From: Shengjing Zhu Date: Sun, 31 Jan 2021 22:33:53 +0800 Subject: Backport go1.16 fix on arm64 Origin: backport, https://github.com/golang/snappy/pull/56 --- decode_arm64.s | 45 +++++++++++++------------------- encode_arm64.s | 81 +++++++++++++++++++++++++++------------------------------- 2 files changed, 55 insertions(+), 71 deletions(-) diff --git a/decode_arm64.s b/decode_arm64.s index bfafa0c..7a3ead1 100644 --- a/decode_arm64.s +++ b/decode_arm64.s @@ -70,7 +70,7 @@ loop: // x := uint32(src[s] >> 2) // switch MOVW $60, R1 - ADD R4>>2, ZR, R4 + LSRW $2, R4, R4 CMPW R4, R1 BLS tagLit60Plus @@ -111,13 +111,12 @@ doLit: // 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). - MOVD $16, R1 - CMP R1, R4 - BGT callMemmove - CMP R1, R2 - BLT callMemmove - CMP R1, R3 - BLT callMemmove + 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.) @@ -130,9 +129,8 @@ doLit: // 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. - - VLD1 0(R6), [V0.B16] - VST1 [V0.B16], 0(R7) + LDP 0(R6), (R14, R15) + STP (R14, R15), 0(R7) // d += length // s += length @@ -210,8 +208,7 @@ tagLit61: B doLit tagLit62Plus: - MOVW $62, R1 - CMPW R1, R4 + CMPW $62, R4 BHI tagLit63 // case x == 62: @@ -273,10 +270,9 @@ tagCopy: // We have a copy tag. We assume that: // - R3 == src[s] & 0x03 // - R4 == src[s] - MOVD $2, R1 - CMP R1, R3 - BEQ tagCopy2 - BGT tagCopy4 + CMP $2, R3 + BEQ tagCopy2 + BGT tagCopy4 // case tagCopy1: // s += 2 @@ -346,13 +342,11 @@ doCopy: // } // copy 16 bytes // d += length - MOVD $16, R1 - MOVD $8, R0 - CMP R1, R4 + CMP $16, R4 BGT slowForwardCopy - CMP R0, R5 + CMP $8, R5 BLT slowForwardCopy - CMP R1, R14 + CMP $16, R14 BLT slowForwardCopy MOVD 0(R15), R2 MOVD R2, 0(R7) @@ -426,8 +420,7 @@ makeOffsetAtLeast8: // // The two previous lines together means that d-offset, and therefore // // R15, is unchanged. // } - MOVD $8, R1 - CMP R1, R5 + CMP $8, R5 BGE fixUpSlowForwardCopy MOVD (R15), R3 MOVD R3, (R7) @@ -477,9 +470,7 @@ verySlowForwardCopy: ADD $1, R15, R15 ADD $1, R7, R7 SUB $1, R4, R4 - MOVD $0, R1 - CMP R1, R4 - BNE verySlowForwardCopy + CBNZ R4, verySlowForwardCopy B loop // The code above handles copy tags. diff --git a/encode_arm64.s b/encode_arm64.s index 1f565ee..bf83667 100644 --- a/encode_arm64.s +++ b/encode_arm64.s @@ -35,11 +35,9 @@ TEXT ·emitLiteral(SB), NOSPLIT, $32-56 MOVW R3, R4 SUBW $1, R4, R4 - MOVW $60, R2 - CMPW R2, R4 + CMPW $60, R4 BLT oneByte - MOVW $256, R2 - CMPW R2, R4 + CMPW $256, R4 BLT twoBytes threeBytes: @@ -98,8 +96,7 @@ TEXT ·emitCopy(SB), NOSPLIT, $0-48 loop0: // for length >= 68 { etc } - MOVW $68, R2 - CMPW R2, R3 + CMPW $68, R3 BLT step1 // Emit a length 64 copy, encoded as 3 bytes. @@ -112,9 +109,8 @@ loop0: step1: // if length > 64 { etc } - MOVD $64, R2 - CMP R2, R3 - BLE step2 + CMP $64, R3 + BLE step2 // Emit a length 60 copy, encoded as 3 bytes. MOVD $0xee, R2 @@ -125,11 +121,9 @@ step1: step2: // if length >= 12 || offset >= 2048 { goto step3 } - MOVD $12, R2 - CMP R2, R3 + CMP $12, R3 BGE step3 - MOVW $2048, R2 - CMPW R2, R11 + CMPW $2048, R11 BGE step3 // Emit the remaining copy, encoded as 2 bytes. @@ -295,27 +289,24 @@ 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 VST1 - // 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. + // 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 - // zero the SIMD registers - VEOR V0.B16, V0.B16, V0.B16 - VEOR V1.B16, V1.B16, V1.B16 - VEOR V2.B16, V2.B16, V2.B16 - VEOR V3.B16, V3.B16, V3.B16 - memclr: - VST1.P [V0.B16, V1.B16, V2.B16, V3.B16], 64(R4) - CMP R4, R6 - BHI 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 @@ -404,8 +395,7 @@ fourByteMatch: // on inputMargin in encode.go. MOVD R7, R3 SUB R10, R3, R3 - MOVD $16, R2 - CMP R2, R3 + CMP $16, R3 BLE emitLiteralFastPath // ---------------------------------------- @@ -454,18 +444,21 @@ inlineEmitLiteralMemmove: 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 - B inner1 + 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. @@ -489,9 +482,9 @@ emitLiteralFastPath: // 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. - VLD1 0(R10), [V0.B16] - VST1 [V0.B16], 0(R8) - ADD R3, R8, R8 + LDP 0(R10), (R0, R1) + STP (R0, R1), 0(R8) + ADD R3, R8, R8 inner1: // for { etc }