cmd/compile: add more Neg/Com optimizations

This is a grab-bag of minor optimizations.

While we're here, document the c != -(1<<31)
constraints better (#31888).

file    before    after     Δ       %
go      14669924  14665828  -4096   -0.028%
asm     4867088   4858896   -8192   -0.168%
compile 23988320  23984224  -4096   -0.017%
cover   5210856   5206760   -4096   -0.079%
link    6084376   6080280   -4096   -0.067%
total   132181084 132156508 -24576  -0.019%

file                                                      before    after     Δ       %
archive/tar.a                                             516708    516702    -6      -0.001%
bufio.a                                                   182200    181974    -226    -0.124%
bytes.a                                                   217624    216890    -734    -0.337%
cmd/compile/internal/gc.a                                 8865412   8865228   -184    -0.002%
cmd/compile/internal/ssa.a                                29921002  29933976  +12974  +0.043%
cmd/go/internal/modfetch/codehost.a                       530602    530430    -172    -0.032%
cmd/go/internal/modfetch.a                                679664    679578    -86     -0.013%
cmd/go/internal/modfile.a                                 411102    410928    -174    -0.042%
cmd/go/internal/test.a                                    315218    315126    -92     -0.029%
cmd/go/internal/tlog.a                                    183242    183256    +14     +0.008%
cmd/go/internal/txtar.a                                   23148     23060     -88     -0.380%
cmd/internal/bio.a                                        132064    132060    -4      -0.003%
cmd/internal/buildid.a                                    107174    107172    -2      -0.002%
cmd/internal/edit.a                                       33208     33354     +146    +0.440%
cmd/internal/obj/arm.a                                    416488    416432    -56     -0.013%
cmd/internal/obj/arm64.a                                  2772626   2772622   -4      -0.000%
cmd/internal/obj/x86.a                                    923186    923114    -72     -0.008%
cmd/internal/obj.a                                        679834    679836    +2      +0.000%
cmd/internal/objfile.a                                    358374    358372    -2      -0.001%
cmd/internal/test2json.a                                  67482     67434     -48     -0.071%
cmd/link/internal/ld.a                                    2836280   2836110   -170    -0.006%
cmd/link/internal/loadpe.a                                148234    147736    -498    -0.336%
cmd/link/internal/objfile.a                               144534    144434    -100    -0.069%
cmd/link/internal/ppc64.a                                 170876    170382    -494    -0.289%
cmd/vendor/github.com/google/pprof/internal/elfexec.a     49896     49892     -4      -0.008%
cmd/vendor/github.com/google/pprof/internal/graph.a       437478    437404    -74     -0.017%
cmd/vendor/github.com/google/pprof/profile.a              902040    902044    +4      +0.000%
cmd/vendor/github.com/ianlancetaylor/demangle.a           1217856   1217854   -2      -0.000%
cmd/vendor/golang.org/x/arch/x86/x86asm.a                 561332    560684    -648    -0.115%
cmd/vendor/golang.org/x/crypto/ssh/terminal.a             153788    153784    -4      -0.003%
cmd/vendor/golang.org/x/sys/unix.a                        1043894   1043814   -80     -0.008%
cmd/vendor/golang.org/x/tools/go/analysis/passes/printf.a 288458    288414    -44     -0.015%
compress/flate.a                                          369024    368132    -892    -0.242%
crypto/aes.a                                              109058    108968    -90     -0.083%
crypto/cipher.a                                           150410    150544    +134    +0.089%
crypto/elliptic.a                                         323572    323758    +186    +0.057%
crypto/md5.a                                              50868     50788     -80     -0.157%
crypto/rsa.a                                              195292    195214    -78     -0.040%
crypto/sha1.a                                             70936     70858     -78     -0.110%
crypto/sha256.a                                           75316     75236     -80     -0.106%
crypto/sha512.a                                           84846     84768     -78     -0.092%
crypto/subtle.a                                           6520      6514      -6      -0.092%
crypto/tls.a                                              1654916   1654852   -64     -0.004%
crypto/x509.a                                             888674    888638    -36     -0.004%
database/sql.a                                            730280    730198    -82     -0.011%
debug/gosym.a                                             184936    184862    -74     -0.040%
debug/macho.a                                             272138    272136    -2      -0.001%
debug/plan9obj.a                                          78444     78368     -76     -0.097%
encoding/base64.a                                         82126     81882     -244    -0.297%
encoding/binary.a                                         187196    187150    -46     -0.025%
encoding/gob.a                                            897868    897870    +2      +0.000%
encoding/json.a                                           659934    659832    -102    -0.015%
encoding/pem.a                                            59138     58870     -268    -0.453%
encoding/xml.a                                            694054    693300    -754    -0.109%
fmt.a                                                     484518    484196    -322    -0.066%
go/format.a                                               33962     33994     +32     +0.094%
go/printer.a                                              437132    437134    +2      +0.000%
go/scanner.a                                              141774    141772    -2      -0.001%
go/token.a                                                125130    125126    -4      -0.003%
go/types.a                                                2192086   2191994   -92     -0.004%
html/template.a                                           599038    598770    -268    -0.045%
html.a                                                    184842    184710    -132    -0.071%
image/draw.a                                              129592    129238    -354    -0.273%
image/gif.a                                               171824    171716    -108    -0.063%
image/internal/imageutil.a                                20282     19272     -1010   -4.980%
image/jpeg.a                                              275608    275114    -494    -0.179%
image/png.a                                               343416    343620    +204    +0.059%
image.a                                                   362244    362210    -34     -0.009%
index/suffixarray.a                                       113040    112954    -86     -0.076%
internal/trace.a                                          518972    518838    -134    -0.026%
math/big.a                                                1012670   1012354   -316    -0.031%
math.a                                                    219338    219334    -4      -0.002%
mime/multipart.a                                          178854    178502    -352    -0.197%
mime/quotedprintable.a                                    49226     48936     -290    -0.589%
net/http/cgi.a                                            172328    172324    -4      -0.002%
net/http.a                                                4000180   3999732   -448    -0.011%
net.a                                                     1858330   1858252   -78     -0.004%
path/filepath.a                                           107496    107498    +2      +0.002%
reflect.a                                                 1439776   1439994   +218    +0.015%
regexp/syntax.a                                           459430    459432    +2      +0.000%
regexp.a                                                  416394    416400    +6      +0.001%
runtime/debug.a                                           42106     42100     -6      -0.014%
runtime/pprof/internal/profile.a                          608718    608720    +2      +0.000%
runtime/pprof.a                                           355474    355476    +2      +0.001%
runtime.a                                                 3555748   3555796   +48     +0.001%
strconv.a                                                 294432    294410    -22     -0.007%
strings.a                                                 292148    292090    -58     -0.020%
syscall.a                                                 859682    859470    -212    -0.025%
text/tabwriter.a                                          65614     65148     -466    -0.710%
vendor/golang.org/x/crypto/chacha20poly1305.a             126736    126728    -8      -0.006%
vendor/golang.org/x/crypto/cryptobyte.a                   269112    269114    +2      +0.001%
vendor/golang.org/x/crypto/internal/chacha20.a            61842     61262     -580    -0.938%
vendor/golang.org/x/crypto/poly1305.a                     47410     47404     -6      -0.013%
vendor/golang.org/x/net/dns/dnsmessage.a                  628700    628012    -688    -0.109%
vendor/golang.org/x/net/idna.a                            237678    237826    +148    +0.062%
vendor/golang.org/x/net/route.a                           187852    187458    -394    -0.210%
vendor/golang.org/x/sys/unix.a                            1022426   1022348   -78     -0.008%
vendor/golang.org/x/text/transform.a                      117954    118104    +150    +0.127%
vendor/golang.org/x/text/unicode/bidi.a                   291398    291404    +6      +0.002%
vendor/golang.org/x/text/unicode/norm.a                   534640    534540    -100    -0.019%
total                                                     128945190 128945128 -62     -0.000%

Change-Id: I346dc31356d5ef7774b824cf202169610bd26432
Reviewed-on: https://go-review.googlesource.com/c/go/+/175778
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

src/cmd/compile/internal/ssa/gen/AMD64.rules

@@ -1453,6 +1453,7 @@
 // Remove redundant ops
 // Not in generic rules, because they may appear after lowering e. g. Slicemask
 (NEG(Q|L) (NEG(Q|L) x)) -> x
+(NEG(Q|L) s:(SUB(Q|L) x y)) && s.Uses == 1 -> (SUB(Q|L) y x)
 
 // Convert constant subtracts to constant adds
 (SUBQconst [c] x) && c != -(1<<31) -> (ADDQconst [-c] x)
@@ -1501,7 +1502,10 @@
 (ORL x x) -> x
 (XORQ x x) -> (MOVQconst [0])
 (XORL x x) -> (MOVLconst [0])
+
+// Fold NEG into ADDconst/MULconst. Take care to keep c in 32 bit range.
 (NEGQ (ADDQconst [c] (NEGQ x))) && c != -(1<<31) -> (ADDQconst [-c] x)
+(MULQconst [c] (NEGQ x)) && c != -(1<<31) -> (MULQconst [-c] x)
 
 // checking AND against 0.
 (CMPQconst (ANDQ x y) [0]) -> (TESTQ x y)

src/cmd/compile/internal/ssa/gen/generic.rules

@@ -490,7 +490,15 @@
 
 (Neg(64|32|16|8) (Sub(64|32|16|8) x y)) -> (Sub(64|32|16|8) y x)
 
+// ^(x-1) == ^x+1 == -x
 (Add(64|32|16|8) (Const(64|32|16|8) [1]) (Com(64|32|16|8) x)) -> (Neg(64|32|16|8) x)
+(Com(64|32|16|8) (Add(64|32|16|8) (Const(64|32|16|8) [-1]) x)) -> (Neg(64|32|16|8) x)
+
+// -(-x) == x
+(Neg(64|32|16|8) (Neg(64|32|16|8) x)) -> x
+
+// -^x == x+1
+(Neg(64|32|16|8) <t> (Com(64|32|16|8) x)) -> (Add(64|32|16|8) (Const(64|32|16|8) <t> [1]) x)
 
 (And(64|32|16|8) x (And(64|32|16|8) x y)) -> (And(64|32|16|8) x y)
 (Or(64|32|16|8) x (Or(64|32|16|8) x y)) -> (Or(64|32|16|8) x y)

src/cmd/compile/internal/ssa/rewriteAMD64.go

@@ -25491,6 +25491,24 @@ func rewriteValueAMD64_OpAMD64MULQconst_30(v *Value) bool {
 		v.AuxInt = c * d
 		return true
 	}
+	// match: (MULQconst [c] (NEGQ x))
+	// cond: c != -(1<<31)
+	// result: (MULQconst [-c] x)
+	for {
+		c := v.AuxInt
+		v_0 := v.Args[0]
+		if v_0.Op != OpAMD64NEGQ {
+			break
+		}
+		x := v_0.Args[0]
+		if !(c != -(1 << 31)) {
+			break
+		}
+		v.reset(OpAMD64MULQconst)
+		v.AuxInt = -c
+		v.AddArg(x)
+		return true
+	}
 	return false
 }
 func rewriteValueAMD64_OpAMD64MULSD_0(v *Value) bool {
@@ -25786,6 +25804,24 @@ func rewriteValueAMD64_OpAMD64NEGL_0(v *Value) bool {
 		v.AddArg(x)
 		return true
 	}
+	// match: (NEGL s:(SUBL x y))
+	// cond: s.Uses == 1
+	// result: (SUBL y x)
+	for {
+		s := v.Args[0]
+		if s.Op != OpAMD64SUBL {
+			break
+		}
+		y := s.Args[1]
+		x := s.Args[0]
+		if !(s.Uses == 1) {
+			break
+		}
+		v.reset(OpAMD64SUBL)
+		v.AddArg(y)
+		v.AddArg(x)
+		return true
+	}
 	// match: (NEGL (MOVLconst [c]))
 	// cond:
 	// result: (MOVLconst [int64(int32(-c))])
@@ -25816,6 +25852,24 @@ func rewriteValueAMD64_OpAMD64NEGQ_0(v *Value) bool {
 		v.AddArg(x)
 		return true
 	}
+	// match: (NEGQ s:(SUBQ x y))
+	// cond: s.Uses == 1
+	// result: (SUBQ y x)
+	for {
+		s := v.Args[0]
+		if s.Op != OpAMD64SUBQ {
+			break
+		}
+		y := s.Args[1]
+		x := s.Args[0]
+		if !(s.Uses == 1) {
+			break
+		}
+		v.reset(OpAMD64SUBQ)
+		v.AddArg(y)
+		v.AddArg(x)
+		return true
+	}
 	// match: (NEGQ (MOVQconst [c]))
 	// cond:
 	// result: (MOVQconst [-c])

src/cmd/compile/internal/ssa/rewritegeneric.go

@@ -6689,6 +6689,47 @@ func rewriteValuegeneric_OpCom16_0(v *Value) bool {
 		v.AuxInt = ^c
 		return true
 	}
+	// match: (Com16 (Add16 (Const16 [-1]) x))
+	// cond:
+	// result: (Neg16 x)
+	for {
+		v_0 := v.Args[0]
+		if v_0.Op != OpAdd16 {
+			break
+		}
+		x := v_0.Args[1]
+		v_0_0 := v_0.Args[0]
+		if v_0_0.Op != OpConst16 {
+			break
+		}
+		if v_0_0.AuxInt != -1 {
+			break
+		}
+		v.reset(OpNeg16)
+		v.AddArg(x)
+		return true
+	}
+	// match: (Com16 (Add16 x (Const16 [-1])))
+	// cond:
+	// result: (Neg16 x)
+	for {
+		v_0 := v.Args[0]
+		if v_0.Op != OpAdd16 {
+			break
+		}
+		_ = v_0.Args[1]
+		x := v_0.Args[0]
+		v_0_1 := v_0.Args[1]
+		if v_0_1.Op != OpConst16 {
+			break
+		}
+		if v_0_1.AuxInt != -1 {
+			break
+		}
+		v.reset(OpNeg16)
+		v.AddArg(x)
+		return true
+	}
 	return false
 }
 func rewriteValuegeneric_OpCom32_0(v *Value) bool {
@@ -6719,6 +6760,47 @@ func rewriteValuegeneric_OpCom32_0(v *Value) bool {
 		v.AuxInt = ^c
 		return true
 	}
+	// match: (Com32 (Add32 (Const32 [-1]) x))
+	// cond:
+	// result: (Neg32 x)
+	for {
+		v_0 := v.Args[0]
+		if v_0.Op != OpAdd32 {
+			break
+		}
+		x := v_0.Args[1]
+		v_0_0 := v_0.Args[0]
+		if v_0_0.Op != OpConst32 {
+			break
+		}
+		if v_0_0.AuxInt != -1 {
+			break
+		}
+		v.reset(OpNeg32)
+		v.AddArg(x)
+		return true
+	}
+	// match: (Com32 (Add32 x (Const32 [-1])))
+	// cond:
+	// result: (Neg32 x)
+	for {
+		v_0 := v.Args[0]
+		if v_0.Op != OpAdd32 {
+			break
+		}
+		_ = v_0.Args[1]
+		x := v_0.Args[0]
+		v_0_1 := v_0.Args[1]
+		if v_0_1.Op != OpConst32 {
+			break
+		}
+		if v_0_1.AuxInt != -1 {
+			break
+		}
+		v.reset(OpNeg32)
+		v.AddArg(x)
+		return true
+	}
 	return false
 }
 func rewriteValuegeneric_OpCom64_0(v *Value) bool {
@@ -6749,6 +6831,47 @@ func rewriteValuegeneric_OpCom64_0(v *Value) bool {
 		v.AuxInt = ^c
 		return true
 	}
+	// match: (Com64 (Add64 (Const64 [-1]) x))
+	// cond:
+	// result: (Neg64 x)
+	for {
+		v_0 := v.Args[0]
+		if v_0.Op != OpAdd64 {
+			break
+		}
+		x := v_0.Args[1]
+		v_0_0 := v_0.Args[0]
+		if v_0_0.Op != OpConst64 {
+			break
+		}
+		if v_0_0.AuxInt != -1 {
+			break
+		}
+		v.reset(OpNeg64)
+		v.AddArg(x)
+		return true
+	}
+	// match: (Com64 (Add64 x (Const64 [-1])))
+	// cond:
+	// result: (Neg64 x)
+	for {
+		v_0 := v.Args[0]
+		if v_0.Op != OpAdd64 {
+			break
+		}
+		_ = v_0.Args[1]
+		x := v_0.Args[0]
+		v_0_1 := v_0.Args[1]
+		if v_0_1.Op != OpConst64 {
+			break
+		}
+		if v_0_1.AuxInt != -1 {
+			break
+		}
+		v.reset(OpNeg64)
+		v.AddArg(x)
+		return true
+	}
 	return false
 }
 func rewriteValuegeneric_OpCom8_0(v *Value) bool {
@@ -6779,6 +6902,47 @@ func rewriteValuegeneric_OpCom8_0(v *Value) bool {
 		v.AuxInt = ^c
 		return true
 	}
+	// match: (Com8 (Add8 (Const8 [-1]) x))
+	// cond:
+	// result: (Neg8 x)
+	for {
+		v_0 := v.Args[0]
+		if v_0.Op != OpAdd8 {
+			break
+		}
+		x := v_0.Args[1]
+		v_0_0 := v_0.Args[0]
+		if v_0_0.Op != OpConst8 {
+			break
+		}
+		if v_0_0.AuxInt != -1 {
+			break
+		}
+		v.reset(OpNeg8)
+		v.AddArg(x)
+		return true
+	}
+	// match: (Com8 (Add8 x (Const8 [-1])))
+	// cond:
+	// result: (Neg8 x)
+	for {
+		v_0 := v.Args[0]
+		if v_0.Op != OpAdd8 {
+			break
+		}
+		_ = v_0.Args[1]
+		x := v_0.Args[0]
+		v_0_1 := v_0.Args[1]
+		if v_0_1.Op != OpConst8 {
+			break
+		}
+		if v_0_1.AuxInt != -1 {
+			break
+		}
+		v.reset(OpNeg8)
+		v.AddArg(x)
+		return true
+	}
 	return false
 }
 func rewriteValuegeneric_OpConstInterface_0(v *Value) bool {
@@ -36629,6 +36793,7 @@ func rewriteValuegeneric_OpMul8_10(v *Value) bool {
 	return false
 }
 func rewriteValuegeneric_OpNeg16_0(v *Value) bool {
+	b := v.Block
 	// match: (Neg16 (Const16 [c]))
 	// cond:
 	// result: (Const16 [int64(-int16(c))])
@@ -36657,9 +36822,41 @@ func rewriteValuegeneric_OpNeg16_0(v *Value) bool {
 		v.AddArg(x)
 		return true
 	}
+	// match: (Neg16 (Neg16 x))
+	// cond:
+	// result: x
+	for {
+		v_0 := v.Args[0]
+		if v_0.Op != OpNeg16 {
+			break
+		}
+		x := v_0.Args[0]
+		v.reset(OpCopy)
+		v.Type = x.Type
+		v.AddArg(x)
+		return true
+	}
+	// match: (Neg16 <t> (Com16 x))
+	// cond:
+	// result: (Add16 (Const16 <t> [1]) x)
+	for {
+		t := v.Type
+		v_0 := v.Args[0]
+		if v_0.Op != OpCom16 {
+			break
+		}
+		x := v_0.Args[0]
+		v.reset(OpAdd16)
+		v0 := b.NewValue0(v.Pos, OpConst16, t)
+		v0.AuxInt = 1
+		v.AddArg(v0)
+		v.AddArg(x)
+		return true
+	}
 	return false
 }
 func rewriteValuegeneric_OpNeg32_0(v *Value) bool {
+	b := v.Block
 	// match: (Neg32 (Const32 [c]))
 	// cond:
 	// result: (Const32 [int64(-int32(c))])
@@ -36688,6 +36885,37 @@ func rewriteValuegeneric_OpNeg32_0(v *Value) bool {
 		v.AddArg(x)
 		return true
 	}
+	// match: (Neg32 (Neg32 x))
+	// cond:
+	// result: x
+	for {
+		v_0 := v.Args[0]
+		if v_0.Op != OpNeg32 {
+			break
+		}
+		x := v_0.Args[0]
+		v.reset(OpCopy)
+		v.Type = x.Type
+		v.AddArg(x)
+		return true
+	}
+	// match: (Neg32 <t> (Com32 x))
+	// cond:
+	// result: (Add32 (Const32 <t> [1]) x)
+	for {
+		t := v.Type
+		v_0 := v.Args[0]
+		if v_0.Op != OpCom32 {
+			break
+		}
+		x := v_0.Args[0]
+		v.reset(OpAdd32)
+		v0 := b.NewValue0(v.Pos, OpConst32, t)
+		v0.AuxInt = 1
+		v.AddArg(v0)
+		v.AddArg(x)
+		return true
+	}
 	return false
 }
 func rewriteValuegeneric_OpNeg32F_0(v *Value) bool {
@@ -36710,6 +36938,7 @@ func rewriteValuegeneric_OpNeg32F_0(v *Value) bool {
 	return false
 }
 func rewriteValuegeneric_OpNeg64_0(v *Value) bool {
+	b := v.Block
 	// match: (Neg64 (Const64 [c]))
 	// cond:
 	// result: (Const64 [-c])
@@ -36738,6 +36967,37 @@ func rewriteValuegeneric_OpNeg64_0(v *Value) bool {
 		v.AddArg(x)
 		return true
 	}
+	// match: (Neg64 (Neg64 x))
+	// cond:
+	// result: x
+	for {
+		v_0 := v.Args[0]
+		if v_0.Op != OpNeg64 {
+			break
+		}
+		x := v_0.Args[0]
+		v.reset(OpCopy)
+		v.Type = x.Type
+		v.AddArg(x)
+		return true
+	}
+	// match: (Neg64 <t> (Com64 x))
+	// cond:
+	// result: (Add64 (Const64 <t> [1]) x)
+	for {
+		t := v.Type
+		v_0 := v.Args[0]
+		if v_0.Op != OpCom64 {
+			break
+		}
+		x := v_0.Args[0]
+		v.reset(OpAdd64)
+		v0 := b.NewValue0(v.Pos, OpConst64, t)
+		v0.AuxInt = 1
+		v.AddArg(v0)
+		v.AddArg(x)
+		return true
+	}
 	return false
 }
 func rewriteValuegeneric_OpNeg64F_0(v *Value) bool {
@@ -36760,6 +37020,7 @@ func rewriteValuegeneric_OpNeg64F_0(v *Value) bool {
 	return false
 }
 func rewriteValuegeneric_OpNeg8_0(v *Value) bool {
+	b := v.Block
 	// match: (Neg8 (Const8 [c]))
 	// cond:
 	// result: (Const8 [int64( -int8(c))])
@@ -36788,6 +37049,37 @@ func rewriteValuegeneric_OpNeg8_0(v *Value) bool {
 		v.AddArg(x)
 		return true
 	}
+	// match: (Neg8 (Neg8 x))
+	// cond:
+	// result: x
+	for {
+		v_0 := v.Args[0]
+		if v_0.Op != OpNeg8 {
+			break
+		}
+		x := v_0.Args[0]
+		v.reset(OpCopy)
+		v.Type = x.Type
+		v.AddArg(x)
+		return true
+	}
+	// match: (Neg8 <t> (Com8 x))
+	// cond:
+	// result: (Add8 (Const8 <t> [1]) x)
+	for {
+		t := v.Type
+		v_0 := v.Args[0]
+		if v_0.Op != OpCom8 {
+			break
+		}
+		x := v_0.Args[0]
+		v.reset(OpAdd8)
+		v0 := b.NewValue0(v.Pos, OpConst8, t)
+		v0.AuxInt = 1
+		v.AddArg(v0)
+		v.AddArg(x)
+		return true
+	}
 	return false
 }
 func rewriteValuegeneric_OpNeq16_0(v *Value) bool {