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cmd/compile: simplify slice/array range loops for some element sizes
In range loops over slices and arrays besides a variable to track the index an extra variable containing the address of the current element is used. To compute a pointer to the next element the elements size is added to the address. On 386 and amd64 an element of size 1, 2, 4 or 8 bytes can by copied from an array using a MOV instruction with suitable addressing mode that uses the start address of the array, the index of the element and element size as scaling factor. Thereby, for arrays and slices with suitable element size we can avoid keeping and incrementing an extra variable to compute the next elements address. Shrinks cmd/go by 4 kilobytes. AMD64: name old time/op new time/op delta BinaryTree17 2.66s ± 7% 2.54s ± 0% -4.53% (p=0.000 n=10+8) Fannkuch11 3.02s ± 1% 3.02s ± 1% ~ (p=0.579 n=10+10) FmtFprintfEmpty 45.6ns ± 1% 42.2ns ± 1% -7.46% (p=0.000 n=10+10) FmtFprintfString 69.8ns ± 1% 70.4ns ± 1% +0.84% (p=0.041 n=10+10) FmtFprintfInt 80.1ns ± 1% 79.0ns ± 1% -1.35% (p=0.000 n=10+10) FmtFprintfIntInt 127ns ± 1% 125ns ± 1% -1.00% (p=0.007 n=10+9) FmtFprintfPrefixedInt 158ns ± 2% 152ns ± 1% -4.11% (p=0.000 n=10+10) FmtFprintfFloat 218ns ± 1% 214ns ± 1% -1.61% (p=0.000 n=10+10) FmtManyArgs 508ns ± 1% 504ns ± 1% -0.93% (p=0.001 n=9+10) GobDecode 6.76ms ± 1% 6.78ms ± 1% ~ (p=0.353 n=10+10) GobEncode 5.84ms ± 1% 5.77ms ± 1% -1.31% (p=0.000 n=10+9) Gzip 223ms ± 1% 218ms ± 1% -2.39% (p=0.000 n=10+10) Gunzip 40.3ms ± 1% 40.4ms ± 3% ~ (p=0.796 n=10+10) HTTPClientServer 73.5µs ± 0% 73.3µs ± 0% -0.28% (p=0.000 n=10+9) JSONEncode 12.7ms ± 1% 12.6ms ± 8% ~ (p=0.173 n=8+10) JSONDecode 57.5ms ± 1% 56.1ms ± 2% -2.40% (p=0.000 n=10+10) Mandelbrot200 3.80ms ± 1% 3.86ms ± 6% ~ (p=0.579 n=10+10) GoParse 3.25ms ± 1% 3.23ms ± 1% ~ (p=0.052 n=10+10) RegexpMatchEasy0_32 74.4ns ± 1% 76.9ns ± 1% +3.39% (p=0.000 n=10+10) RegexpMatchEasy0_1K 243ns ± 2% 248ns ± 1% +1.86% (p=0.000 n=10+8) RegexpMatchEasy1_32 71.0ns ± 2% 72.8ns ± 1% +2.55% (p=0.000 n=10+10) RegexpMatchEasy1_1K 370ns ± 1% 383ns ± 0% +3.39% (p=0.000 n=10+9) RegexpMatchMedium_32 107ns ± 0% 113ns ± 1% +5.33% (p=0.000 n=6+10) RegexpMatchMedium_1K 35.0µs ± 1% 36.0µs ± 1% +3.13% (p=0.000 n=10+10) RegexpMatchHard_32 1.65µs ± 1% 1.69µs ± 1% +2.23% (p=0.000 n=10+9) RegexpMatchHard_1K 49.8µs ± 1% 50.6µs ± 1% +1.59% (p=0.000 n=10+10) Revcomp 398ms ± 1% 396ms ± 1% -0.51% (p=0.043 n=10+10) Template 63.4ms ± 1% 60.8ms ± 0% -4.11% (p=0.000 n=10+9) TimeParse 318ns ± 1% 322ns ± 1% +1.10% (p=0.005 n=10+10) TimeFormat 323ns ± 1% 336ns ± 1% +4.15% (p=0.000 n=10+10) Updates: #15809. Change-Id: I55915aaf6d26768e12247f8a8edf14e7630726d1 Reviewed-on: https://go-review.googlesource.com/38061 Run-TryBot: Martin Möhrmann <moehrmann@google.com> Reviewed-by: Keith Randall <khr@golang.org>
This commit is contained in:
Martin Möhrmann
David Chase
parent
af40cbe83c
commit
743117a85e
@ -7,6 +7,7 @@ package gc
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import (
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"cmd/compile/internal/types"
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"cmd/internal/objabi"
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"cmd/internal/sys"
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"unicode/utf8"
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)
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@ -137,6 +138,22 @@ out:
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decldepth--
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}
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func cheapComputableIndex(width int64) bool {
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switch thearch.LinkArch.Family {
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// MIPS does not have R+R addressing
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// Arm64 may lack ability to generate this code in our assembler,
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// but the architecture supports it.
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case sys.PPC64, sys.S390X:
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return width == 1
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case sys.AMD64, sys.I386, sys.ARM64, sys.ARM:
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switch width {
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case 1, 2, 4, 8:
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return true
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}
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}
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return false
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}
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// walkrange transforms various forms of ORANGE into
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// simpler forms. The result must be assigned back to n.
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// Node n may also be modified in place, and may also be
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@ -202,57 +219,76 @@ func walkrange(n *Node) *Node {
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hv1 := temp(types.Types[TINT])
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hn := temp(types.Types[TINT])
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var hp *Node
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init = append(init, nod(OAS, hv1, nil))
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init = append(init, nod(OAS, hn, nod(OLEN, ha, nil)))
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if v2 != nil {
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hp = temp(types.NewPtr(n.Type.Elem()))
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tmp := nod(OINDEX, ha, nodintconst(0))
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tmp.SetBounded(true)
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init = append(init, nod(OAS, hp, nod(OADDR, tmp, nil)))
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}
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n.Left = nod(OLT, hv1, hn)
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n.Right = nod(OAS, hv1, nod(OADD, hv1, nodintconst(1)))
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if v1 == nil {
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body = nil
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} else if v2 == nil {
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body = []*Node{nod(OAS, v1, hv1)}
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} else { // for i,a := range thing { body }
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if objabi.Preemptibleloops_enabled != 0 {
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// Doing this transformation makes a bounds check removal less trivial; see #20711
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// TODO enhance the preemption check insertion so that this transformation is not necessary.
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ifGuard = nod(OIF, nil, nil)
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ifGuard.Left = nod(OLT, hv1, hn)
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translatedLoopOp = OFORUNTIL
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}
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// for range ha { body }
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if v1 == nil {
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break
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}
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// for v1 := range ha { body }
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if v2 == nil {
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body = []*Node{nod(OAS, v1, hv1)}
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break
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}
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// for v1, v2 := range ha { body }
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if cheapComputableIndex(n.Type.Elem().Width) {
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// v1, v2 = hv1, ha[hv1]
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tmp := nod(OINDEX, ha, hv1)
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tmp.SetBounded(true)
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// Use OAS2 to correctly handle assignments
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// of the form "v1, a[v1] := range".
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a := nod(OAS2, nil, nil)
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a.List.Set2(v1, v2)
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a.Rlist.Set2(hv1, nod(OIND, hp, nil))
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a.Rlist.Set2(hv1, tmp)
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body = []*Node{a}
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// Advance pointer as part of increment.
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// We used to advance the pointer before executing the loop body,
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// but doing so would make the pointer point past the end of the
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// array during the final iteration, possibly causing another unrelated
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// piece of memory not to be garbage collected until the loop finished.
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// Advancing during the increment ensures that the pointer p only points
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// pass the end of the array during the final "p++; i++; if(i >= len(x)) break;",
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// after which p is dead, so it cannot confuse the collector.
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tmp := nod(OADD, hp, nodintconst(t.Elem().Width))
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tmp.Type = hp.Type
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tmp.SetTypecheck(1)
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tmp.Right.Type = types.Types[types.Tptr]
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tmp.Right.SetTypecheck(1)
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a = nod(OAS, hp, tmp)
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a = typecheck(a, Etop)
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n.Right.Ninit.Set1(a)
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break
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}
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if objabi.Preemptibleloops_enabled != 0 {
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// Doing this transformation makes a bounds check removal less trivial; see #20711
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// TODO enhance the preemption check insertion so that this transformation is not necessary.
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ifGuard = nod(OIF, nil, nil)
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ifGuard.Left = nod(OLT, hv1, hn)
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translatedLoopOp = OFORUNTIL
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}
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hp := temp(types.NewPtr(n.Type.Elem()))
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tmp := nod(OINDEX, ha, nodintconst(0))
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tmp.SetBounded(true)
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init = append(init, nod(OAS, hp, nod(OADDR, tmp, nil)))
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// Use OAS2 to correctly handle assignments
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// of the form "v1, a[v1] := range".
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a := nod(OAS2, nil, nil)
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a.List.Set2(v1, v2)
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a.Rlist.Set2(hv1, nod(OIND, hp, nil))
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body = append(body, a)
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// Advance pointer as part of increment.
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// We used to advance the pointer before executing the loop body,
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// but doing so would make the pointer point past the end of the
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// array during the final iteration, possibly causing another unrelated
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// piece of memory not to be garbage collected until the loop finished.
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// Advancing during the increment ensures that the pointer p only points
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// pass the end of the array during the final "p++; i++; if(i >= len(x)) break;",
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// after which p is dead, so it cannot confuse the collector.
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tmp = nod(OADD, hp, nodintconst(t.Elem().Width))
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tmp.Type = hp.Type
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tmp.SetTypecheck(1)
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tmp.Right.Type = types.Types[types.Tptr]
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tmp.Right.SetTypecheck(1)
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a = nod(OAS, hp, tmp)
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a = typecheck(a, Etop)
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n.Right.Ninit.Set1(a)
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case TMAP:
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// orderstmt allocated the iterator for us.
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// we only use a once, so no copy needed.
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26
test/live.go
26
test/live.go
@ -463,22 +463,30 @@ func f29(b bool) {
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}
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// copy of array of pointers should die at end of range loop
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var pstructarr [10]pstruct
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var ptrarr [10]*int
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// Struct size choosen to make pointer to element in pstructarr
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// not computable by strength reduction.
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type pstruct struct {
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intp *int
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_ [8]byte
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}
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func f30(b bool) {
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// two live temps during print(p):
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// the copy of ptrarr and the internal iterator pointer.
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// two live temps during printintpointer(p):
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// in the copy of p.intp and
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// the internal iterator pointer if a pointer to pstruct in pstructarr
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// can not be easily computed by strength reduction.
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if b {
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for _, p := range ptrarr {
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printintpointer(p) // ERROR "live at call to printintpointer: .autotmp_[0-9]+ .autotmp_[0-9]+$"
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for _, p := range pstructarr {
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printintpointer(p.intp) // ERROR "live at call to printintpointer: .autotmp_[0-9]+ .autotmp_[0-9]+$"
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}
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}
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for _, p := range ptrarr {
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printintpointer(p) // ERROR "live at call to printintpointer: .autotmp_[0-9]+ .autotmp_[0-9]+$"
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for _, p := range pstructarr {
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printintpointer(p.intp) // ERROR "live at call to printintpointer: .autotmp_[0-9]+ .autotmp_[0-9]+$"
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}
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for _, p := range ptrarr {
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printintpointer(p) // ERROR "live at call to printintpointer: .autotmp_[0-9]+ .autotmp_[0-9]+$"
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for _, p := range pstructarr {
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printintpointer(p.intp) // ERROR "live at call to printintpointer: .autotmp_[0-9]+ .autotmp_[0-9]+$"
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}
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}
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