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Revert "compile: prefer an AND instead of SHR+SHL instructions"

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This reverts commit 9ec7074a94.

Reason for revert: broke s390x (copysign, abs) and arm64 (bitfield) tests.

Change-Id: I16c1b389c062e8c4aa5de079f1d46c9b25b0db52
Reviewed-on: https://go-review.googlesource.com/c/go/+/193850
Run-TryBot: Martin Möhrmann <moehrmann@google.com>
Reviewed-by: Agniva De Sarker <agniva.quicksilver@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
This commit is contained in:
Martin Möhrmann 2019-09-09 07:22:14 +00:00
parent 9ec7074a94
commit 5bb59b6d16
4 changed files with 123 additions and 8 deletions
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5
src/cmd/compile/internal/ssa/gen/ARM64.rules
View File

@ -1863,8 +1863,9 @@
(XORshiftLL <t> [c] (UBFX [bfc] x) x2) && c < 32 && t.Size() == 4 && bfc == armBFAuxInt(32-c, c)
-> (EXTRWconst [32-c] x2 x)
// Rewrite special pairs of shifts to AND.
// On ARM64 the bitmask can fit into an instruction.
// Generic rules rewrite certain AND to a pair of shifts.
// However, on ARM64 the bitmask can fit into an instruction.
// Rewrite it back to AND.
(SRLconst [c] (SLLconst [c] x)) && 0 < c && c < 64 -> (ANDconst [1<<uint(64-c)-1] x) // mask out high bits
(SLLconst [c] (SRLconst [c] x)) && 0 < c && c < 64 -> (ANDconst [^(1<<uint(c)-1)] x) // mask out low bits

8
src/cmd/compile/internal/ssa/gen/generic.rules
View File

@ -542,6 +542,14 @@
(Slicemask (Const64 [x])) && x > 0 -> (Const64 [-1])
(Slicemask (Const64 [0])) -> (Const64 [0])
// Rewrite AND of consts as shifts if possible, slightly faster for 64 bit operands
// leading zeros can be shifted left, then right
(And64 <t> (Const64 [y]) x) && nlz(y) + nto(y) == 64 && nto(y) >= 32
-> (Rsh64Ux64 (Lsh64x64 <t> x (Const64 <t> [nlz(y)])) (Const64 <t> [nlz(y)]))
// trailing zeros can be shifted right, then left
(And64 <t> (Const64 [y]) x) && nlo(y) + ntz(y) == 64 && ntz(y) >= 32
-> (Lsh64x64 (Rsh64Ux64 <t> x (Const64 <t> [ntz(y)])) (Const64 <t> [ntz(y)]))
// simplifications often used for lengths. e.g. len(s[i:i+5])==5
(Sub(64|32|16|8) (Add(64|32|16|8) x y) x) -> y
(Sub(64|32|16|8) (Add(64|32|16|8) x y) y) -> x

114
src/cmd/compile/internal/ssa/rewritegeneric.go
View File

@ -5735,6 +5735,112 @@ func rewriteValuegeneric_OpAnd64_10(v *Value) bool {
v.AddArg(y)
return true
}
// match: (And64 <t> (Const64 [y]) x)
// cond: nlz(y) + nto(y) == 64 && nto(y) >= 32
// result: (Rsh64Ux64 (Lsh64x64 <t> x (Const64 <t> [nlz(y)])) (Const64 <t> [nlz(y)]))
for {
t := v.Type
x := v.Args[1]
v_0 := v.Args[0]
if v_0.Op != OpConst64 {
break
}
y := v_0.AuxInt
if !(nlz(y)+nto(y) == 64 && nto(y) >= 32) {
break
}
v.reset(OpRsh64Ux64)
v0 := b.NewValue0(v.Pos, OpLsh64x64, t)
v0.AddArg(x)
v1 := b.NewValue0(v.Pos, OpConst64, t)
v1.AuxInt = nlz(y)
v0.AddArg(v1)
v.AddArg(v0)
v2 := b.NewValue0(v.Pos, OpConst64, t)
v2.AuxInt = nlz(y)
v.AddArg(v2)
return true
}
// match: (And64 <t> x (Const64 [y]))
// cond: nlz(y) + nto(y) == 64 && nto(y) >= 32
// result: (Rsh64Ux64 (Lsh64x64 <t> x (Const64 <t> [nlz(y)])) (Const64 <t> [nlz(y)]))
for {
t := v.Type
_ = v.Args[1]
x := v.Args[0]
v_1 := v.Args[1]
if v_1.Op != OpConst64 {
break
}
y := v_1.AuxInt
if !(nlz(y)+nto(y) == 64 && nto(y) >= 32) {
break
}
v.reset(OpRsh64Ux64)
v0 := b.NewValue0(v.Pos, OpLsh64x64, t)
v0.AddArg(x)
v1 := b.NewValue0(v.Pos, OpConst64, t)
v1.AuxInt = nlz(y)
v0.AddArg(v1)
v.AddArg(v0)
v2 := b.NewValue0(v.Pos, OpConst64, t)
v2.AuxInt = nlz(y)
v.AddArg(v2)
return true
}
// match: (And64 <t> (Const64 [y]) x)
// cond: nlo(y) + ntz(y) == 64 && ntz(y) >= 32
// result: (Lsh64x64 (Rsh64Ux64 <t> x (Const64 <t> [ntz(y)])) (Const64 <t> [ntz(y)]))
for {
t := v.Type
x := v.Args[1]
v_0 := v.Args[0]
if v_0.Op != OpConst64 {
break
}
y := v_0.AuxInt
if !(nlo(y)+ntz(y) == 64 && ntz(y) >= 32) {
break
}
v.reset(OpLsh64x64)
v0 := b.NewValue0(v.Pos, OpRsh64Ux64, t)
v0.AddArg(x)
v1 := b.NewValue0(v.Pos, OpConst64, t)
v1.AuxInt = ntz(y)
v0.AddArg(v1)
v.AddArg(v0)
v2 := b.NewValue0(v.Pos, OpConst64, t)
v2.AuxInt = ntz(y)
v.AddArg(v2)
return true
}
// match: (And64 <t> x (Const64 [y]))
// cond: nlo(y) + ntz(y) == 64 && ntz(y) >= 32
// result: (Lsh64x64 (Rsh64Ux64 <t> x (Const64 <t> [ntz(y)])) (Const64 <t> [ntz(y)]))
for {
t := v.Type
_ = v.Args[1]
x := v.Args[0]
v_1 := v.Args[1]
if v_1.Op != OpConst64 {
break
}
y := v_1.AuxInt
if !(nlo(y)+ntz(y) == 64 && ntz(y) >= 32) {
break
}
v.reset(OpLsh64x64)
v0 := b.NewValue0(v.Pos, OpRsh64Ux64, t)
v0.AddArg(x)
v1 := b.NewValue0(v.Pos, OpConst64, t)
v1.AuxInt = ntz(y)
v0.AddArg(v1)
v.AddArg(v0)
v2 := b.NewValue0(v.Pos, OpConst64, t)
v2.AuxInt = ntz(y)
v.AddArg(v2)
return true
}
// match: (And64 (And64 i:(Const64 <t>) z) x)
// cond: (z.Op != OpConst64 && x.Op != OpConst64)
// result: (And64 i (And64 <t> z x))
@ -5761,6 +5867,10 @@ func rewriteValuegeneric_OpAnd64_10(v *Value) bool {
v.AddArg(v0)
return true
}
return false
}
func rewriteValuegeneric_OpAnd64_20(v *Value) bool {
b := v.Block
// match: (And64 (And64 z i:(Const64 <t>)) x)
// cond: (z.Op != OpConst64 && x.Op != OpConst64)
// result: (And64 i (And64 <t> z x))
@ -5874,10 +5984,6 @@ func rewriteValuegeneric_OpAnd64_10(v *Value) bool {
v.AddArg(x)
return true
}
return false
}
func rewriteValuegeneric_OpAnd64_20(v *Value) bool {
b := v.Block
// match: (And64 (Const64 <t> [c]) (And64 x (Const64 <t> [d])))
// cond:
// result: (And64 (Const64 <t> [c&d]) x)

4
test/codegen/math.go
View File

@ -81,7 +81,7 @@ func abs32(x float32) float32 {
// Check that it's using integer registers
func copysign(a, b, c float64) {
// amd64:"BTRQ\t[$]63","ANDQ","ORQ"
// amd64:"BTRQ\t[$]63","SHRQ\t[$]63","SHLQ\t[$]63","ORQ"
// s390x:"CPSDR",-"MOVD" (no integer load/store)
// ppc64:"FCPSGN"
// ppc64le:"FCPSGN"
@ -100,7 +100,7 @@ func copysign(a, b, c float64) {
// s390x:"LNDFR\t",-"MOVD\t" (no integer load/store)
sink64[2] = math.Float64frombits(math.Float64bits(a) | 1<<63)
// amd64:"ANDQ","ORQ"
// amd64:-"SHLQ\t[$]1",-"SHRQ\t[$]1","SHRQ\t[$]63","SHLQ\t[$]63","ORQ"
// s390x:"CPSDR\t",-"MOVD\t" (no integer load/store)
// ppc64:"FCPSGN"
// ppc64le:"FCPSGN"