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go/test/codegen/shift.go
Ubuntu 8fc043ccfa cmd/compile: optimize right shifts of int32 on riscv64 
The compiler is currently sign extending 32 bit signed integers to
64 bits before right shifting them using a 64 bit shift instruction.
There's no need to do this as RISC-V has instructions for right
shifting 32 bit signed values (sraw and sraiw) which sign extend
the result of the shift to 64 bits.  Change the compiler so that
it uses sraw and sraiw for shifts of signed 32 bit integers reducing
in most cases the number of instructions needed to perform the shift.

Here are some examples of code sequences that are changed by this
patch:

int32(a) >> 2

  before:

    sll     x5,x10,0x20
    sra     x10,x5,0x22

  after:

    sraw    x10,x10,0x2

int32(v) >> int(s)

  before:

    sext.w  x5,x10
    sltiu   x6,x11,64
    add     x6,x6,-1
    or      x6,x11,x6
    sra     x10,x5,x6

  after:

    sltiu   x5,x11,32
    add     x5,x5,-1
    or      x5,x11,x5
    sraw    x10,x10,x5

int32(v) >> (int(s) & 31)

  before:

    sext.w  x5,x10
    and     x6,x11,63
    sra     x10,x5,x6

after:

    and     x5,x11,31
    sraw    x10,x10,x5

int32(100) >> int(a)

  before:

    bltz    x10,<target address calls runtime.panicshift>
    sltiu   x5,x10,64
    add     x5,x5,-1
    or      x5,x10,x5
    li      x6,100
    sra     x10,x6,x5

  after:

    bltz    x10,<target address calls runtime.panicshift>
    sltiu   x5,x10,32
    add     x5,x5,-1
    or      x5,x10,x5
    li      x6,100
    sraw    x10,x6,x5

int32(v) >> (int(s) & 63)

  before:

    sext.w  x5,x10
    and     x6,x11,63
    sra     x10,x5,x6

  after:

    and     x5,x11,63
    sltiu   x6,x5,32
    add     x6,x6,-1
    or      x5,x5,x6
    sraw    x10,x10,x5

In most cases we eliminate one instruction.  In the case where
we shift a int32 constant by a variable the number of instructions
generated is identical.  A sra is simply replaced by a sraw.  In the
unusual case where we shift right by a variable anded with a constant
> 31 but < 64, we generate two additional instructions.  As this is
an unusual case we do not try to optimize for it.

Some improvements can be seen in some of the existing benchmarks,
notably in the utf8 package which performs right shifts of runes
which are signed 32 bit integers.

                      |  utf8-old   |              utf8-new            |
                      |   sec/op    |   sec/op     vs base             |
EncodeASCIIRune-4       17.68n ± 0%   17.67n ± 0%       ~ (p=0.312 n=10)
EncodeJapaneseRune-4    35.34n ± 0%   34.53n ± 1%  -2.31% (p=0.000 n=10)
AppendASCIIRune-4       3.213n ± 0%   3.213n ± 0%       ~ (p=0.318 n=10)
AppendJapaneseRune-4    36.14n ± 0%   35.35n ± 0%  -2.19% (p=0.000 n=10)
DecodeASCIIRune-4       28.11n ± 0%   27.36n ± 0%  -2.69% (p=0.000 n=10)
DecodeJapaneseRune-4    38.55n ± 0%   38.58n ± 0%       ~ (p=0.612 n=10)

Change-Id: I60a91cbede9ce65597571c7b7dd9943eeb8d3cc2
Reviewed-on: https://go-review.googlesource.com/c/go/+/535115
Run-TryBot: Joel Sing <joel@sing.id.au>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Joel Sing <joel@sing.id.au>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Reviewed-by: M Zhuo <mzh@golangcn.org>
Reviewed-by: David Chase <drchase@google.com>
2023-10-30 14:47:06 +00:00

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// asmcheck
// Copyright 2018 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.
package codegen
// ------------------ //
// constant shifts //
// ------------------ //
func lshConst64x64(v int64) int64 {
// ppc64x:"SLD"
// riscv64:"SLLI",-"AND",-"SLTIU"
return v << uint64(33)
}
func rshConst64Ux64(v uint64) uint64 {
// ppc64x:"SRD"
// riscv64:"SRLI\t",-"AND",-"SLTIU"
return v >> uint64(33)
}
func rshConst64x64(v int64) int64 {
// ppc64x:"SRAD"
// riscv64:"SRAI\t",-"OR",-"SLTIU"
return v >> uint64(33)
}
func lshConst32x64(v int32) int32 {
// ppc64x:"SLW"
// riscv64:"SLLI",-"AND",-"SLTIU", -"MOVW"
return v << uint64(29)
}
func rshConst32Ux64(v uint32) uint32 {
// ppc64x:"SRW"
// riscv64:"SRLIW",-"AND",-"SLTIU", -"MOVW"
return v >> uint64(29)
}
func rshConst32x64(v int32) int32 {
// ppc64x:"SRAW"
// riscv64:"SRAIW",-"OR",-"SLTIU", -"MOVW"
return v >> uint64(29)
}
func lshConst64x32(v int64) int64 {
// ppc64x:"SLD"
// riscv64:"SLLI",-"AND",-"SLTIU"
return v << uint32(33)
}
func rshConst64Ux32(v uint64) uint64 {
// ppc64x:"SRD"
// riscv64:"SRLI\t",-"AND",-"SLTIU"
return v >> uint32(33)
}
func rshConst64x32(v int64) int64 {
// ppc64x:"SRAD"
// riscv64:"SRAI\t",-"OR",-"SLTIU"
return v >> uint32(33)
}
// ------------------ //
// masked shifts //
// ------------------ //
func lshMask64x64(v int64, s uint64) int64 {
// arm64:"LSL",-"AND"
// ppc64x:"RLDICL",-"ORN",-"ISEL"
// riscv64:"SLL",-"AND\t",-"SLTIU"
// s390x:-"RISBGZ",-"AND",-"LOCGR"
return v << (s & 63)
}
func rshMask64Ux64(v uint64, s uint64) uint64 {
// arm64:"LSR",-"AND",-"CSEL"
// ppc64x:"RLDICL",-"ORN",-"ISEL"
// riscv64:"SRL\t",-"AND\t",-"SLTIU"
// s390x:-"RISBGZ",-"AND",-"LOCGR"
return v >> (s & 63)
}
func rshMask64x64(v int64, s uint64) int64 {
// arm64:"ASR",-"AND",-"CSEL"
// ppc64x:"RLDICL",-"ORN",-"ISEL"
// riscv64:"SRA\t",-"OR",-"SLTIU"
// s390x:-"RISBGZ",-"AND",-"LOCGR"
return v >> (s & 63)
}
func lshMask32x64(v int32, s uint64) int32 {
// arm64:"LSL",-"AND"
// ppc64x:"ISEL",-"ORN"
// riscv64:"SLL",-"AND\t",-"SLTIU"
// s390x:-"RISBGZ",-"AND",-"LOCGR"
return v << (s & 63)
}
func rshMask32Ux64(v uint32, s uint64) uint32 {
// arm64:"LSR",-"AND"
// ppc64x:"ISEL",-"ORN"
// riscv64:"SRLW","SLTIU","NEG","AND\t",-"SRL\t"
// s390x:-"RISBGZ",-"AND",-"LOCGR"
return v >> (s & 63)
}
func rsh5Mask32Ux64(v uint32, s uint64) uint32 {
// riscv64:"SRLW",-"AND\t",-"SLTIU",-"SRL\t"
return v >> (s & 31)
}
func rshMask32x64(v int32, s uint64) int32 {
// arm64:"ASR",-"AND"
// ppc64x:"ISEL",-"ORN"
// riscv64:"SRAW","OR","SLTIU"
// s390x:-"RISBGZ",-"AND",-"LOCGR"
return v >> (s & 63)
}
func rsh5Mask32x64(v int32, s uint64) int32 {
// riscv64:"SRAW",-"OR",-"SLTIU"
return v >> (s & 31)
}
func lshMask64x32(v int64, s uint32) int64 {
// arm64:"LSL",-"AND"
// ppc64x:"RLDICL",-"ORN"
// riscv64:"SLL",-"AND\t",-"SLTIU"
// s390x:-"RISBGZ",-"AND",-"LOCGR"
return v << (s & 63)
}
func rshMask64Ux32(v uint64, s uint32) uint64 {
// arm64:"LSR",-"AND",-"CSEL"
// ppc64x:"RLDICL",-"ORN"
// riscv64:"SRL\t",-"AND\t",-"SLTIU"
// s390x:-"RISBGZ",-"AND",-"LOCGR"
return v >> (s & 63)
}
func rshMask64x32(v int64, s uint32) int64 {
// arm64:"ASR",-"AND",-"CSEL"
// ppc64x:"RLDICL",-"ORN",-"ISEL"
// riscv64:"SRA\t",-"OR",-"SLTIU"
// s390x:-"RISBGZ",-"AND",-"LOCGR"
return v >> (s & 63)
}
func lshMask64x32Ext(v int64, s int32) int64 {
// ppc64x:"RLDICL",-"ORN",-"ISEL"
// riscv64:"SLL",-"AND\t",-"SLTIU"
// s390x:-"RISBGZ",-"AND",-"LOCGR"
return v << uint(s&63)
}
func rshMask64Ux32Ext(v uint64, s int32) uint64 {
// ppc64x:"RLDICL",-"ORN",-"ISEL"
// riscv64:"SRL\t",-"AND\t",-"SLTIU"
// s390x:-"RISBGZ",-"AND",-"LOCGR"
return v >> uint(s&63)
}
func rshMask64x32Ext(v int64, s int32) int64 {
// ppc64x:"RLDICL",-"ORN",-"ISEL"
// riscv64:"SRA\t",-"OR",-"SLTIU"
// s390x:-"RISBGZ",-"AND",-"LOCGR"
return v >> uint(s&63)
}
// --------------- //
// signed shifts //
// --------------- //
// We do want to generate a test + panicshift for these cases.
func lshSigned(v8 int8, v16 int16, v32 int32, v64 int64, x int) {
// amd64:"TESTB"
_ = x << v8
// amd64:"TESTW"
_ = x << v16
// amd64:"TESTL"
_ = x << v32
// amd64:"TESTQ"
_ = x << v64
}
// We want to avoid generating a test + panicshift for these cases.
func lshSignedMasked(v8 int8, v16 int16, v32 int32, v64 int64, x int) {
// amd64:-"TESTB"
_ = x << (v8 & 7)
// amd64:-"TESTW"
_ = x << (v16 & 15)
// amd64:-"TESTL"
_ = x << (v32 & 31)
// amd64:-"TESTQ"
_ = x << (v64 & 63)
}
// ------------------ //
// bounded shifts //
// ------------------ //
func lshGuarded64(v int64, s uint) int64 {
if s < 64 {
// riscv64:"SLL",-"AND",-"SLTIU"
// s390x:-"RISBGZ",-"AND",-"LOCGR"
// wasm:-"Select",-".*LtU"
// arm64:"LSL",-"CSEL"
return v << s
}
panic("shift too large")
}
func rshGuarded64U(v uint64, s uint) uint64 {
if s < 64 {
// riscv64:"SRL\t",-"AND",-"SLTIU"
// s390x:-"RISBGZ",-"AND",-"LOCGR"
// wasm:-"Select",-".*LtU"
// arm64:"LSR",-"CSEL"
return v >> s
}
panic("shift too large")
}
func rshGuarded64(v int64, s uint) int64 {
if s < 64 {
// riscv64:"SRA\t",-"OR",-"SLTIU"
// s390x:-"RISBGZ",-"AND",-"LOCGR"
// wasm:-"Select",-".*LtU"
// arm64:"ASR",-"CSEL"
return v >> s
}
panic("shift too large")
}
func provedUnsignedShiftLeft(val64 uint64, val32 uint32, val16 uint16, val8 uint8, shift int) (r1 uint64, r2 uint32, r3 uint16, r4 uint8) {
if shift >= 0 && shift < 64 {
// arm64:"LSL",-"CSEL"
r1 = val64 << shift
}
if shift >= 0 && shift < 32 {
// arm64:"LSL",-"CSEL"
r2 = val32 << shift
}
if shift >= 0 && shift < 16 {
// arm64:"LSL",-"CSEL"
r3 = val16 << shift
}
if shift >= 0 && shift < 8 {
// arm64:"LSL",-"CSEL"
r4 = val8 << shift
}
return r1, r2, r3, r4
}
func provedSignedShiftLeft(val64 int64, val32 int32, val16 int16, val8 int8, shift int) (r1 int64, r2 int32, r3 int16, r4 int8) {
if shift >= 0 && shift < 64 {
// arm64:"LSL",-"CSEL"
r1 = val64 << shift
}
if shift >= 0 && shift < 32 {
// arm64:"LSL",-"CSEL"
r2 = val32 << shift
}
if shift >= 0 && shift < 16 {
// arm64:"LSL",-"CSEL"
r3 = val16 << shift
}
if shift >= 0 && shift < 8 {
// arm64:"LSL",-"CSEL"
r4 = val8 << shift
}
return r1, r2, r3, r4
}
func provedUnsignedShiftRight(val64 uint64, val32 uint32, val16 uint16, val8 uint8, shift int) (r1 uint64, r2 uint32, r3 uint16, r4 uint8) {
if shift >= 0 && shift < 64 {
// arm64:"LSR",-"CSEL"
r1 = val64 >> shift
}
if shift >= 0 && shift < 32 {
// arm64:"LSR",-"CSEL"
r2 = val32 >> shift
}
if shift >= 0 && shift < 16 {
// arm64:"LSR",-"CSEL"
r3 = val16 >> shift
}
if shift >= 0 && shift < 8 {
// arm64:"LSR",-"CSEL"
r4 = val8 >> shift
}
return r1, r2, r3, r4
}
func provedSignedShiftRight(val64 int64, val32 int32, val16 int16, val8 int8, shift int) (r1 int64, r2 int32, r3 int16, r4 int8) {
if shift >= 0 && shift < 64 {
// arm64:"ASR",-"CSEL"
r1 = val64 >> shift
}
if shift >= 0 && shift < 32 {
// arm64:"ASR",-"CSEL"
r2 = val32 >> shift
}
if shift >= 0 && shift < 16 {
// arm64:"ASR",-"CSEL"
r3 = val16 >> shift
}
if shift >= 0 && shift < 8 {
// arm64:"ASR",-"CSEL"
r4 = val8 >> shift
}
return r1, r2, r3, r4
}
func checkUnneededTrunc(tab *[100000]uint32, d uint64, v uint32, h uint16, b byte) (uint32, uint64) {
// ppc64x:-".*RLWINM",-".*RLDICR",".*CLRLSLDI"
f := tab[byte(v)^b]
// ppc64x:-".*RLWINM",-".*RLDICR",".*CLRLSLDI"
f += tab[byte(v)&b]
// ppc64x:-".*RLWINM",-".*RLDICR",".*CLRLSLDI"
f += tab[byte(v)|b]
// ppc64x:-".*RLWINM",-".*RLDICR",".*CLRLSLDI"
f += tab[uint16(v)&h]
// ppc64x:-".*RLWINM",-".*RLDICR",".*CLRLSLDI"
f += tab[uint16(v)^h]
// ppc64x:-".*RLWINM",-".*RLDICR",".*CLRLSLDI"
f += tab[uint16(v)|h]
// ppc64x:-".*AND",-"RLDICR",".*CLRLSLDI"
f += tab[v&0xff]
// ppc64x:-".*AND",".*CLRLSLWI"
f += 2 * uint32(uint16(d))
// ppc64x:-".*AND",-"RLDICR",".*CLRLSLDI"
g := 2 * uint64(uint32(d))
return f, g
}
func checkCombinedShifts(v8 uint8, v16 uint16, v32 uint32, x32 int32, v64 uint64) (uint8, uint16, uint32, uint64, int64) {
// ppc64x:-"AND","CLRLSLWI"
f := (v8 & 0xF) << 2
// ppc64x:"CLRLSLWI"
f += byte(v16) << 3
// ppc64x:-"AND","CLRLSLWI"
g := (v16 & 0xFF) << 3
// ppc64x:-"AND","CLRLSLWI"
h := (v32 & 0xFFFFF) << 2
// ppc64x:"CLRLSLDI"
i := (v64 & 0xFFFFFFFF) << 5
// ppc64x:-"CLRLSLDI"
i += (v64 & 0xFFFFFFF) << 38
// ppc64x/power9:-"CLRLSLDI"
i += (v64 & 0xFFFF00) << 10
// ppc64x/power9:-"SLD","EXTSWSLI"
j := int64(x32+32) * 8
return f, g, h, i, j
}
func checkWidenAfterShift(v int64, u uint64) (int64, uint64) {
// ppc64x:-".*MOVW"
f := int32(v >> 32)
// ppc64x:".*MOVW"
f += int32(v >> 31)
// ppc64x:-".*MOVH"
g := int16(v >> 48)
// ppc64x:".*MOVH"
g += int16(v >> 30)
// ppc64x:-".*MOVH"
g += int16(f >> 16)
// ppc64x:-".*MOVB"
h := int8(v >> 56)
// ppc64x:".*MOVB"
h += int8(v >> 28)
// ppc64x:-".*MOVB"
h += int8(f >> 24)
// ppc64x:".*MOVB"
h += int8(f >> 16)
return int64(h), uint64(g)
}
func checkShiftAndMask32(v []uint32) {
i := 0
// ppc64x: "RLWNM\t[$]24, R[0-9]+, [$]12, [$]19, R[0-9]+"
v[i] = (v[i] & 0xFF00000) >> 8
i++
// ppc64x: "RLWNM\t[$]26, R[0-9]+, [$]22, [$]29, R[0-9]+"
v[i] = (v[i] & 0xFF00) >> 6
i++
// ppc64x: "MOVW\tR0"
v[i] = (v[i] & 0xFF) >> 8
i++
// ppc64x: "MOVW\tR0"
v[i] = (v[i] & 0xF000000) >> 28
i++
// ppc64x: "RLWNM\t[$]26, R[0-9]+, [$]24, [$]31, R[0-9]+"
v[i] = (v[i] >> 6) & 0xFF
i++
// ppc64x: "RLWNM\t[$]26, R[0-9]+, [$]12, [$]19, R[0-9]+"
v[i] = (v[i] >> 6) & 0xFF000
i++
// ppc64x: "MOVW\tR0"
v[i] = (v[i] >> 20) & 0xFF000
i++
// ppc64x: "MOVW\tR0"
v[i] = (v[i] >> 24) & 0xFF00
i++
}
func checkMergedShifts32(a [256]uint32, b [256]uint64, u uint32, v uint32) {
// ppc64x: -"CLRLSLDI", "RLWNM\t[$]10, R[0-9]+, [$]22, [$]29, R[0-9]+"
a[0] = a[uint8(v>>24)]
// ppc64x: -"CLRLSLDI", "RLWNM\t[$]11, R[0-9]+, [$]21, [$]28, R[0-9]+"
b[0] = b[uint8(v>>24)]
// ppc64x: -"CLRLSLDI", "RLWNM\t[$]15, R[0-9]+, [$]21, [$]28, R[0-9]+"
b[1] = b[(v>>20)&0xFF]
// ppc64x: -"SLD", "RLWNM\t[$]10, R[0-9]+, [$]22, [$]28, R[0-9]+"
b[2] = b[v>>25]
}
// 128 bit shifts
func check128bitShifts(x, y uint64, bits uint) (uint64, uint64) {
s := bits & 63
ŝ := (64 - bits) & 63
// check that the shift operation has two commas (three operands)
// amd64:"SHRQ.*,.*,"
shr := x>>s | y<<ŝ
// amd64:"SHLQ.*,.*,"
shl := x<<s | y>>ŝ
return shr, shl
}
func checkShiftToMask(u []uint64, s []int64) {
// amd64:-"SHR",-"SHL","ANDQ"
u[0] = u[0] >> 5 << 5
// amd64:-"SAR",-"SHL","ANDQ"
s[0] = s[0] >> 5 << 5
// amd64:-"SHR",-"SHL","ANDQ"
u[1] = u[1] << 5 >> 5
}
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