From ee8972cd126f0d575be90c0ffbb08fc09d6ede19 Mon Sep 17 00:00:00 2001 From: "Ruixin(Peter) Bao" Date: Tue, 3 Dec 2019 16:06:18 -0500 Subject: [PATCH] math/big: rewrite addVW to use fast path on s390x MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Rewrite addVW to use a fast path and remove the original vector and non vector implementation of addVW in assembly. This CL uses a similar idea as CL 164968, where we copy the rest of words when we know carry bit is zero. In addition, since we are copying vector of words, a faster implementation of copy is written in this CL to copy a word or multiple words at a time. Benchmarks: name old time/op new time/op delta AddVW/1-18 4.56ns ± 0% 4.01ns ± 6% -12.14% (p=0.000 n=18+20) AddVW/2-18 5.54ns ± 0% 4.42ns ± 5% -20.20% (p=0.000 n=18+20) AddVW/3-18 6.55ns ± 0% 4.61ns ± 0% -29.62% (p=0.000 n=16+18) AddVW/4-18 6.11ns ± 2% 5.12ns ± 6% -16.19% (p=0.000 n=20+20) AddVW/5-18 7.32ns ± 4% 5.14ns ± 0% -29.77% (p=0.000 n=20+19) AddVW/10-18 10.6ns ± 2% 7.2ns ± 1% -31.47% (p=0.000 n=20+20) AddVW/100-18 49.6ns ± 2% 18.0ns ± 0% -63.63% (p=0.000 n=20+20) AddVW/1000-18 465ns ± 3% 244ns ± 0% -47.54% (p=0.000 n=20+20) AddVW/10000-18 4.99µs ± 4% 2.97µs ± 0% -40.54% (p=0.000 n=20+20) AddVW/100000-18 48.3µs ± 3% 30.8µs ± 1% -36.29% (p=0.000 n=20+20) [Geo mean] 58.1ns 38.0ns -34.57% name old speed new speed delta AddVW/1-18 1.76GB/s ± 0% 2.00GB/s ± 6% +14.04% (p=0.000 n=20+20) AddVW/2-18 2.89GB/s ± 0% 3.63GB/s ± 5% +25.55% (p=0.000 n=18+20) AddVW/3-18 3.66GB/s ± 0% 5.21GB/s ± 0% +42.25% (p=0.000 n=18+19) AddVW/4-18 5.24GB/s ± 2% 6.27GB/s ± 6% +19.61% (p=0.000 n=20+20) AddVW/5-18 5.47GB/s ± 4% 7.78GB/s ± 0% +42.28% (p=0.000 n=20+18) AddVW/10-18 7.55GB/s ± 2% 11.04GB/s ± 1% +46.09% (p=0.000 n=20+20) AddVW/100-18 16.1GB/s ± 2% 44.3GB/s ± 0% +174.77% (p=0.000 n=20+20) AddVW/1000-18 17.2GB/s ± 3% 32.8GB/s ± 1% +90.58% (p=0.000 n=20+20) AddVW/10000-18 16.0GB/s ± 4% 26.9GB/s ± 0% +68.11% (p=0.000 n=20+20) AddVW/100000-18 16.6GB/s ± 3% 26.0GB/s ± 1% +56.94% (p=0.000 n=20+20) [Geo mean] 7.03GB/s 10.75GB/s +52.93% Change-Id: Idbb73f3178311bd2b18a93bdc1e48f26869d2f6a Reviewed-on: https://go-review.googlesource.com/c/go/+/209679 Reviewed-by: Michael Munday Run-TryBot: Michael Munday TryBot-Result: Gobot Gobot --- src/math/big/arith_decl_s390x.go | 3 - src/math/big/arith_s390x.s | 289 +++++++++---------------------- src/math/big/arith_s390x_test.go | 5 +- 3 files changed, 84 insertions(+), 213 deletions(-) diff --git a/src/math/big/arith_decl_s390x.go b/src/math/big/arith_decl_s390x.go index 0f11481f6d2ed..38fefcc7b0e55 100644 --- a/src/math/big/arith_decl_s390x.go +++ b/src/math/big/arith_decl_s390x.go @@ -12,9 +12,6 @@ func addVV_novec(z, x, y []Word) (c Word) func subVV_check(z, x, y []Word) (c Word) func subVV_vec(z, x, y []Word) (c Word) func subVV_novec(z, x, y []Word) (c Word) -func addVW_check(z, x []Word, y Word) (c Word) -func addVW_vec(z, x []Word, y Word) (c Word) -func addVW_novec(z, x []Word, y Word) (c Word) func subVW_check(z, x []Word, y Word) (c Word) func subVW_vec(z, x []Word, y Word) (c Word) func subVW_novec(z, x []Word, y Word) (c Word) diff --git a/src/math/big/arith_s390x.s b/src/math/big/arith_s390x.s index 319a7754eded7..f0464df201ecf 100644 --- a/src/math/big/arith_s390x.s +++ b/src/math/big/arith_s390x.s @@ -541,216 +541,93 @@ E1: RET TEXT ·addVW(SB), NOSPLIT, $0 - MOVD addwvectorfacility+0x00(SB), R1 - BR (R1) - -TEXT ·addVW_check(SB), NOSPLIT, $0 - MOVB ·hasVX(SB), R1 - CMPBEQ R1, $1, vectorimpl // vectorfacility = 1, vector supported - MOVD $addwvectorfacility+0x00(SB), R1 - MOVD $·addVW_novec(SB), R2 - MOVD R2, 0(R1) - - // MOVD $·addVW_novec(SB), 0(R1) - BR ·addVW_novec(SB) - -vectorimpl: - MOVD $addwvectorfacility+0x00(SB), R1 - MOVD $·addVW_vec(SB), R2 - MOVD R2, 0(R1) - - // MOVD $·addVW_vec(SB), 0(R1) - BR ·addVW_vec(SB) - -GLOBL addwvectorfacility+0x00(SB), NOPTR, $8 -DATA addwvectorfacility+0x00(SB)/8, $·addVW_check(SB) - -// func addVW_vec(z, x []Word, y Word) (c Word) -TEXT ·addVW_vec(SB), NOSPLIT, $0 - MOVD z_len+8(FP), R3 - MOVD x+24(FP), R8 - MOVD y+48(FP), R4 // c = y - MOVD z+0(FP), R2 - - MOVD $0, R0 // make sure it's zero - MOVD $0, R10 // i = 0 - MOVD R8, R5 - MOVD R2, R7 - - // s/JL/JMP/ below to disable the unrolled loop - SUB $4, R3 // n -= 4 - BLT v10 // if n < 0 goto v10 - SUB $12, R3 - BLT A10 - - // n >= 0 - // regular loop body unrolled 16x - - VZERO V0 // prepare V0 to be final carry register - VZERO V9 // to ensure upper half is zero - VLVGG $1, R4, V9 - -UU1: - VLM 0(R5), V1, V4 // 64-bytes into V1..V4 - ADD $64, R5 - VPDI $0x4, V1, V1, V1 // flip the doublewords to big-endian order - VPDI $0x4, V2, V2, V2 // flip the doublewords to big-endian order - - VACCCQ V1, V9, V0, V25 - VACQ V1, V9, V0, V17 - VZERO V9 - VACCCQ V2, V9, V25, V26 - VACQ V2, V9, V25, V18 - - VLM 0(R5), V5, V6 // 32-bytes into V5..V6 - ADD $32, R5 - - VPDI $0x4, V3, V3, V3 // flip the doublewords to big-endian order - VPDI $0x4, V4, V4, V4 // flip the doublewords to big-endian order - - VACCCQ V3, V9, V26, V27 - VACQ V3, V9, V26, V19 - VACCCQ V4, V9, V27, V28 - VACQ V4, V9, V27, V20 - - VLM 0(R5), V7, V8 // 32-bytes into V7..V8 - ADD $32, R5 - - VPDI $0x4, V5, V5, V5 // flip the doublewords to big-endian order - VPDI $0x4, V6, V6, V6 // flip the doublewords to big-endian order - - VACCCQ V5, V9, V28, V29 - VACQ V5, V9, V28, V21 - VACCCQ V6, V9, V29, V30 - VACQ V6, V9, V29, V22 - - VPDI $0x4, V7, V7, V7 // flip the doublewords to big-endian order - VPDI $0x4, V8, V8, V8 // flip the doublewords to big-endian order - - VACCCQ V7, V9, V30, V31 - VACQ V7, V9, V30, V23 - VACCCQ V8, V9, V31, V0 // V0 has carry-over - VACQ V8, V9, V31, V24 - - VPDI $0x4, V17, V17, V17 // flip the doublewords to big-endian order - VPDI $0x4, V18, V18, V18 // flip the doublewords to big-endian order - VPDI $0x4, V19, V19, V19 // flip the doublewords to big-endian order - VPDI $0x4, V20, V20, V20 // flip the doublewords to big-endian order - VPDI $0x4, V21, V21, V21 // flip the doublewords to big-endian order - VPDI $0x4, V22, V22, V22 // flip the doublewords to big-endian order - VPDI $0x4, V23, V23, V23 // flip the doublewords to big-endian order - VPDI $0x4, V24, V24, V24 // flip the doublewords to big-endian order - VSTM V17, V24, 0(R7) // 128-bytes into z - ADD $128, R7 - ADD $128, R10 // i += 16 - SUB $16, R3 // n -= 16 - BGE UU1 // if n >= 0 goto U1 - VLGVG $1, V0, R4 // put cf into R4 in case we branch to v10 - -A10: - ADD $12, R3 // n += 16 - - // s/JL/JMP/ below to disable the unrolled loop - - BLT v10 // if n < 0 goto v10 - -U4: // n >= 0 - // regular loop body unrolled 4x - MOVD 0(R8)(R10*1), R5 - MOVD 8(R8)(R10*1), R6 - MOVD 16(R8)(R10*1), R7 - MOVD 24(R8)(R10*1), R1 - ADDC R4, R5 - ADDE R0, R6 - ADDE R0, R7 - ADDE R0, R1 - ADDE R0, R0 - MOVD R0, R4 // save CF - SUB R0, R0 - MOVD R5, 0(R2)(R10*1) - MOVD R6, 8(R2)(R10*1) - MOVD R7, 16(R2)(R10*1) - MOVD R1, 24(R2)(R10*1) - - ADD $32, R10 // i += 4 -> i +=32 - SUB $4, R3 // n -= 4 - BGE U4 // if n >= 0 goto U4 - -v10: - ADD $4, R3 // n += 4 - BLE E10 // if n <= 0 goto E4 - -L4: // n > 0 - MOVD 0(R8)(R10*1), R5 - ADDC R4, R5 + MOVD z_len+8(FP), R5 // length of z + MOVD x+24(FP), R6 + MOVD y+48(FP), R7 // c = y + MOVD z+0(FP), R8 + + CMPBEQ R5, $0, returnC // if len(z) == 0, we can have an early return + + // Add the first two words, and determine which path (copy path or loop path) to take based on the carry flag. + ADDC 0(R6), R7 + MOVD R7, 0(R8) + CMPBEQ R5, $1, returnResult // len(z) == 1 + MOVD $0, R9 + ADDE 8(R6), R9 + MOVD R9, 8(R8) + CMPBEQ R5, $2, returnResult // len(z) == 2 + + // Update the counters + MOVD $16, R12 // i = 2 + MOVD $-2(R5), R5 // n = n - 2 + +loopOverEachWord: + BRC $12, copySetup // carry = 0, copy the rest + MOVD $1, R9 + + // Originally we used the carry flag generated in the previous iteration + // (i.e: ADDE could be used here to do the addition). However, since we + // already know carry is 1 (otherwise we will go to copy section), we can use + // ADDC here so the current iteration does not depend on the carry flag + // generated in the previous iteration. This could be useful when branch prediction happens. + ADDC 0(R6)(R12*1), R9 + MOVD R9, 0(R8)(R12*1) // z[i] = x[i] + c + + MOVD $8(R12), R12 // i++ + BRCTG R5, loopOverEachWord // n-- + +// Return the current carry value +returnResult: + MOVD $0, R0 ADDE R0, R0 - MOVD R0, R4 // save CF - SUB R0, R0 - MOVD R5, 0(R2)(R10*1) - - ADD $8, R10 // i++ - SUB $1, R3 // n-- - BGT L4 // if n > 0 goto L4 - -E10: - MOVD R4, c+56(FP) // return c - + MOVD R0, c+56(FP) RET -TEXT ·addVW_novec(SB), NOSPLIT, $0 - // DI = R3, CX = R4, SI = r10, r8 = r8, r10 = r2 , r11 = r5, r12 = r6, r13 = r7, r14 = r1 (R0 set to 0) - MOVD z_len+8(FP), R3 - MOVD x+24(FP), R8 - MOVD y+48(FP), R4 // c = y - MOVD z+0(FP), R2 - MOVD $0, R0 // make sure it's 0 - MOVD $0, R10 // i = 0 - - // s/JL/JMP/ below to disable the unrolled loop - SUB $4, R3 // n -= 4 - BLT v4 // if n < 4 goto v4 - -U4: // n >= 0 - // regular loop body unrolled 4x - MOVD 0(R8)(R10*1), R5 - MOVD 8(R8)(R10*1), R6 - MOVD 16(R8)(R10*1), R7 - MOVD 24(R8)(R10*1), R1 - ADDC R4, R5 - ADDE R0, R6 - ADDE R0, R7 - ADDE R0, R1 - ADDE R0, R0 - MOVD R0, R4 // save CF - SUB R0, R0 - MOVD R5, 0(R2)(R10*1) - MOVD R6, 8(R2)(R10*1) - MOVD R7, 16(R2)(R10*1) - MOVD R1, 24(R2)(R10*1) - - ADD $32, R10 // i += 4 -> i +=32 - SUB $4, R3 // n -= 4 - BGE U4 // if n >= 0 goto U4 - -v4: - ADD $4, R3 // n += 4 - BLE E4 // if n <= 0 goto E4 - -L4: // n > 0 - MOVD 0(R8)(R10*1), R5 - ADDC R4, R5 - ADDE R0, R0 - MOVD R0, R4 // save CF - SUB R0, R0 - MOVD R5, 0(R2)(R10*1) - - ADD $8, R10 // i++ - SUB $1, R3 // n-- - BGT L4 // if n > 0 goto L4 - -E4: - MOVD R4, c+56(FP) // return c +// Update position of x(R6) and z(R8) based on the current counter value and perform copying. +// With the assumption that x and z will not overlap with each other or x and z will +// point to same memory region, we can use a faster version of copy using only MVC here. +// In the following implementation, we have three copy loops, each copying a word, 4 words, and +// 32 words at a time. Via benchmarking, this implementation is faster than calling runtime·memmove. +copySetup: + ADD R12, R6 + ADD R12, R8 + + CMPBGE R5, $4, mediumLoop + +smallLoop: // does a loop unrolling to copy word when n < 4 + CMPBEQ R5, $0, returnZero + MVC $8, 0(R6), 0(R8) + CMPBEQ R5, $1, returnZero + MVC $8, 8(R6), 8(R8) + CMPBEQ R5, $2, returnZero + MVC $8, 16(R6), 16(R8) + +returnZero: + MOVD $0, c+56(FP) // return 0 as carry + RET +mediumLoop: + CMPBLT R5, $4, smallLoop + CMPBLT R5, $32, mediumLoopBody + +largeLoop: // Copying 256 bytes at a time. + MVC $256, 0(R6), 0(R8) + MOVD $256(R6), R6 + MOVD $256(R8), R8 + MOVD $-32(R5), R5 + CMPBGE R5, $32, largeLoop + BR mediumLoop + +mediumLoopBody: // Copying 32 bytes at a time + MVC $32, 0(R6), 0(R8) + MOVD $32(R6), R6 + MOVD $32(R8), R8 + MOVD $-4(R5), R5 + CMPBGE R5, $4, mediumLoopBody + BR smallLoop + +returnC: + MOVD R7, c+56(FP) RET TEXT ·subVW(SB), NOSPLIT, $0 diff --git a/src/math/big/arith_s390x_test.go b/src/math/big/arith_s390x_test.go index eaf8f232e6fb1..e7f1b57ea580e 100644 --- a/src/math/big/arith_s390x_test.go +++ b/src/math/big/arith_s390x_test.go @@ -34,10 +34,7 @@ func TestFunVVnovec(t *testing.T) { func TestFunVWnovec(t *testing.T) { if hasVX == true { for _, a := range sumVW { - arg := a - testFunVW(t, "addVW_novec", addVW_novec, arg) - - arg = argVW{a.x, a.z, a.y, a.c} + arg := argVW{a.x, a.z, a.y, a.c} testFunVW(t, "subVW_novec", subVW_novec, arg) } }