diff options
Diffstat (limited to 'vendor/github.com/golang/snappy/encode_arm64.s')
| -rw-r--r-- | vendor/github.com/golang/snappy/encode_arm64.s | 722 |
1 files changed, 722 insertions, 0 deletions
diff --git a/vendor/github.com/golang/snappy/encode_arm64.s b/vendor/github.com/golang/snappy/encode_arm64.s new file mode 100644 index 000000000..bf83667d7 --- /dev/null +++ b/vendor/github.com/golang/snappy/encode_arm64.s @@ -0,0 +1,722 @@ +// 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 encode_other.go, except +// where marked with a "!!!". + +// ---------------------------------------------------------------------------- + +// func emitLiteral(dst, lit []byte) int +// +// All local variables fit into registers. The register allocation: +// - R3 len(lit) +// - R4 n +// - R6 return value +// - R8 &dst[i] +// - R10 &lit[0] +// +// The 32 bytes of stack space is to call runtime·memmove. +// +// The unusual register allocation of local variables, such as R10 for the +// source pointer, matches the allocation used at the call site in encodeBlock, +// which makes it easier to manually inline this function. +TEXT ·emitLiteral(SB), NOSPLIT, $32-56 + MOVD dst_base+0(FP), R8 + MOVD lit_base+24(FP), R10 + MOVD lit_len+32(FP), R3 + MOVD R3, R6 + MOVW R3, R4 + SUBW $1, R4, R4 + + CMPW $60, R4 + BLT oneByte + CMPW $256, R4 + BLT twoBytes + +threeBytes: + MOVD $0xf4, R2 + MOVB R2, 0(R8) + MOVW R4, 1(R8) + ADD $3, R8, R8 + ADD $3, R6, R6 + B memmove + +twoBytes: + MOVD $0xf0, R2 + MOVB R2, 0(R8) + MOVB R4, 1(R8) + ADD $2, R8, R8 + ADD $2, R6, R6 + B memmove + +oneByte: + LSLW $2, R4, R4 + MOVB R4, 0(R8) + ADD $1, R8, R8 + ADD $1, R6, R6 + +memmove: + MOVD R6, ret+48(FP) + + // copy(dst[i:], lit) + // + // This means calling runtime·memmove(&dst[i], &lit[0], len(lit)), so we push + // R8, R10 and R3 as arguments. + MOVD R8, 8(RSP) + MOVD R10, 16(RSP) + MOVD R3, 24(RSP) + CALL runtime·memmove(SB) + RET + +// ---------------------------------------------------------------------------- + +// func emitCopy(dst []byte, offset, length int) int +// +// All local variables fit into registers. The register allocation: +// - R3 length +// - R7 &dst[0] +// - R8 &dst[i] +// - R11 offset +// +// The unusual register allocation of local variables, such as R11 for the +// offset, matches the allocation used at the call site in encodeBlock, which +// makes it easier to manually inline this function. +TEXT ·emitCopy(SB), NOSPLIT, $0-48 + MOVD dst_base+0(FP), R8 + MOVD R8, R7 + MOVD offset+24(FP), R11 + MOVD length+32(FP), R3 + +loop0: + // for length >= 68 { etc } + CMPW $68, R3 + BLT step1 + + // Emit a length 64 copy, encoded as 3 bytes. + MOVD $0xfe, R2 + MOVB R2, 0(R8) + MOVW R11, 1(R8) + ADD $3, R8, R8 + SUB $64, R3, R3 + B loop0 + +step1: + // if length > 64 { etc } + CMP $64, R3 + BLE step2 + + // Emit a length 60 copy, encoded as 3 bytes. + MOVD $0xee, R2 + MOVB R2, 0(R8) + MOVW R11, 1(R8) + ADD $3, R8, R8 + SUB $60, R3, R3 + +step2: + // if length >= 12 || offset >= 2048 { goto step3 } + CMP $12, R3 + BGE step3 + CMPW $2048, R11 + BGE step3 + + // Emit the remaining copy, encoded as 2 bytes. + MOVB R11, 1(R8) + LSRW $3, R11, R11 + AND $0xe0, R11, R11 + SUB $4, R3, R3 + LSLW $2, R3 + AND $0xff, R3, R3 + ORRW R3, R11, R11 + ORRW $1, R11, R11 + MOVB R11, 0(R8) + ADD $2, R8, R8 + + // Return the number of bytes written. + SUB R7, R8, R8 + MOVD R8, ret+40(FP) + RET + +step3: + // Emit the remaining copy, encoded as 3 bytes. + SUB $1, R3, R3 + AND $0xff, R3, R3 + LSLW $2, R3, R3 + ORRW $2, R3, R3 + MOVB R3, 0(R8) + MOVW R11, 1(R8) + ADD $3, R8, R8 + + // Return the number of bytes written. + SUB R7, R8, R8 + MOVD R8, ret+40(FP) + RET + +// ---------------------------------------------------------------------------- + +// func extendMatch(src []byte, i, j int) int +// +// All local variables fit into registers. The register allocation: +// - R6 &src[0] +// - R7 &src[j] +// - R13 &src[len(src) - 8] +// - R14 &src[len(src)] +// - R15 &src[i] +// +// The unusual register allocation of local variables, such as R15 for a source +// pointer, matches the allocation used at the call site in encodeBlock, which +// makes it easier to manually inline this function. +TEXT ·extendMatch(SB), NOSPLIT, $0-48 + MOVD src_base+0(FP), R6 + MOVD src_len+8(FP), R14 + MOVD i+24(FP), R15 + MOVD j+32(FP), R7 + ADD R6, R14, R14 + ADD R6, R15, R15 + ADD R6, R7, R7 + MOVD R14, R13 + SUB $8, R13, R13 + +cmp8: + // As long as we are 8 or more bytes before the end of src, we can load and + // compare 8 bytes at a time. If those 8 bytes are equal, repeat. + CMP R13, R7 + BHI cmp1 + MOVD (R15), R3 + MOVD (R7), R4 + CMP R4, R3 + BNE bsf + ADD $8, R15, R15 + ADD $8, R7, R7 + B cmp8 + +bsf: + // If those 8 bytes were not equal, XOR the two 8 byte values, and return + // the index of the first byte that differs. + // RBIT reverses the bit order, then CLZ counts the leading zeros, the + // combination of which finds the least significant bit which is set. + // The arm64 architecture is little-endian, and the shift by 3 converts + // a bit index to a byte index. + EOR R3, R4, R4 + RBIT R4, R4 + CLZ R4, R4 + ADD R4>>3, R7, R7 + + // Convert from &src[ret] to ret. + SUB R6, R7, R7 + MOVD R7, ret+40(FP) + RET + +cmp1: + // In src's tail, compare 1 byte at a time. + CMP R7, R14 + BLS extendMatchEnd + MOVB (R15), R3 + MOVB (R7), R4 + CMP R4, R3 + BNE extendMatchEnd + ADD $1, R15, R15 + ADD $1, R7, R7 + B cmp1 + +extendMatchEnd: + // Convert from &src[ret] to ret. + SUB R6, R7, R7 + MOVD R7, ret+40(FP) + RET + +// ---------------------------------------------------------------------------- + +// func encodeBlock(dst, src []byte) (d int) +// +// All local variables fit into registers, other than "var table". The register +// allocation: +// - R3 . . +// - R4 . . +// - R5 64 shift +// - R6 72 &src[0], tableSize +// - R7 80 &src[s] +// - R8 88 &dst[d] +// - R9 96 sLimit +// - R10 . &src[nextEmit] +// - R11 104 prevHash, currHash, nextHash, offset +// - R12 112 &src[base], skip +// - R13 . &src[nextS], &src[len(src) - 8] +// - R14 . len(src), bytesBetweenHashLookups, &src[len(src)], x +// - R15 120 candidate +// - R16 . hash constant, 0x1e35a7bd +// - R17 . &table +// - . 128 table +// +// The second column (64, 72, etc) is the stack offset to spill the registers +// when calling other functions. We could pack this slightly tighter, but it's +// simpler to have a dedicated spill map independent of the function called. +// +// "var table [maxTableSize]uint16" takes up 32768 bytes of stack space. An +// extra 64 bytes, to call other functions, and an extra 64 bytes, to spill +// local variables (registers) during calls gives 32768 + 64 + 64 = 32896. +TEXT ·encodeBlock(SB), 0, $32896-56 + MOVD dst_base+0(FP), R8 + MOVD src_base+24(FP), R7 + MOVD src_len+32(FP), R14 + + // shift, tableSize := uint32(32-8), 1<<8 + MOVD $24, R5 + MOVD $256, R6 + MOVW $0xa7bd, R16 + MOVKW $(0x1e35<<16), R16 + +calcShift: + // for ; tableSize < maxTableSize && tableSize < len(src); tableSize *= 2 { + // shift-- + // } + MOVD $16384, R2 + CMP R2, R6 + BGE varTable + CMP R14, R6 + BGE varTable + SUB $1, R5, R5 + LSL $1, R6, R6 + B calcShift + +varTable: + // var table [maxTableSize]uint16 + // + // In the asm code, unlike the Go code, we can zero-initialize only the + // first tableSize elements. Each uint16 element is 2 bytes and each + // iterations writes 64 bytes, so we can do only tableSize/32 writes + // instead of the 2048 writes that would zero-initialize all of table's + // 32768 bytes. This clear could overrun the first tableSize elements, but + // it won't overrun the allocated stack size. + ADD $128, RSP, R17 + MOVD R17, R4 + + // !!! R6 = &src[tableSize] + ADD R6<<1, R17, R6 + +memclr: + STP.P (ZR, ZR), 64(R4) + STP (ZR, ZR), -48(R4) + STP (ZR, ZR), -32(R4) + STP (ZR, ZR), -16(R4) + CMP R4, R6 + BHI memclr + + // !!! R6 = &src[0] + MOVD R7, R6 + + // sLimit := len(src) - inputMargin + MOVD R14, R9 + SUB $15, R9, R9 + + // !!! Pre-emptively spill R5, R6 and R9 to the stack. Their values don't + // change for the rest of the function. + MOVD R5, 64(RSP) + MOVD R6, 72(RSP) + MOVD R9, 96(RSP) + + // nextEmit := 0 + MOVD R6, R10 + + // s := 1 + ADD $1, R7, R7 + + // nextHash := hash(load32(src, s), shift) + MOVW 0(R7), R11 + MULW R16, R11, R11 + LSRW R5, R11, R11 + +outer: + // for { etc } + + // skip := 32 + MOVD $32, R12 + + // nextS := s + MOVD R7, R13 + + // candidate := 0 + MOVD $0, R15 + +inner0: + // for { etc } + + // s := nextS + MOVD R13, R7 + + // bytesBetweenHashLookups := skip >> 5 + MOVD R12, R14 + LSR $5, R14, R14 + + // nextS = s + bytesBetweenHashLookups + ADD R14, R13, R13 + + // skip += bytesBetweenHashLookups + ADD R14, R12, R12 + + // if nextS > sLimit { goto emitRemainder } + MOVD R13, R3 + SUB R6, R3, R3 + CMP R9, R3 + BHI emitRemainder + + // candidate = int(table[nextHash]) + MOVHU 0(R17)(R11<<1), R15 + + // table[nextHash] = uint16(s) + MOVD R7, R3 + SUB R6, R3, R3 + + MOVH R3, 0(R17)(R11<<1) + + // nextHash = hash(load32(src, nextS), shift) + MOVW 0(R13), R11 + MULW R16, R11 + LSRW R5, R11, R11 + + // if load32(src, s) != load32(src, candidate) { continue } break + MOVW 0(R7), R3 + MOVW (R6)(R15*1), R4 + CMPW R4, R3 + BNE inner0 + +fourByteMatch: + // As per the encode_other.go code: + // + // A 4-byte match has been found. We'll later see etc. + + // !!! Jump to a fast path for short (<= 16 byte) literals. See the comment + // on inputMargin in encode.go. + MOVD R7, R3 + SUB R10, R3, R3 + CMP $16, R3 + BLE emitLiteralFastPath + + // ---------------------------------------- + // Begin inline of the emitLiteral call. + // + // d += emitLiteral(dst[d:], src[nextEmit:s]) + + MOVW R3, R4 + SUBW $1, R4, R4 + + MOVW $60, R2 + CMPW R2, R4 + BLT inlineEmitLiteralOneByte + MOVW $256, R2 + CMPW R2, R4 + BLT inlineEmitLiteralTwoBytes + +inlineEmitLiteralThreeBytes: + MOVD $0xf4, R1 + MOVB R1, 0(R8) + MOVW R4, 1(R8) + ADD $3, R8, R8 + B inlineEmitLiteralMemmove + +inlineEmitLiteralTwoBytes: + MOVD $0xf0, R1 + MOVB R1, 0(R8) + MOVB R4, 1(R8) + ADD $2, R8, R8 + B inlineEmitLiteralMemmove + +inlineEmitLiteralOneByte: + LSLW $2, R4, R4 + MOVB R4, 0(R8) + ADD $1, R8, R8 + +inlineEmitLiteralMemmove: + // Spill local variables (registers) onto the stack; call; unspill. + // + // copy(dst[i:], lit) + // + // This means calling runtime·memmove(&dst[i], &lit[0], len(lit)), so we push + // R8, R10 and R3 as arguments. + MOVD R8, 8(RSP) + MOVD R10, 16(RSP) + MOVD R3, 24(RSP) + + // Finish the "d +=" part of "d += emitLiteral(etc)". + ADD R3, R8, R8 + MOVD R7, 80(RSP) + MOVD R8, 88(RSP) + MOVD R15, 120(RSP) + CALL runtime·memmove(SB) + MOVD 64(RSP), R5 + MOVD 72(RSP), R6 + MOVD 80(RSP), R7 + MOVD 88(RSP), R8 + MOVD 96(RSP), R9 + MOVD 120(RSP), R15 + ADD $128, RSP, R17 + MOVW $0xa7bd, R16 + MOVKW $(0x1e35<<16), R16 + B inner1 + +inlineEmitLiteralEnd: + // End inline of the emitLiteral call. + // ---------------------------------------- + +emitLiteralFastPath: + // !!! Emit the 1-byte encoding "uint8(len(lit)-1)<<2". + MOVB R3, R4 + SUBW $1, R4, R4 + AND $0xff, R4, R4 + LSLW $2, R4, R4 + MOVB R4, (R8) + ADD $1, R8, R8 + + // !!! Implement the copy from lit to dst as a 16-byte load and store. + // (Encode's documentation says that dst and src must not overlap.) + // + // This always copies 16 bytes, instead of only len(lit) bytes, but that's + // OK. Subsequent iterations will fix up the overrun. + // + // 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(R10), (R0, R1) + STP (R0, R1), 0(R8) + ADD R3, R8, R8 + +inner1: + // for { etc } + + // base := s + MOVD R7, R12 + + // !!! offset := base - candidate + MOVD R12, R11 + SUB R15, R11, R11 + SUB R6, R11, R11 + + // ---------------------------------------- + // Begin inline of the extendMatch call. + // + // s = extendMatch(src, candidate+4, s+4) + + // !!! R14 = &src[len(src)] + MOVD src_len+32(FP), R14 + ADD R6, R14, R14 + + // !!! R13 = &src[len(src) - 8] + MOVD R14, R13 + SUB $8, R13, R13 + + // !!! R15 = &src[candidate + 4] + ADD $4, R15, R15 + ADD R6, R15, R15 + + // !!! s += 4 + ADD $4, R7, R7 + +inlineExtendMatchCmp8: + // As long as we are 8 or more bytes before the end of src, we can load and + // compare 8 bytes at a time. If those 8 bytes are equal, repeat. + CMP R13, R7 + BHI inlineExtendMatchCmp1 + MOVD (R15), R3 + MOVD (R7), R4 + CMP R4, R3 + BNE inlineExtendMatchBSF + ADD $8, R15, R15 + ADD $8, R7, R7 + B inlineExtendMatchCmp8 + +inlineExtendMatchBSF: + // If those 8 bytes were not equal, XOR the two 8 byte values, and return + // the index of the first byte that differs. + // RBIT reverses the bit order, then CLZ counts the leading zeros, the + // combination of which finds the least significant bit which is set. + // The arm64 architecture is little-endian, and the shift by 3 converts + // a bit index to a byte index. + EOR R3, R4, R4 + RBIT R4, R4 + CLZ R4, R4 + ADD R4>>3, R7, R7 + B inlineExtendMatchEnd + +inlineExtendMatchCmp1: + // In src's tail, compare 1 byte at a time. + CMP R7, R14 + BLS inlineExtendMatchEnd + MOVB (R15), R3 + MOVB (R7), R4 + CMP R4, R3 + BNE inlineExtendMatchEnd + ADD $1, R15, R15 + ADD $1, R7, R7 + B inlineExtendMatchCmp1 + +inlineExtendMatchEnd: + // End inline of the extendMatch call. + // ---------------------------------------- + + // ---------------------------------------- + // Begin inline of the emitCopy call. + // + // d += emitCopy(dst[d:], base-candidate, s-base) + + // !!! length := s - base + MOVD R7, R3 + SUB R12, R3, R3 + +inlineEmitCopyLoop0: + // for length >= 68 { etc } + MOVW $68, R2 + CMPW R2, R3 + BLT inlineEmitCopyStep1 + + // Emit a length 64 copy, encoded as 3 bytes. + MOVD $0xfe, R1 + MOVB R1, 0(R8) + MOVW R11, 1(R8) + ADD $3, R8, R8 + SUBW $64, R3, R3 + B inlineEmitCopyLoop0 + +inlineEmitCopyStep1: + // if length > 64 { etc } + MOVW $64, R2 + CMPW R2, R3 + BLE inlineEmitCopyStep2 + + // Emit a length 60 copy, encoded as 3 bytes. + MOVD $0xee, R1 + MOVB R1, 0(R8) + MOVW R11, 1(R8) + ADD $3, R8, R8 + SUBW $60, R3, R3 + +inlineEmitCopyStep2: + // if length >= 12 || offset >= 2048 { goto inlineEmitCopyStep3 } + MOVW $12, R2 + CMPW R2, R3 + BGE inlineEmitCopyStep3 + MOVW $2048, R2 + CMPW R2, R11 + BGE inlineEmitCopyStep3 + + // Emit the remaining copy, encoded as 2 bytes. + MOVB R11, 1(R8) + LSRW $8, R11, R11 + LSLW $5, R11, R11 + SUBW $4, R3, R3 + AND $0xff, R3, R3 + LSLW $2, R3, R3 + ORRW R3, R11, R11 + ORRW $1, R11, R11 + MOVB R11, 0(R8) + ADD $2, R8, R8 + B inlineEmitCopyEnd + +inlineEmitCopyStep3: + // Emit the remaining copy, encoded as 3 bytes. + SUBW $1, R3, R3 + LSLW $2, R3, R3 + ORRW $2, R3, R3 + MOVB R3, 0(R8) + MOVW R11, 1(R8) + ADD $3, R8, R8 + +inlineEmitCopyEnd: + // End inline of the emitCopy call. + // ---------------------------------------- + + // nextEmit = s + MOVD R7, R10 + + // if s >= sLimit { goto emitRemainder } + MOVD R7, R3 + SUB R6, R3, R3 + CMP R3, R9 + BLS emitRemainder + + // As per the encode_other.go code: + // + // We could immediately etc. + + // x := load64(src, s-1) + MOVD -1(R7), R14 + + // prevHash := hash(uint32(x>>0), shift) + MOVW R14, R11 + MULW R16, R11, R11 + LSRW R5, R11, R11 + + // table[prevHash] = uint16(s-1) + MOVD R7, R3 + SUB R6, R3, R3 + SUB $1, R3, R3 + + MOVHU R3, 0(R17)(R11<<1) + + // currHash := hash(uint32(x>>8), shift) + LSR $8, R14, R14 + MOVW R14, R11 + MULW R16, R11, R11 + LSRW R5, R11, R11 + + // candidate = int(table[currHash]) + MOVHU 0(R17)(R11<<1), R15 + + // table[currHash] = uint16(s) + ADD $1, R3, R3 + MOVHU R3, 0(R17)(R11<<1) + + // if uint32(x>>8) == load32(src, candidate) { continue } + MOVW (R6)(R15*1), R4 + CMPW R4, R14 + BEQ inner1 + + // nextHash = hash(uint32(x>>16), shift) + LSR $8, R14, R14 + MOVW R14, R11 + MULW R16, R11, R11 + LSRW R5, R11, R11 + + // s++ + ADD $1, R7, R7 + + // break out of the inner1 for loop, i.e. continue the outer loop. + B outer + +emitRemainder: + // if nextEmit < len(src) { etc } + MOVD src_len+32(FP), R3 + ADD R6, R3, R3 + CMP R3, R10 + BEQ encodeBlockEnd + + // d += emitLiteral(dst[d:], src[nextEmit:]) + // + // Push args. + MOVD R8, 8(RSP) + MOVD $0, 16(RSP) // Unnecessary, as the callee ignores it, but conservative. + MOVD $0, 24(RSP) // Unnecessary, as the callee ignores it, but conservative. + MOVD R10, 32(RSP) + SUB R10, R3, R3 + MOVD R3, 40(RSP) + MOVD R3, 48(RSP) // Unnecessary, as the callee ignores it, but conservative. + + // Spill local variables (registers) onto the stack; call; unspill. + MOVD R8, 88(RSP) + CALL ·emitLiteral(SB) + MOVD 88(RSP), R8 + + // Finish the "d +=" part of "d += emitLiteral(etc)". + MOVD 56(RSP), R1 + ADD R1, R8, R8 + +encodeBlockEnd: + MOVD dst_base+0(FP), R3 + SUB R3, R8, R8 + MOVD R8, d+48(FP) + RET |