From 404aeae4545d2426c089a5f8d5e82dae56f5212b Mon Sep 17 00:00:00 2001
From: Rutger Broekhoff
Date: Fri, 29 Dec 2023 21:31:53 +0100
Subject: Make Nix builds work

---
 .../klauspost/compress/s2/decode_arm64.s           | 574 +++++++++++++++++++++
 1 file changed, 574 insertions(+)
 create mode 100644 vendor/github.com/klauspost/compress/s2/decode_arm64.s

(limited to 'vendor/github.com/klauspost/compress/s2/decode_arm64.s')

diff --git a/vendor/github.com/klauspost/compress/s2/decode_arm64.s b/vendor/github.com/klauspost/compress/s2/decode_arm64.s
new file mode 100644
index 0000000..4b63d50
--- /dev/null
+++ b/vendor/github.com/klauspost/compress/s2/decode_arm64.s
@@ -0,0 +1,574 @@
+// 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"
+
+#define R_TMP0 R2
+#define R_TMP1 R3
+#define R_LEN R4
+#define R_OFF R5
+#define R_SRC R6
+#define R_DST R7
+#define R_DBASE R8
+#define R_DLEN R9
+#define R_DEND R10
+#define R_SBASE R11
+#define R_SLEN R12
+#define R_SEND R13
+#define R_TMP2 R14
+#define R_TMP3 R15
+
+// TEST_SRC will check if R_SRC is <= SRC_END
+#define TEST_SRC() \
+	CMP R_SEND, R_SRC \
+	BGT errCorrupt
+
+// MOVD R_SRC, R_TMP1
+// SUB  R_SBASE, R_TMP1, R_TMP1
+// CMP  R_SLEN, R_TMP1
+// BGT  errCorrupt
+
+// 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:
+//	- R_TMP0	scratch
+//	- R_TMP1	scratch
+//	- R_LEN	length or x
+//	- R_OFF	offset
+//	- R_SRC	&src[s]
+//	- R_DST	&dst[d]
+//	+ R_DBASE	dst_base
+//	+ R_DLEN	dst_len
+//	+ R_DEND	dst_base + dst_len
+//	+ R_SBASE	src_base
+//	+ R_SLEN	src_len
+//	+ R_SEND	src_base + src_len
+//	- R_TMP2	used by doCopy
+//	- R_TMP3	used by doCopy
+//
+// The registers R_DBASE-R_SEND (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 R_DST - R_DBASE,  and len(dst)-d is R_DEND - R_DST.
+// The s variable is implicitly R_SRC - R_SBASE, and len(src)-s is R_SEND - R_SRC.
+TEXT ·s2Decode(SB), NOSPLIT, $56-64
+	// Initialize R_SRC, R_DST and R_DBASE-R_SEND.
+	MOVD dst_base+0(FP), R_DBASE
+	MOVD dst_len+8(FP), R_DLEN
+	MOVD R_DBASE, R_DST
+	MOVD R_DBASE, R_DEND
+	ADD  R_DLEN, R_DEND, R_DEND
+	MOVD src_base+24(FP), R_SBASE
+	MOVD src_len+32(FP), R_SLEN
+	MOVD R_SBASE, R_SRC
+	MOVD R_SBASE, R_SEND
+	ADD  R_SLEN, R_SEND, R_SEND
+	MOVD $0, R_OFF
+
+loop:
+	// for s < len(src)
+	CMP R_SEND, R_SRC
+	BEQ end
+
+	// R_LEN = uint32(src[s])
+	//
+	// switch src[s] & 0x03
+	MOVBU (R_SRC), R_LEN
+	MOVW  R_LEN, R_TMP1
+	ANDW  $3, R_TMP1
+	MOVW  $1, R1
+	CMPW  R1, R_TMP1
+	BGE   tagCopy
+
+	// ----------------------------------------
+	// The code below handles literal tags.
+
+	// case tagLiteral:
+	// x := uint32(src[s] >> 2)
+	// switch
+	MOVW $60, R1
+	LSRW $2, R_LEN, R_LEN
+	CMPW R_LEN, R1
+	BLS  tagLit60Plus
+
+	// case x < 60:
+	// s++
+	ADD $1, R_SRC, R_SRC
+
+doLit:
+	// This is the end of the inner "switch", when we have a literal tag.
+	//
+	// We assume that R_LEN == 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
+	// R_LEN can hold 64 bits, so the increment cannot overflow.
+	ADD $1, R_LEN, R_LEN
+
+	// Prepare to check if copying length bytes will run past the end of dst or
+	// src.
+	//
+	// R_TMP0 = len(dst) - d
+	// R_TMP1 = len(src) - s
+	MOVD R_DEND, R_TMP0
+	SUB  R_DST, R_TMP0, R_TMP0
+	MOVD R_SEND, R_TMP1
+	SUB  R_SRC, R_TMP1, R_TMP1
+
+	// !!! 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, R_LEN
+	BGT callMemmove
+	CMP $16, R_TMP0
+	BLT callMemmove
+	CMP $16, R_TMP1
+	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(R_SRC), (R_TMP2, R_TMP3)
+	STP (R_TMP2, R_TMP3), 0(R_DST)
+
+	// d += length
+	// s += length
+	ADD R_LEN, R_DST, R_DST
+	ADD R_LEN, R_SRC, R_SRC
+	B   loop
+
+callMemmove:
+	// if length > len(dst)-d || length > len(src)-s { etc }
+	CMP R_TMP0, R_LEN
+	BGT errCorrupt
+	CMP R_TMP1, R_LEN
+	BGT errCorrupt
+
+	// copy(dst[d:], src[s:s+length])
+	//
+	// This means calling runtime·memmove(&dst[d], &src[s], length), so we push
+	// R_DST, R_SRC and R_LEN as arguments. Coincidentally, we also need to spill those
+	// three registers to the stack, to save local variables across the CALL.
+	MOVD R_DST, 8(RSP)
+	MOVD R_SRC, 16(RSP)
+	MOVD R_LEN, 24(RSP)
+	MOVD R_DST, 32(RSP)
+	MOVD R_SRC, 40(RSP)
+	MOVD R_LEN, 48(RSP)
+	MOVD R_OFF, 56(RSP)
+	CALL runtime·memmove(SB)
+
+	// Restore local variables: unspill registers from the stack and
+	// re-calculate R_DBASE-R_SEND.
+	MOVD 32(RSP), R_DST
+	MOVD 40(RSP), R_SRC
+	MOVD 48(RSP), R_LEN
+	MOVD 56(RSP), R_OFF
+	MOVD dst_base+0(FP), R_DBASE
+	MOVD dst_len+8(FP), R_DLEN
+	MOVD R_DBASE, R_DEND
+	ADD  R_DLEN, R_DEND, R_DEND
+	MOVD src_base+24(FP), R_SBASE
+	MOVD src_len+32(FP), R_SLEN
+	MOVD R_SBASE, R_SEND
+	ADD  R_SLEN, R_SEND, R_SEND
+
+	// d += length
+	// s += length
+	ADD R_LEN, R_DST, R_DST
+	ADD R_LEN, R_SRC, R_SRC
+	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 R_LEN, R_SRC, R_SRC
+	SUB $58, R_SRC, R_SRC
+	TEST_SRC()
+
+	// case x == 60:
+	MOVW $61, R1
+	CMPW R1, R_LEN
+	BEQ  tagLit61
+	BGT  tagLit62Plus
+
+	// x = uint32(src[s-1])
+	MOVBU -1(R_SRC), R_LEN
+	B     doLit
+
+tagLit61:
+	// case x == 61:
+	// x = uint32(src[s-2]) | uint32(src[s-1])<<8
+	MOVHU -2(R_SRC), R_LEN
+	B     doLit
+
+tagLit62Plus:
+	CMPW $62, R_LEN
+	BHI  tagLit63
+
+	// case x == 62:
+	// x = uint32(src[s-3]) | uint32(src[s-2])<<8 | uint32(src[s-1])<<16
+	MOVHU -3(R_SRC), R_LEN
+	MOVBU -1(R_SRC), R_TMP1
+	ORR   R_TMP1<<16, R_LEN
+	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(R_SRC), R_LEN
+	B     doLit
+
+	// The code above handles literal tags.
+	// ----------------------------------------
+	// The code below handles copy tags.
+
+tagCopy4:
+	// case tagCopy4:
+	// s += 5
+	ADD $5, R_SRC, R_SRC
+
+	// if uint(s) > uint(len(src)) { etc }
+	MOVD R_SRC, R_TMP1
+	SUB  R_SBASE, R_TMP1, R_TMP1
+	CMP  R_SLEN, R_TMP1
+	BGT  errCorrupt
+
+	// length = 1 + int(src[s-5])>>2
+	MOVD $1, R1
+	ADD  R_LEN>>2, R1, R_LEN
+
+	// offset = int(uint32(src[s-4]) | uint32(src[s-3])<<8 | uint32(src[s-2])<<16 | uint32(src[s-1])<<24)
+	MOVWU -4(R_SRC), R_OFF
+	B     doCopy
+
+tagCopy2:
+	// case tagCopy2:
+	// s += 3
+	ADD $3, R_SRC, R_SRC
+
+	// if uint(s) > uint(len(src)) { etc }
+	TEST_SRC()
+
+	// length = 1 + int(src[s-3])>>2
+	MOVD $1, R1
+	ADD  R_LEN>>2, R1, R_LEN
+
+	// offset = int(uint32(src[s-2]) | uint32(src[s-1])<<8)
+	MOVHU -2(R_SRC), R_OFF
+	B     doCopy
+
+tagCopy:
+	// We have a copy tag. We assume that:
+	//	- R_TMP1 == src[s] & 0x03
+	//	- R_LEN == src[s]
+	CMP $2, R_TMP1
+	BEQ tagCopy2
+	BGT tagCopy4
+
+	// case tagCopy1:
+	// s += 2
+	ADD $2, R_SRC, R_SRC
+
+	// if uint(s) > uint(len(src)) { etc }
+	TEST_SRC()
+
+	// offset = int(uint32(src[s-2])&0xe0<<3 | uint32(src[s-1]))
+	// Calculate offset in R_TMP0 in case it is a repeat.
+	MOVD  R_LEN, R_TMP0
+	AND   $0xe0, R_TMP0
+	MOVBU -1(R_SRC), R_TMP1
+	ORR   R_TMP0<<3, R_TMP1, R_TMP0
+
+	// length = 4 + int(src[s-2])>>2&0x7
+	MOVD $7, R1
+	AND  R_LEN>>2, R1, R_LEN
+	ADD  $4, R_LEN, R_LEN
+
+	// check if repeat code with offset 0.
+	CMP $0, R_TMP0
+	BEQ repeatCode
+
+	// This is a regular copy, transfer our temporary value to R_OFF (offset)
+	MOVD R_TMP0, R_OFF
+	B    doCopy
+
+	// This is a repeat code.
+repeatCode:
+	// If length < 9, reuse last offset, with the length already calculated.
+	CMP $9, R_LEN
+	BLT doCopyRepeat
+	BEQ repeatLen1
+	CMP $10, R_LEN
+	BEQ repeatLen2
+
+repeatLen3:
+	// s +=3
+	ADD $3, R_SRC, R_SRC
+
+	// if uint(s) > uint(len(src)) { etc }
+	TEST_SRC()
+
+	// length = uint32(src[s-3]) | (uint32(src[s-2])<<8) | (uint32(src[s-1])<<16) + 65540
+	MOVBU -1(R_SRC), R_TMP0
+	MOVHU -3(R_SRC), R_LEN
+	ORR   R_TMP0<<16, R_LEN, R_LEN
+	ADD   $65540, R_LEN, R_LEN
+	B     doCopyRepeat
+
+repeatLen2:
+	// s +=2
+	ADD $2, R_SRC, R_SRC
+
+	// if uint(s) > uint(len(src)) { etc }
+	TEST_SRC()
+
+	// length = uint32(src[s-2]) | (uint32(src[s-1])<<8) + 260
+	MOVHU -2(R_SRC), R_LEN
+	ADD   $260, R_LEN, R_LEN
+	B     doCopyRepeat
+
+repeatLen1:
+	// s +=1
+	ADD $1, R_SRC, R_SRC
+
+	// if uint(s) > uint(len(src)) { etc }
+	TEST_SRC()
+
+	// length = src[s-1] + 8
+	MOVBU -1(R_SRC), R_LEN
+	ADD   $8, R_LEN, R_LEN
+	B     doCopyRepeat
+
+doCopy:
+	// This is the end of the outer "switch", when we have a copy tag.
+	//
+	// We assume that:
+	//	- R_LEN == length && R_LEN > 0
+	//	- R_OFF == offset
+
+	// if d < offset { etc }
+	MOVD R_DST, R_TMP1
+	SUB  R_DBASE, R_TMP1, R_TMP1
+	CMP  R_OFF, R_TMP1
+	BLT  errCorrupt
+
+	// Repeat values can skip the test above, since any offset > 0 will be in dst.
+doCopyRepeat:
+
+	// if offset <= 0 { etc }
+	CMP $0, R_OFF
+	BLE errCorrupt
+
+	// if length > len(dst)-d { etc }
+	MOVD R_DEND, R_TMP1
+	SUB  R_DST, R_TMP1, R_TMP1
+	CMP  R_TMP1, R_LEN
+	BGT  errCorrupt
+
+	// forwardCopy(dst[d:d+length], dst[d-offset:]); d += length
+	//
+	// Set:
+	//	- R_TMP2 = len(dst)-d
+	//	- R_TMP3 = &dst[d-offset]
+	MOVD R_DEND, R_TMP2
+	SUB  R_DST, R_TMP2, R_TMP2
+	MOVD R_DST, R_TMP3
+	SUB  R_OFF, R_TMP3, R_TMP3
+
+	// !!! 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, R_LEN
+	BGT  slowForwardCopy
+	CMP  $8, R_OFF
+	BLT  slowForwardCopy
+	CMP  $16, R_TMP2
+	BLT  slowForwardCopy
+	MOVD 0(R_TMP3), R_TMP0
+	MOVD R_TMP0, 0(R_DST)
+	MOVD 8(R_TMP3), R_TMP1
+	MOVD R_TMP1, 8(R_DST)
+	ADD  R_LEN, R_DST, R_DST
+	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, R_TMP2, R_TMP2
+	CMP R_TMP2, R_LEN
+	BGT verySlowForwardCopy
+
+	// We want to keep the offset, so we use R_TMP2 from here.
+	MOVD R_OFF, R_TMP2
+
+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
+	//   // R_TMP3, is unchanged.
+	// }
+	CMP  $8, R_TMP2
+	BGE  fixUpSlowForwardCopy
+	MOVD (R_TMP3), R_TMP1
+	MOVD R_TMP1, (R_DST)
+	SUB  R_TMP2, R_LEN, R_LEN
+	ADD  R_TMP2, R_DST, R_DST
+	ADD  R_TMP2, R_TMP2, R_TMP2
+	B    makeOffsetAtLeast8
+
+fixUpSlowForwardCopy:
+	// !!! Add length (which might be negative now) to d (implied by R_DST 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 R_DST to R_TMP0 so that, if
+	// length is positive, copying the remaining length bytes will write to the
+	// right place.
+	MOVD R_DST, R_TMP0
+	ADD  R_LEN, R_DST, R_DST
+
+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, R_LEN
+	BLE  loop
+	MOVD (R_TMP3), R_TMP1
+	MOVD R_TMP1, (R_TMP0)
+	ADD  $8, R_TMP3, R_TMP3
+	ADD  $8, R_TMP0, R_TMP0
+	SUB  $8, R_LEN, R_LEN
+	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 (R_TMP3), R_TMP1
+	MOVB R_TMP1, (R_DST)
+	ADD  $1, R_TMP3, R_TMP3
+	ADD  $1, R_DST, R_DST
+	SUB  $1, R_LEN, R_LEN
+	CBNZ R_LEN, 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 R_DEND, R_DST
+	BNE errCorrupt
+
+	// return 0
+	MOVD $0, ret+48(FP)
+	RET
+
+errCorrupt:
+	// return decodeErrCodeCorrupt
+	MOVD $1, R_TMP0
+	MOVD R_TMP0, ret+48(FP)
+	RET
-- 
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