mirror of
https://github.com/golang/go.git
synced 2025-05-28 10:51:22 +00:00
cmd/compile: optimize signed non-negative div/mod by a power of 2
This CL optimizes assembly for len() or cap() division
by a power of 2 constants:
func lenDiv(s []int) int {
return len(s) / 16
}
amd64 assembly before the CL:
MOVQ "".s+16(SP), AX
MOVQ AX, CX
SARQ $63, AX
SHRQ $60, AX
ADDQ CX, AX
SARQ $4, AX
MOVQ AX, "".~r1+32(SP)
RET
amd64 assembly after the CL:
MOVQ "".s+16(SP), AX
SHRQ $4, AX
MOVQ AX, "".~r1+32(SP)
RET
The CL relies on the fact that len() and cap() result cannot
be negative.
Trigger stats for the added SSA rules on linux/amd64 when running
make.bash:
46 Div64
12 Mod64
The added SSA rules may trigger on more cases in the future
when SSA values will be populated with the info on their
lower bounds.
For instance:
func f(i int16) int16 {
if i < 3 {
return -1
}
// Lower bound of i is 3 here -> i is non-negative,
// so unsigned arithmetics may be used here.
return i % 16
}
Change-Id: I8bc6be5a03e71157ced533c01416451ff6f1a7f0
Reviewed-on: https://go-review.googlesource.com/65530
Reviewed-by: Keith Randall <khr@golang.org>
This commit is contained in:
Aliaksandr Valialkin
Keith Randall
parent
2e8545531e
commit
0011cfbe2b
@ -1140,6 +1140,58 @@ var linuxAMD64Tests = []*asmTest{
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`,
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pos: []string{"\tSETHI\t\\("},
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},
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// Check that len() and cap() div by a constant power of two
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// are compiled into SHRQ.
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{
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fn: `
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func $(a []int) int {
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return len(a) / 1024
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}
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`,
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pos: []string{"\tSHRQ\t\\$10,"},
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},
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{
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fn: `
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func $(s string) int {
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return len(s) / (4097 >> 1)
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}
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`,
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pos: []string{"\tSHRQ\t\\$11,"},
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},
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{
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fn: `
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func $(a []int) int {
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return cap(a) / ((1 << 11) + 2048)
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}
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`,
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pos: []string{"\tSHRQ\t\\$12,"},
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},
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// Check that len() and cap() mod by a constant power of two
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// are compiled into ANDQ.
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{
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fn: `
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func $(a []int) int {
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return len(a) % 1024
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}
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`,
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pos: []string{"\tANDQ\t\\$1023,"},
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},
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{
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fn: `
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func $(s string) int {
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return len(s) % (4097 >> 1)
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}
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`,
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pos: []string{"\tANDQ\t\\$2047,"},
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},
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{
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fn: `
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func $(a []int) int {
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return cap(a) % ((1 << 11) + 2048)
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}
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`,
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pos: []string{"\tANDQ\t\\$4095,"},
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},
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}
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var linux386Tests = []*asmTest{
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@ -1219,6 +1271,58 @@ var linux386Tests = []*asmTest{
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}`,
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pos: []string{"\tADDL\t[$]-19", "\tIMULL"}, // (n-19)*a
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},
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// Check that len() and cap() div by a constant power of two
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// are compiled into SHRL.
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{
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fn: `
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func $(a []int) int {
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return len(a) / 1024
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}
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`,
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pos: []string{"\tSHRL\t\\$10,"},
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},
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{
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fn: `
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func $(s string) int {
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return len(s) / (4097 >> 1)
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}
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`,
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pos: []string{"\tSHRL\t\\$11,"},
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},
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{
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fn: `
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func $(a []int) int {
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return cap(a) / ((1 << 11) + 2048)
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}
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`,
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pos: []string{"\tSHRL\t\\$12,"},
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},
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// Check that len() and cap() mod by a constant power of two
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// are compiled into ANDL.
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{
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fn: `
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func $(a []int) int {
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return len(a) % 1024
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}
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`,
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pos: []string{"\tANDL\t\\$1023,"},
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},
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{
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fn: `
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func $(s string) int {
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return len(s) % (4097 >> 1)
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}
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`,
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pos: []string{"\tANDL\t\\$2047,"},
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},
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{
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fn: `
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func $(a []int) int {
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return cap(a) % ((1 << 11) + 2048)
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}
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`,
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pos: []string{"\tANDL\t\\$4095,"},
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},
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}
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var linuxS390XTests = []*asmTest{
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@ -1003,6 +1003,13 @@
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(Div64u n (Const64 [c])) && isPowerOfTwo(c) -> (Rsh64Ux64 n (Const64 <typ.UInt64> [log2(c)]))
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(Div64u n (Const64 [-1<<63])) -> (Rsh64Ux64 n (Const64 <typ.UInt64> [63]))
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// Signed non-negative divide by power of 2.
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(Div8 n (Const8 [c])) && isNonNegative(n) && isPowerOfTwo(c&0xff) -> (Rsh8Ux64 n (Const64 <typ.UInt64> [log2(c&0xff)]))
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(Div16 n (Const16 [c])) && isNonNegative(n) && isPowerOfTwo(c&0xffff) -> (Rsh16Ux64 n (Const64 <typ.UInt64> [log2(c&0xffff)]))
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(Div32 n (Const32 [c])) && isNonNegative(n) && isPowerOfTwo(c&0xffffffff) -> (Rsh32Ux64 n (Const64 <typ.UInt64> [log2(c&0xffffffff)]))
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(Div64 n (Const64 [c])) && isNonNegative(n) && isPowerOfTwo(c) -> (Rsh64Ux64 n (Const64 <typ.UInt64> [log2(c)]))
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(Div64 n (Const64 [-1<<63])) && isNonNegative(n) -> (Const64 [0])
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// Unsigned divide, not a power of 2. Strength reduce to a multiply.
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// For 8-bit divides, we just do a direct 9-bit by 8-bit multiply.
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(Div8u x (Const8 [c])) && umagicOK(8, c) ->
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@ -1236,6 +1243,13 @@
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(Mod64u <t> n (Const64 [c])) && isPowerOfTwo(c) -> (And64 n (Const64 <t> [c-1]))
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(Mod64u <t> n (Const64 [-1<<63])) -> (And64 n (Const64 <t> [1<<63-1]))
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// Signed non-negative mod by power of 2 constant.
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(Mod8 <t> n (Const8 [c])) && isNonNegative(n) && isPowerOfTwo(c&0xff) -> (And8 n (Const8 <t> [(c&0xff)-1]))
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(Mod16 <t> n (Const16 [c])) && isNonNegative(n) && isPowerOfTwo(c&0xffff) -> (And16 n (Const16 <t> [(c&0xffff)-1]))
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(Mod32 <t> n (Const32 [c])) && isNonNegative(n) && isPowerOfTwo(c&0xffffffff) -> (And32 n (Const32 <t> [(c&0xffffffff)-1]))
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(Mod64 <t> n (Const64 [c])) && isNonNegative(n) && isPowerOfTwo(c) -> (And64 n (Const64 <t> [c-1]))
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(Mod64 n (Const64 [-1<<63])) && isNonNegative(n) -> n
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// Signed mod by negative constant.
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(Mod8 <t> n (Const8 [c])) && c < 0 && c != -1<<7 -> (Mod8 <t> n (Const8 <t> [-c]))
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(Mod16 <t> n (Const16 [c])) && c < 0 && c != -1<<15 -> (Mod16 <t> n (Const16 <t> [-c]))
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@ -7266,6 +7266,27 @@ func rewriteValuegeneric_OpDiv16_0(v *Value) bool {
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v.AuxInt = int64(int16(c) / int16(d))
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return true
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}
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// match: (Div16 n (Const16 [c]))
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// cond: isNonNegative(n) && isPowerOfTwo(c&0xffff)
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// result: (Rsh16Ux64 n (Const64 <typ.UInt64> [log2(c&0xffff)]))
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for {
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_ = v.Args[1]
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n := v.Args[0]
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v_1 := v.Args[1]
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if v_1.Op != OpConst16 {
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break
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}
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c := v_1.AuxInt
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if !(isNonNegative(n) && isPowerOfTwo(c&0xffff)) {
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break
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}
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v.reset(OpRsh16Ux64)
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v.AddArg(n)
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v0 := b.NewValue0(v.Pos, OpConst64, typ.UInt64)
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v0.AuxInt = log2(c & 0xffff)
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v.AddArg(v0)
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return true
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}
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// match: (Div16 <t> n (Const16 [c]))
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// cond: c < 0 && c != -1<<15
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// result: (Neg16 (Div16 <t> n (Const16 <t> [-c])))
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@ -7609,6 +7630,27 @@ func rewriteValuegeneric_OpDiv32_0(v *Value) bool {
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v.AuxInt = int64(int32(c) / int32(d))
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return true
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}
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// match: (Div32 n (Const32 [c]))
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// cond: isNonNegative(n) && isPowerOfTwo(c&0xffffffff)
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// result: (Rsh32Ux64 n (Const64 <typ.UInt64> [log2(c&0xffffffff)]))
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for {
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_ = v.Args[1]
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n := v.Args[0]
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v_1 := v.Args[1]
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if v_1.Op != OpConst32 {
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break
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}
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c := v_1.AuxInt
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if !(isNonNegative(n) && isPowerOfTwo(c&0xffffffff)) {
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break
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}
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v.reset(OpRsh32Ux64)
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v.AddArg(n)
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v0 := b.NewValue0(v.Pos, OpConst64, typ.UInt64)
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v0.AuxInt = log2(c & 0xffffffff)
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v.AddArg(v0)
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return true
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}
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// match: (Div32 <t> n (Const32 [c]))
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// cond: c < 0 && c != -1<<31
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// result: (Neg32 (Div32 <t> n (Const32 <t> [-c])))
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@ -8130,6 +8172,47 @@ func rewriteValuegeneric_OpDiv64_0(v *Value) bool {
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v.AuxInt = c / d
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return true
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}
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// match: (Div64 n (Const64 [c]))
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// cond: isNonNegative(n) && isPowerOfTwo(c)
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// result: (Rsh64Ux64 n (Const64 <typ.UInt64> [log2(c)]))
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for {
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_ = v.Args[1]
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n := v.Args[0]
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v_1 := v.Args[1]
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if v_1.Op != OpConst64 {
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break
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}
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c := v_1.AuxInt
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if !(isNonNegative(n) && isPowerOfTwo(c)) {
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break
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}
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v.reset(OpRsh64Ux64)
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v.AddArg(n)
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v0 := b.NewValue0(v.Pos, OpConst64, typ.UInt64)
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v0.AuxInt = log2(c)
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v.AddArg(v0)
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return true
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}
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// match: (Div64 n (Const64 [-1<<63]))
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// cond: isNonNegative(n)
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// result: (Const64 [0])
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for {
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_ = v.Args[1]
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n := v.Args[0]
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v_1 := v.Args[1]
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if v_1.Op != OpConst64 {
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break
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}
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if v_1.AuxInt != -1<<63 {
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break
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}
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if !(isNonNegative(n)) {
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break
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}
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v.reset(OpConst64)
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v.AuxInt = 0
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return true
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}
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// match: (Div64 <t> n (Const64 [c]))
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// cond: c < 0 && c != -1<<63
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// result: (Neg64 (Div64 <t> n (Const64 <t> [-c])))
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@ -8526,6 +8609,27 @@ func rewriteValuegeneric_OpDiv8_0(v *Value) bool {
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v.AuxInt = int64(int8(c) / int8(d))
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return true
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}
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// match: (Div8 n (Const8 [c]))
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// cond: isNonNegative(n) && isPowerOfTwo(c&0xff)
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// result: (Rsh8Ux64 n (Const64 <typ.UInt64> [log2(c&0xff)]))
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for {
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_ = v.Args[1]
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n := v.Args[0]
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v_1 := v.Args[1]
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if v_1.Op != OpConst8 {
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break
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}
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c := v_1.AuxInt
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if !(isNonNegative(n) && isPowerOfTwo(c&0xff)) {
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break
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}
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v.reset(OpRsh8Ux64)
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v.AddArg(n)
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v0 := b.NewValue0(v.Pos, OpConst64, typ.UInt64)
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v0.AuxInt = log2(c & 0xff)
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v.AddArg(v0)
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return true
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}
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// match: (Div8 <t> n (Const8 [c]))
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// cond: c < 0 && c != -1<<7
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// result: (Neg8 (Div8 <t> n (Const8 <t> [-c])))
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@ -13476,6 +13580,28 @@ func rewriteValuegeneric_OpMod16_0(v *Value) bool {
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return true
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}
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// match: (Mod16 <t> n (Const16 [c]))
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// cond: isNonNegative(n) && isPowerOfTwo(c&0xffff)
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// result: (And16 n (Const16 <t> [(c&0xffff)-1]))
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for {
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t := v.Type
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_ = v.Args[1]
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n := v.Args[0]
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v_1 := v.Args[1]
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if v_1.Op != OpConst16 {
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break
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}
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c := v_1.AuxInt
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if !(isNonNegative(n) && isPowerOfTwo(c&0xffff)) {
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break
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}
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v.reset(OpAnd16)
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v.AddArg(n)
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v0 := b.NewValue0(v.Pos, OpConst16, t)
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v0.AuxInt = (c & 0xffff) - 1
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v.AddArg(v0)
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return true
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}
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// match: (Mod16 <t> n (Const16 [c]))
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// cond: c < 0 && c != -1<<15
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// result: (Mod16 <t> n (Const16 <t> [-c]))
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for {
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@ -13635,6 +13761,28 @@ func rewriteValuegeneric_OpMod32_0(v *Value) bool {
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return true
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}
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// match: (Mod32 <t> n (Const32 [c]))
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// cond: isNonNegative(n) && isPowerOfTwo(c&0xffffffff)
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// result: (And32 n (Const32 <t> [(c&0xffffffff)-1]))
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for {
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t := v.Type
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_ = v.Args[1]
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n := v.Args[0]
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v_1 := v.Args[1]
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if v_1.Op != OpConst32 {
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break
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}
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c := v_1.AuxInt
|
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if !(isNonNegative(n) && isPowerOfTwo(c&0xffffffff)) {
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break
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}
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v.reset(OpAnd32)
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v.AddArg(n)
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v0 := b.NewValue0(v.Pos, OpConst32, t)
|
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v0.AuxInt = (c & 0xffffffff) - 1
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v.AddArg(v0)
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return true
|
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}
|
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// match: (Mod32 <t> n (Const32 [c]))
|
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// cond: c < 0 && c != -1<<31
|
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// result: (Mod32 <t> n (Const32 <t> [-c]))
|
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for {
|
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@ -13794,6 +13942,49 @@ func rewriteValuegeneric_OpMod64_0(v *Value) bool {
|
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return true
|
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}
|
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// match: (Mod64 <t> n (Const64 [c]))
|
||||
// cond: isNonNegative(n) && isPowerOfTwo(c)
|
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// result: (And64 n (Const64 <t> [c-1]))
|
||||
for {
|
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t := v.Type
|
||||
_ = v.Args[1]
|
||||
n := v.Args[0]
|
||||
v_1 := v.Args[1]
|
||||
if v_1.Op != OpConst64 {
|
||||
break
|
||||
}
|
||||
c := v_1.AuxInt
|
||||
if !(isNonNegative(n) && isPowerOfTwo(c)) {
|
||||
break
|
||||
}
|
||||
v.reset(OpAnd64)
|
||||
v.AddArg(n)
|
||||
v0 := b.NewValue0(v.Pos, OpConst64, t)
|
||||
v0.AuxInt = c - 1
|
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v.AddArg(v0)
|
||||
return true
|
||||
}
|
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// match: (Mod64 n (Const64 [-1<<63]))
|
||||
// cond: isNonNegative(n)
|
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// result: n
|
||||
for {
|
||||
_ = v.Args[1]
|
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n := v.Args[0]
|
||||
v_1 := v.Args[1]
|
||||
if v_1.Op != OpConst64 {
|
||||
break
|
||||
}
|
||||
if v_1.AuxInt != -1<<63 {
|
||||
break
|
||||
}
|
||||
if !(isNonNegative(n)) {
|
||||
break
|
||||
}
|
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v.reset(OpCopy)
|
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v.Type = n.Type
|
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v.AddArg(n)
|
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return true
|
||||
}
|
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// match: (Mod64 <t> n (Const64 [c]))
|
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// cond: c < 0 && c != -1<<63
|
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// result: (Mod64 <t> n (Const64 <t> [-c]))
|
||||
for {
|
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@ -13974,6 +14165,28 @@ func rewriteValuegeneric_OpMod8_0(v *Value) bool {
|
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return true
|
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}
|
||||
// match: (Mod8 <t> n (Const8 [c]))
|
||||
// cond: isNonNegative(n) && isPowerOfTwo(c&0xff)
|
||||
// result: (And8 n (Const8 <t> [(c&0xff)-1]))
|
||||
for {
|
||||
t := v.Type
|
||||
_ = v.Args[1]
|
||||
n := v.Args[0]
|
||||
v_1 := v.Args[1]
|
||||
if v_1.Op != OpConst8 {
|
||||
break
|
||||
}
|
||||
c := v_1.AuxInt
|
||||
if !(isNonNegative(n) && isPowerOfTwo(c&0xff)) {
|
||||
break
|
||||
}
|
||||
v.reset(OpAnd8)
|
||||
v.AddArg(n)
|
||||
v0 := b.NewValue0(v.Pos, OpConst8, t)
|
||||
v0.AuxInt = (c & 0xff) - 1
|
||||
v.AddArg(v0)
|
||||
return true
|
||||
}
|
||||
// match: (Mod8 <t> n (Const8 [c]))
|
||||
// cond: c < 0 && c != -1<<7
|
||||
// result: (Mod8 <t> n (Const8 <t> [-c]))
|
||||
for {
|
||||
|
||||
Loading…
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Reference in New Issue
Block a user