1 files changed, 142 insertions, 0 deletions
diff --git a/Core/MdePkg/Library/BaseMemoryLibOptDxe/AArch64/CompareMem.S b/Core/MdePkg/Library/BaseMemoryLibOptDxe/AArch64/CompareMem.S
new file mode 100644
index 0000000000..a54de6948b
--- /dev/null
+++ b/Core/MdePkg/Library/BaseMemoryLibOptDxe/AArch64/CompareMem.S
@@ -0,0 +1,142 @@
+//
+// Copyright (c) 2013, Linaro Limited
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are met:
+//     * Redistributions of source code must retain the above copyright
+//       notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above copyright
+//       notice, this list of conditions and the following disclaimer in the
+//       documentation and/or other materials provided with the distribution.
+//     * Neither the name of the Linaro nor the
+//       names of its contributors may be used to endorse or promote products
+//       derived from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+//
+
+// Assumptions:
+//
+// ARMv8-a, AArch64
+//
+
+
+// Parameters and result.
+#define src1      x0
+#define src2      x1
+#define limit     x2
+#define result    x0
+
+// Internal variables.
+#define data1     x3
+#define data1w    w3
+#define data2     x4
+#define data2w    w4
+#define diff      x6
+#define endloop   x7
+#define tmp1      x8
+#define tmp2      x9
+#define pos       x11
+#define limit_wd  x12
+#define mask      x13
+
+    .p2align 6
+ASM_GLOBAL ASM_PFX(InternalMemCompareMem)
+ASM_PFX(InternalMemCompareMem):
+    eor     tmp1, src1, src2
+    tst     tmp1, #7
+    b.ne    .Lmisaligned8
+    ands    tmp1, src1, #7
+    b.ne    .Lmutual_align
+    add     limit_wd, limit, #7
+    lsr     limit_wd, limit_wd, #3
+
+    // Start of performance-critical section  -- one 64B cache line.
+.Lloop_aligned:
+    ldr     data1, [src1], #8
+    ldr     data2, [src2], #8
+.Lstart_realigned:
+    subs    limit_wd, limit_wd, #1
+    eor     diff, data1, data2        // Non-zero if differences found.
+    csinv   endloop, diff, xzr, ne    // Last Dword or differences.
+    cbz     endloop, .Lloop_aligned
+    // End of performance-critical section  -- one 64B cache line.
+
+    // Not reached the limit, must have found a diff.
+    cbnz    limit_wd, .Lnot_limit
+
+    // Limit % 8 == 0 => all bytes significant.
+    ands    limit, limit, #7
+    b.eq    .Lnot_limit
+
+    lsl     limit, limit, #3              // Bits -> bytes.
+    mov     mask, #~0
+    lsl     mask, mask, limit
+    bic     data1, data1, mask
+    bic     data2, data2, mask
+
+    orr     diff, diff, mask
+
+.Lnot_limit:
+    rev     diff, diff
+    rev     data1, data1
+    rev     data2, data2
+
+    // The MS-non-zero bit of DIFF marks either the first bit
+    // that is different, or the end of the significant data.
+    // Shifting left now will bring the critical information into the
+    // top bits.
+    clz     pos, diff
+    lsl     data1, data1, pos
+    lsl     data2, data2, pos
+
+    // But we need to zero-extend (char is unsigned) the value and then
+    // perform a signed 32-bit subtraction.
+    lsr     data1, data1, #56
+    sub     result, data1, data2, lsr #56
+    ret
+
+.Lmutual_align:
+    // Sources are mutually aligned, but are not currently at an
+    // alignment boundary.  Round down the addresses and then mask off
+    // the bytes that precede the start point.
+    bic     src1, src1, #7
+    bic     src2, src2, #7
+    add     limit, limit, tmp1          // Adjust the limit for the extra.
+    lsl     tmp1, tmp1, #3              // Bytes beyond alignment -> bits.
+    ldr     data1, [src1], #8
+    neg     tmp1, tmp1                  // Bits to alignment -64.
+    ldr     data2, [src2], #8
+    mov     tmp2, #~0
+
+    // Little-endian.  Early bytes are at LSB.
+    lsr     tmp2, tmp2, tmp1            // Shift (tmp1 & 63).
+    add     limit_wd, limit, #7
+    orr     data1, data1, tmp2
+    orr     data2, data2, tmp2
+    lsr     limit_wd, limit_wd, #3
+    b       .Lstart_realigned
+
+    .p2align 6
+.Lmisaligned8:
+    sub     limit, limit, #1
+1:
+    // Perhaps we can do better than this.
+    ldrb    data1w, [src1], #1
+    ldrb    data2w, [src2], #1
+    subs    limit, limit, #1
+    ccmp    data1w, data2w, #0, cs      // NZCV = 0b0000.
+    b.eq    1b
+    sub     result, data1, data2
+    ret