* Go to 4x VEC loop. */
+ cmpq $(VEC_SIZE * 8), %rdx
+ ja L(more_8x_vec)
+
+ /* Handle remainder of size = 4 * VEC + 1 to 8 * VEC without any
+ branches. */
+
+ /* Adjust rsi and rdi to avoid indexed address mode. This end up
+ saving a 16 bytes of code, prevents unlamination, and bottlenecks in
+ the AGU. */
+ addq %rdx, %rsi
+ vmovdqu -(VEC_SIZE * 4)(%rsi), %ymm1
+ vmovdqu -(VEC_SIZE * 3)(%rsi), %ymm2
+ addq %rdx, %rdi
+
+ VPCMPEQ -(VEC_SIZE * 4)(%rdi), %ymm1, %ymm1
+ VPCMPEQ -(VEC_SIZE * 3)(%rdi), %ymm2, %ymm2
+
+ vmovdqu -(VEC_SIZE * 2)(%rsi), %ymm3
+ VPCMPEQ -(VEC_SIZE * 2)(%rdi), %ymm3, %ymm3
+ vmovdqu -VEC_SIZE(%rsi), %ymm4
+ VPCMPEQ -VEC_SIZE(%rdi), %ymm4, %ymm4
+
+ /* Reduce VEC0 - VEC4. */
+ vpand %ymm1, %ymm2, %ymm2
+ vpand %ymm3, %ymm4, %ymm4
+ vpand %ymm2, %ymm4, %ymm4
+ vpmovmskb %ymm4, %eax
+ incl %eax
+L(return_neq0):
+L(return_vzeroupper):
+ ZERO_UPPER_VEC_REGISTERS_RETURN
-#include "memcmp-avx2-movbe.S"
+ /* NB: p2align 5 here will ensure the L(loop_4x_vec) is also 32 byte
+ aligned. */
+ .p2align 5
+L(less_vec):
+ /* Check if one or less char. This is necessary for size = 0 but is
+ also faster for size = 1. */
+ cmpl $1, %edx
+ jbe L(one_or_less)
+
+ /* Check if loading one VEC from either s1 or s2 could cause a page
+ cross. This can have false positives but is by far the fastest
+ method. */
+ movl %edi, %eax
+ orl %esi, %eax
+ andl $(PAGE_SIZE - 1), %eax
+ cmpl $(PAGE_SIZE - VEC_SIZE), %eax
+ jg L(page_cross_less_vec)
+
+ /* No page cross possible. */
+ vmovdqu (%rsi), %ymm2
+ VPCMPEQ (%rdi), %ymm2, %ymm2
+ vpmovmskb %ymm2, %eax
+ incl %eax
+ /* Result will be zero if s1 and s2 match. Otherwise first set bit
+ will be first mismatch. */
+ bzhil %edx, %eax, %eax
+ VZEROUPPER_RETURN
+
+ /* Relatively cold but placing close to L(less_vec) for 2 byte jump
+ encoding. */
+ .p2align 4
+L(one_or_less):
+ jb L(zero)
+ movzbl (%rsi), %ecx
+ movzbl (%rdi), %eax
+ subl %ecx, %eax
+ /* No ymm register was touched. */
+ ret
+ /* Within the same 16 byte block is L(one_or_less). */
+L(zero):
+ xorl %eax, %eax
+ ret
+
+ .p2align 4
+L(last_1x_vec):
+ vmovdqu -(VEC_SIZE * 1)(%rsi, %rdx), %ymm1
+ VPCMPEQ -(VEC_SIZE * 1)(%rdi, %rdx), %ymm1, %ymm1
+ vpmovmskb %ymm1, %eax
+ incl %eax
+ VZEROUPPER_RETURN
+
+ .p2align 4
+L(last_2x_vec):
+ vmovdqu -(VEC_SIZE * 2)(%rsi, %rdx), %ymm1
+ VPCMPEQ -(VEC_SIZE * 2)(%rdi, %rdx), %ymm1, %ymm1
+ vmovdqu -(VEC_SIZE * 1)(%rsi, %rdx), %ymm2
+ VPCMPEQ -(VEC_SIZE * 1)(%rdi, %rdx), %ymm2, %ymm2
+ vpand %ymm1, %ymm2, %ymm2
+ vpmovmskb %ymm2, %eax
+ incl %eax
+ VZEROUPPER_RETURN
+
+ .p2align 4
+L(more_8x_vec):
+ /* Set end of s1 in rdx. */
+ leaq -(VEC_SIZE * 4)(%rdi, %rdx), %rdx
+ /* rsi stores s2 - s1. This allows loop to only update one pointer.
+ */
+ subq %rdi, %rsi
+ /* Align s1 pointer. */
+ andq $-VEC_SIZE, %rdi
+ /* Adjust because first 4x vec where check already. */
+ subq $-(VEC_SIZE * 4), %rdi
+ .p2align 4
+L(loop_4x_vec):
+ /* rsi has s2 - s1 so get correct address by adding s1 (in rdi). */
+ vmovdqu (%rsi, %rdi), %ymm1
+ VPCMPEQ (%rdi), %ymm1, %ymm1
+
+ vmovdqu VEC_SIZE(%rsi, %rdi), %ymm2
+ VPCMPEQ VEC_SIZE(%rdi), %ymm2, %ymm2
+
+ vmovdqu (VEC_SIZE * 2)(%rsi, %rdi), %ymm3
+ VPCMPEQ (VEC_SIZE * 2)(%rdi), %ymm3, %ymm3
+
+ vmovdqu (VEC_SIZE * 3)(%rsi, %rdi), %ymm4
+ VPCMPEQ (VEC_SIZE * 3)(%rdi), %ymm4, %ymm4
+
+ vpand %ymm1, %ymm2, %ymm2
+ vpand %ymm3, %ymm4, %ymm4
+ vpand %ymm2, %ymm4, %ymm4
+ vpmovmskb %ymm4, %eax
+ incl %eax
+ jnz L(return_neq1)
+ subq $-(VEC_SIZE * 4), %rdi
+ /* Check if s1 pointer at end. */
+ cmpq %rdx, %rdi
+ jb L(loop_4x_vec)
+
+ vmovdqu (VEC_SIZE * 3)(%rsi, %rdx), %ymm4
+ VPCMPEQ (VEC_SIZE * 3)(%rdx), %ymm4, %ymm4
+ subq %rdx, %rdi
+ /* rdi has 4 * VEC_SIZE - remaining length. */
+ cmpl $(VEC_SIZE * 3), %edi
+ jae L(8x_last_1x_vec)
+ /* Load regardless of branch. */
+ vmovdqu (VEC_SIZE * 2)(%rsi, %rdx), %ymm3
+ VPCMPEQ (VEC_SIZE * 2)(%rdx), %ymm3, %ymm3
+ cmpl $(VEC_SIZE * 2), %edi
+ jae L(8x_last_2x_vec)
+ /* Check last 4 VEC. */
+ vmovdqu VEC_SIZE(%rsi, %rdx), %ymm1
+ VPCMPEQ VEC_SIZE(%rdx), %ymm1, %ymm1
+
+ vmovdqu (%rsi, %rdx), %ymm2
+ VPCMPEQ (%rdx), %ymm2, %ymm2
+
+ vpand %ymm3, %ymm4, %ymm4
+ vpand %ymm1, %ymm2, %ymm3
+L(8x_last_2x_vec):
+ vpand %ymm3, %ymm4, %ymm4
+L(8x_last_1x_vec):
+ vpmovmskb %ymm4, %eax
+ /* Restore s1 pointer to rdi. */
+ incl %eax
+L(return_neq1):
+ VZEROUPPER_RETURN
+
+ /* Relatively cold case as page cross are unexpected. */
+ .p2align 4
+L(page_cross_less_vec):
+ cmpl $16, %edx
+ jae L(between_16_31)
+ cmpl $8, %edx
+ ja L(between_9_15)
+ cmpl $4, %edx
+ jb L(between_2_3)
+ /* From 4 to 8 bytes. No branch when size == 4. */
+ movl (%rdi), %eax
+ subl (%rsi), %eax
+ movl -4(%rdi, %rdx), %ecx
+ movl -4(%rsi, %rdx), %edi
+ subl %edi, %ecx
+ orl %ecx, %eax
+ ret
+
+ .p2align 4,, 8
+L(between_16_31):
+ /* From 16 to 31 bytes. No branch when size == 16. */
+
+ /* Safe to use xmm[0, 15] as no vzeroupper is needed so RTM safe.
+ */
+ vmovdqu (%rsi), %xmm1
+ vpcmpeqb (%rdi), %xmm1, %xmm1
+ vmovdqu -16(%rsi, %rdx), %xmm2
+ vpcmpeqb -16(%rdi, %rdx), %xmm2, %xmm2
+ vpand %xmm1, %xmm2, %xmm2
+ vpmovmskb %xmm2, %eax
+ notw %ax
+ /* No ymm register was touched. */
+ ret
+
+ .p2align 4,, 8
+L(between_9_15):
+ /* From 9 to 15 bytes. */
+ movq (%rdi), %rax
+ subq (%rsi), %rax
+ movq -8(%rdi, %rdx), %rcx
+ movq -8(%rsi, %rdx), %rdi
+ subq %rdi, %rcx
+ orq %rcx, %rax
+ /* edx is guranteed to be a non-zero int. */
+ cmovnz %edx, %eax
+ ret
+
+ /* Don't align. This is cold and aligning here will cause code
+ to spill into next cache line. */
+L(between_2_3):
+ /* From 2 to 3 bytes. No branch when size == 2. */
+ movzwl (%rdi), %eax
+ movzwl (%rsi), %ecx
+ subl %ecx, %eax
+ movzbl -1(%rdi, %rdx), %ecx
+ /* All machines that support evex will insert a "merging uop"
+ avoiding any serious partial register stalls. */
+ subb -1(%rsi, %rdx), %cl
+ orl %ecx, %eax
+ /* No ymm register was touched. */
+ ret
+
+ /* 2 Bytes from next cache line. */
+END (MEMCMPEQ)
+#endif
projects / thirdparty / glibc.git / commitdiff
