[VOL-4291] Rw-core updates for gRPC migration
Change-Id: I8d5a554409115b29318089671ca4e1ab3fa98810
diff --git a/vendor/github.com/golang/snappy/decode_arm64.s b/vendor/github.com/golang/snappy/decode_arm64.s
new file mode 100644
index 0000000..7a3ead1
--- /dev/null
+++ b/vendor/github.com/golang/snappy/decode_arm64.s
@@ -0,0 +1,494 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build !appengine
+// +build gc
+// +build !noasm
+
+#include "textflag.h"
+
+// The asm code generally follows the pure Go code in decode_other.go, except
+// where marked with a "!!!".
+
+// func decode(dst, src []byte) int
+//
+// All local variables fit into registers. The non-zero stack size is only to
+// spill registers and push args when issuing a CALL. The register allocation:
+// - R2 scratch
+// - R3 scratch
+// - R4 length or x
+// - R5 offset
+// - R6 &src[s]
+// - R7 &dst[d]
+// + R8 dst_base
+// + R9 dst_len
+// + R10 dst_base + dst_len
+// + R11 src_base
+// + R12 src_len
+// + R13 src_base + src_len
+// - R14 used by doCopy
+// - R15 used by doCopy
+//
+// The registers R8-R13 (marked with a "+") are set at the start of the
+// function, and after a CALL returns, and are not otherwise modified.
+//
+// The d variable is implicitly R7 - R8, and len(dst)-d is R10 - R7.
+// The s variable is implicitly R6 - R11, and len(src)-s is R13 - R6.
+TEXT ·decode(SB), NOSPLIT, $56-56
+ // Initialize R6, R7 and R8-R13.
+ MOVD dst_base+0(FP), R8
+ MOVD dst_len+8(FP), R9
+ MOVD R8, R7
+ MOVD R8, R10
+ ADD R9, R10, R10
+ MOVD src_base+24(FP), R11
+ MOVD src_len+32(FP), R12
+ MOVD R11, R6
+ MOVD R11, R13
+ ADD R12, R13, R13
+
+loop:
+ // for s < len(src)
+ CMP R13, R6
+ BEQ end
+
+ // R4 = uint32(src[s])
+ //
+ // switch src[s] & 0x03
+ MOVBU (R6), R4
+ MOVW R4, R3
+ ANDW $3, R3
+ MOVW $1, R1
+ CMPW R1, R3
+ BGE tagCopy
+
+ // ----------------------------------------
+ // The code below handles literal tags.
+
+ // case tagLiteral:
+ // x := uint32(src[s] >> 2)
+ // switch
+ MOVW $60, R1
+ LSRW $2, R4, R4
+ CMPW R4, R1
+ BLS tagLit60Plus
+
+ // case x < 60:
+ // s++
+ ADD $1, R6, R6
+
+doLit:
+ // This is the end of the inner "switch", when we have a literal tag.
+ //
+ // We assume that R4 == x and x fits in a uint32, where x is the variable
+ // used in the pure Go decode_other.go code.
+
+ // length = int(x) + 1
+ //
+ // Unlike the pure Go code, we don't need to check if length <= 0 because
+ // R4 can hold 64 bits, so the increment cannot overflow.
+ ADD $1, R4, R4
+
+ // Prepare to check if copying length bytes will run past the end of dst or
+ // src.
+ //
+ // R2 = len(dst) - d
+ // R3 = len(src) - s
+ MOVD R10, R2
+ SUB R7, R2, R2
+ MOVD R13, R3
+ SUB R6, R3, R3
+
+ // !!! Try a faster technique for short (16 or fewer bytes) copies.
+ //
+ // if length > 16 || len(dst)-d < 16 || len(src)-s < 16 {
+ // goto callMemmove // Fall back on calling runtime·memmove.
+ // }
+ //
+ // The C++ snappy code calls this TryFastAppend. It also checks len(src)-s
+ // against 21 instead of 16, because it cannot assume that all of its input
+ // is contiguous in memory and so it needs to leave enough source bytes to
+ // read the next tag without refilling buffers, but Go's Decode assumes
+ // contiguousness (the src argument is a []byte).
+ CMP $16, R4
+ BGT callMemmove
+ CMP $16, R2
+ BLT callMemmove
+ CMP $16, R3
+ BLT callMemmove
+
+ // !!! Implement the copy from src to dst as a 16-byte load and store.
+ // (Decode's documentation says that dst and src must not overlap.)
+ //
+ // This always copies 16 bytes, instead of only length bytes, but that's
+ // OK. If the input is a valid Snappy encoding then subsequent iterations
+ // will fix up the overrun. Otherwise, Decode returns a nil []byte (and a
+ // non-nil error), so the overrun will be ignored.
+ //
+ // Note that on arm64, it is legal and cheap to issue unaligned 8-byte or
+ // 16-byte loads and stores. This technique probably wouldn't be as
+ // effective on architectures that are fussier about alignment.
+ LDP 0(R6), (R14, R15)
+ STP (R14, R15), 0(R7)
+
+ // d += length
+ // s += length
+ ADD R4, R7, R7
+ ADD R4, R6, R6
+ B loop
+
+callMemmove:
+ // if length > len(dst)-d || length > len(src)-s { etc }
+ CMP R2, R4
+ BGT errCorrupt
+ CMP R3, R4
+ BGT errCorrupt
+
+ // copy(dst[d:], src[s:s+length])
+ //
+ // This means calling runtime·memmove(&dst[d], &src[s], length), so we push
+ // R7, R6 and R4 as arguments. Coincidentally, we also need to spill those
+ // three registers to the stack, to save local variables across the CALL.
+ MOVD R7, 8(RSP)
+ MOVD R6, 16(RSP)
+ MOVD R4, 24(RSP)
+ MOVD R7, 32(RSP)
+ MOVD R6, 40(RSP)
+ MOVD R4, 48(RSP)
+ CALL runtime·memmove(SB)
+
+ // Restore local variables: unspill registers from the stack and
+ // re-calculate R8-R13.
+ MOVD 32(RSP), R7
+ MOVD 40(RSP), R6
+ MOVD 48(RSP), R4
+ MOVD dst_base+0(FP), R8
+ MOVD dst_len+8(FP), R9
+ MOVD R8, R10
+ ADD R9, R10, R10
+ MOVD src_base+24(FP), R11
+ MOVD src_len+32(FP), R12
+ MOVD R11, R13
+ ADD R12, R13, R13
+
+ // d += length
+ // s += length
+ ADD R4, R7, R7
+ ADD R4, R6, R6
+ B loop
+
+tagLit60Plus:
+ // !!! This fragment does the
+ //
+ // s += x - 58; if uint(s) > uint(len(src)) { etc }
+ //
+ // checks. In the asm version, we code it once instead of once per switch case.
+ ADD R4, R6, R6
+ SUB $58, R6, R6
+ MOVD R6, R3
+ SUB R11, R3, R3
+ CMP R12, R3
+ BGT errCorrupt
+
+ // case x == 60:
+ MOVW $61, R1
+ CMPW R1, R4
+ BEQ tagLit61
+ BGT tagLit62Plus
+
+ // x = uint32(src[s-1])
+ MOVBU -1(R6), R4
+ B doLit
+
+tagLit61:
+ // case x == 61:
+ // x = uint32(src[s-2]) | uint32(src[s-1])<<8
+ MOVHU -2(R6), R4
+ B doLit
+
+tagLit62Plus:
+ CMPW $62, R4
+ BHI tagLit63
+
+ // case x == 62:
+ // x = uint32(src[s-3]) | uint32(src[s-2])<<8 | uint32(src[s-1])<<16
+ MOVHU -3(R6), R4
+ MOVBU -1(R6), R3
+ ORR R3<<16, R4
+ B doLit
+
+tagLit63:
+ // case x == 63:
+ // x = uint32(src[s-4]) | uint32(src[s-3])<<8 | uint32(src[s-2])<<16 | uint32(src[s-1])<<24
+ MOVWU -4(R6), R4
+ B doLit
+
+ // The code above handles literal tags.
+ // ----------------------------------------
+ // The code below handles copy tags.
+
+tagCopy4:
+ // case tagCopy4:
+ // s += 5
+ ADD $5, R6, R6
+
+ // if uint(s) > uint(len(src)) { etc }
+ MOVD R6, R3
+ SUB R11, R3, R3
+ CMP R12, R3
+ BGT errCorrupt
+
+ // length = 1 + int(src[s-5])>>2
+ MOVD $1, R1
+ ADD R4>>2, R1, R4
+
+ // offset = int(uint32(src[s-4]) | uint32(src[s-3])<<8 | uint32(src[s-2])<<16 | uint32(src[s-1])<<24)
+ MOVWU -4(R6), R5
+ B doCopy
+
+tagCopy2:
+ // case tagCopy2:
+ // s += 3
+ ADD $3, R6, R6
+
+ // if uint(s) > uint(len(src)) { etc }
+ MOVD R6, R3
+ SUB R11, R3, R3
+ CMP R12, R3
+ BGT errCorrupt
+
+ // length = 1 + int(src[s-3])>>2
+ MOVD $1, R1
+ ADD R4>>2, R1, R4
+
+ // offset = int(uint32(src[s-2]) | uint32(src[s-1])<<8)
+ MOVHU -2(R6), R5
+ B doCopy
+
+tagCopy:
+ // We have a copy tag. We assume that:
+ // - R3 == src[s] & 0x03
+ // - R4 == src[s]
+ CMP $2, R3
+ BEQ tagCopy2
+ BGT tagCopy4
+
+ // case tagCopy1:
+ // s += 2
+ ADD $2, R6, R6
+
+ // if uint(s) > uint(len(src)) { etc }
+ MOVD R6, R3
+ SUB R11, R3, R3
+ CMP R12, R3
+ BGT errCorrupt
+
+ // offset = int(uint32(src[s-2])&0xe0<<3 | uint32(src[s-1]))
+ MOVD R4, R5
+ AND $0xe0, R5
+ MOVBU -1(R6), R3
+ ORR R5<<3, R3, R5
+
+ // length = 4 + int(src[s-2])>>2&0x7
+ MOVD $7, R1
+ AND R4>>2, R1, R4
+ ADD $4, R4, R4
+
+doCopy:
+ // This is the end of the outer "switch", when we have a copy tag.
+ //
+ // We assume that:
+ // - R4 == length && R4 > 0
+ // - R5 == offset
+
+ // if offset <= 0 { etc }
+ MOVD $0, R1
+ CMP R1, R5
+ BLE errCorrupt
+
+ // if d < offset { etc }
+ MOVD R7, R3
+ SUB R8, R3, R3
+ CMP R5, R3
+ BLT errCorrupt
+
+ // if length > len(dst)-d { etc }
+ MOVD R10, R3
+ SUB R7, R3, R3
+ CMP R3, R4
+ BGT errCorrupt
+
+ // forwardCopy(dst[d:d+length], dst[d-offset:]); d += length
+ //
+ // Set:
+ // - R14 = len(dst)-d
+ // - R15 = &dst[d-offset]
+ MOVD R10, R14
+ SUB R7, R14, R14
+ MOVD R7, R15
+ SUB R5, R15, R15
+
+ // !!! Try a faster technique for short (16 or fewer bytes) forward copies.
+ //
+ // First, try using two 8-byte load/stores, similar to the doLit technique
+ // above. Even if dst[d:d+length] and dst[d-offset:] can overlap, this is
+ // still OK if offset >= 8. Note that this has to be two 8-byte load/stores
+ // and not one 16-byte load/store, and the first store has to be before the
+ // second load, due to the overlap if offset is in the range [8, 16).
+ //
+ // if length > 16 || offset < 8 || len(dst)-d < 16 {
+ // goto slowForwardCopy
+ // }
+ // copy 16 bytes
+ // d += length
+ CMP $16, R4
+ BGT slowForwardCopy
+ CMP $8, R5
+ BLT slowForwardCopy
+ CMP $16, R14
+ BLT slowForwardCopy
+ MOVD 0(R15), R2
+ MOVD R2, 0(R7)
+ MOVD 8(R15), R3
+ MOVD R3, 8(R7)
+ ADD R4, R7, R7
+ B loop
+
+slowForwardCopy:
+ // !!! If the forward copy is longer than 16 bytes, or if offset < 8, we
+ // can still try 8-byte load stores, provided we can overrun up to 10 extra
+ // bytes. As above, the overrun will be fixed up by subsequent iterations
+ // of the outermost loop.
+ //
+ // The C++ snappy code calls this technique IncrementalCopyFastPath. Its
+ // commentary says:
+ //
+ // ----
+ //
+ // The main part of this loop is a simple copy of eight bytes at a time
+ // until we've copied (at least) the requested amount of bytes. However,
+ // if d and d-offset are less than eight bytes apart (indicating a
+ // repeating pattern of length < 8), we first need to expand the pattern in
+ // order to get the correct results. For instance, if the buffer looks like
+ // this, with the eight-byte <d-offset> and <d> patterns marked as
+ // intervals:
+ //
+ // abxxxxxxxxxxxx
+ // [------] d-offset
+ // [------] d
+ //
+ // a single eight-byte copy from <d-offset> to <d> will repeat the pattern
+ // once, after which we can move <d> two bytes without moving <d-offset>:
+ //
+ // ababxxxxxxxxxx
+ // [------] d-offset
+ // [------] d
+ //
+ // and repeat the exercise until the two no longer overlap.
+ //
+ // This allows us to do very well in the special case of one single byte
+ // repeated many times, without taking a big hit for more general cases.
+ //
+ // The worst case of extra writing past the end of the match occurs when
+ // offset == 1 and length == 1; the last copy will read from byte positions
+ // [0..7] and write to [4..11], whereas it was only supposed to write to
+ // position 1. Thus, ten excess bytes.
+ //
+ // ----
+ //
+ // That "10 byte overrun" worst case is confirmed by Go's
+ // TestSlowForwardCopyOverrun, which also tests the fixUpSlowForwardCopy
+ // and finishSlowForwardCopy algorithm.
+ //
+ // if length > len(dst)-d-10 {
+ // goto verySlowForwardCopy
+ // }
+ SUB $10, R14, R14
+ CMP R14, R4
+ BGT verySlowForwardCopy
+
+makeOffsetAtLeast8:
+ // !!! As above, expand the pattern so that offset >= 8 and we can use
+ // 8-byte load/stores.
+ //
+ // for offset < 8 {
+ // copy 8 bytes from dst[d-offset:] to dst[d:]
+ // length -= offset
+ // d += offset
+ // offset += offset
+ // // The two previous lines together means that d-offset, and therefore
+ // // R15, is unchanged.
+ // }
+ CMP $8, R5
+ BGE fixUpSlowForwardCopy
+ MOVD (R15), R3
+ MOVD R3, (R7)
+ SUB R5, R4, R4
+ ADD R5, R7, R7
+ ADD R5, R5, R5
+ B makeOffsetAtLeast8
+
+fixUpSlowForwardCopy:
+ // !!! Add length (which might be negative now) to d (implied by R7 being
+ // &dst[d]) so that d ends up at the right place when we jump back to the
+ // top of the loop. Before we do that, though, we save R7 to R2 so that, if
+ // length is positive, copying the remaining length bytes will write to the
+ // right place.
+ MOVD R7, R2
+ ADD R4, R7, R7
+
+finishSlowForwardCopy:
+ // !!! Repeat 8-byte load/stores until length <= 0. Ending with a negative
+ // length means that we overrun, but as above, that will be fixed up by
+ // subsequent iterations of the outermost loop.
+ MOVD $0, R1
+ CMP R1, R4
+ BLE loop
+ MOVD (R15), R3
+ MOVD R3, (R2)
+ ADD $8, R15, R15
+ ADD $8, R2, R2
+ SUB $8, R4, R4
+ B finishSlowForwardCopy
+
+verySlowForwardCopy:
+ // verySlowForwardCopy is a simple implementation of forward copy. In C
+ // parlance, this is a do/while loop instead of a while loop, since we know
+ // that length > 0. In Go syntax:
+ //
+ // for {
+ // dst[d] = dst[d - offset]
+ // d++
+ // length--
+ // if length == 0 {
+ // break
+ // }
+ // }
+ MOVB (R15), R3
+ MOVB R3, (R7)
+ ADD $1, R15, R15
+ ADD $1, R7, R7
+ SUB $1, R4, R4
+ CBNZ R4, verySlowForwardCopy
+ B loop
+
+ // The code above handles copy tags.
+ // ----------------------------------------
+
+end:
+ // This is the end of the "for s < len(src)".
+ //
+ // if d != len(dst) { etc }
+ CMP R10, R7
+ BNE errCorrupt
+
+ // return 0
+ MOVD $0, ret+48(FP)
+ RET
+
+errCorrupt:
+ // return decodeErrCodeCorrupt
+ MOVD $1, R2
+ MOVD R2, ret+48(FP)
+ RET