cmd/compile: fold negation into addition/subtraction on arm64

Fold negation into addition/subtraction and avoid double negation.

platform: linux/arm64

file      before    after     Δ       %
addr2line 3628108   3628116   +8      +0.000%
asm       6208353   6207857   -496    -0.008%
buildid   3460682   3460418   -264    -0.008%
cgo       5572988   5572492   -496    -0.009%
compile   26042159  26041039  -1120   -0.004%
cover     6304328   6303472   -856    -0.014%
dist      4139330   4139098   -232    -0.006%
doc       9429305   9428065   -1240   -0.013%
fix       3997189   3996733   -456    -0.011%
link      8212128   8210280   -1848   -0.023%
nm        3620056   3619696   -360    -0.010%
objdump   5920289   5919233   -1056   -0.018%
pack      2892250   2891778   -472    -0.016%
pprof     17094569  17092745  -1824   -0.011%
test2json 3335825   3335529   -296    -0.009%
trace     15842080  15841456  -624    -0.004%
vet       9472194   9471106   -1088   -0.011%
go        19081541  19081509  -32     -0.000%
total     154253374 154240622 -12752  -0.008%

platform: darwin/arm64

file    before    after     Δ       %
compile 27152002  27135490  -16512  -0.061%
link    8372914   8356402   -16512  -0.197%
go      19154802  19154778  -24     -0.000%
total   157734180 157701132 -33048  -0.021%

Change-Id: I15a349bfbaf7333ec3e4a62ae4d06f3f371dfb1d
Reviewed-on: https://go-review.googlesource.com/c/go/+/673715
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: David Chase <drchase@google.com>
Auto-Submit: Keith Randall <khr@golang.org>
Reviewed-by: Keith Randall <khr@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

src/cmd/compile/internal/ssa/_gen/ARM64.rules

@@ -1198,6 +1198,7 @@
 
 // generic simplifications
 (ADD x (NEG y)) => (SUB x y)
+(SUB x (NEG y)) => (ADD x y)
 (SUB x x) => (MOVDconst [0])
 (AND x x) => x
 (OR  x x) => x
@@ -1209,6 +1210,7 @@
 (XOR x (MVN y)) => (EON x y)
 (OR  x (MVN y)) => (ORN x y)
 (MVN (XOR x y)) => (EON x y)
+(NEG (SUB x y)) => (SUB y x)
 (NEG (NEG x)) => x
 
 (CSEL [cc] (MOVDconst [-1]) (MOVDconst [0]) flag) => (CSETM [cc] flag)

src/cmd/compile/internal/ssa/rewriteARM64.go

@@ -12699,6 +12699,18 @@ func rewriteValueARM64_OpARM64NEG(v *Value) bool {
 		v.AddArg2(x, y)
 		return true
 	}
+	// match: (NEG (SUB x y))
+	// result: (SUB y x)
+	for {
+		if v_0.Op != OpARM64SUB {
+			break
+		}
+		y := v_0.Args[1]
+		x := v_0.Args[0]
+		v.reset(OpARM64SUB)
+		v.AddArg2(y, x)
+		return true
+	}
 	// match: (NEG (NEG x))
 	// result: x
 	for {
@@ -15204,6 +15216,18 @@ func rewriteValueARM64_OpARM64SUB(v *Value) bool {
 		v.AddArg(v0)
 		return true
 	}
+	// match: (SUB x (NEG y))
+	// result: (ADD x y)
+	for {
+		x := v_0
+		if v_1.Op != OpARM64NEG {
+			break
+		}
+		y := v_1.Args[0]
+		v.reset(OpARM64ADD)
+		v.AddArg2(x, y)
+		return true
+	}
 	// match: (SUB x x)
 	// result: (MOVDconst [0])
 	for {

test/codegen/arithmetic.go

@@ -91,6 +91,7 @@ func SubFromConst(a int) int {
 }
 
 func SubFromConstNeg(a int) int {
+	// arm64: "ADD\t\\$40"
 	// loong64: "ADDV[U]\t\\$40"
 	// mips: "ADD[U]\t\\$40"
 	// mips64: "ADDV[U]\t\\$40"
@@ -101,6 +102,7 @@ func SubFromConstNeg(a int) int {
 }
 
 func SubSubFromConst(a int) int {
+	// arm64: "ADD\t\\$20"
 	// loong64: "ADDV[U]\t\\$20"
 	// mips: "ADD[U]\t\\$20"
 	// mips64: "ADDV[U]\t\\$20"
@@ -118,6 +120,7 @@ func AddSubFromConst(a int) int {
 }
 
 func NegSubFromConst(a int) int {
+	// arm64: "SUB\t\\$20"
 	// loong64: "ADDV[U]\t\\$-20"
 	// mips: "ADD[U]\t\\$-20"
 	// mips64: "ADDV[U]\t\\$-20"
@@ -128,6 +131,7 @@ func NegSubFromConst(a int) int {
 }
 
 func NegAddFromConstNeg(a int) int {
+	// arm64: "SUB\t\\$40","NEG"
 	// loong64: "ADDV[U]\t\\$-40","SUBV"
 	// mips: "ADD[U]\t\\$-40","SUB"
 	// mips64: "ADDV[U]\t\\$-40","SUBV"
@@ -139,6 +143,7 @@ func NegAddFromConstNeg(a int) int {
 
 func SubSubNegSimplify(a, b int) int {
 	// amd64:"NEGQ"
+	// arm64:"NEG"
 	// loong64:"SUBV"
 	// mips:"SUB"
 	// mips64:"SUBV"
@@ -150,6 +155,7 @@ func SubSubNegSimplify(a, b int) int {
 
 func SubAddSimplify(a, b int) int {
 	// amd64:-"SUBQ",-"ADDQ"
+	// arm64:-"SUB",-"ADD"
 	// loong64:-"SUBV",-"ADDV"
 	// mips:-"SUB",-"ADD"
 	// mips64:-"SUBV",-"ADDV"
@@ -161,6 +167,7 @@ func SubAddSimplify(a, b int) int {
 
 func SubAddSimplify2(a, b, c int) (int, int, int, int, int, int) {
 	// amd64:-"ADDQ"
+	// arm64:-"ADD"
 	// mips:"SUB",-"ADD"
 	// mips64:"SUBV",-"ADDV"
 	// loong64:"SUBV",-"ADDV"
@@ -172,6 +179,7 @@ func SubAddSimplify2(a, b, c int) (int, int, int, int, int, int) {
 	// amd64:-"ADDQ"
 	r3 := (b + a) - (c + a)
 	// amd64:-"SUBQ"
+	// arm64:-"SUB"
 	// mips:"ADD",-"SUB"
 	// mips64:"ADDV",-"SUBV"
 	// loong64:"ADDV",-"SUBV"
@@ -183,6 +191,7 @@ func SubAddSimplify2(a, b, c int) (int, int, int, int, int, int) {
 
 func SubAddNegSimplify(a, b int) int {
 	// amd64:"NEGQ",-"ADDQ",-"SUBQ"
+	// arm64:"NEG",-"ADD",-"SUB"
 	// loong64:"SUBV",-"ADDV"
 	// mips:"SUB",-"ADD"
 	// mips64:"SUBV",-"ADDV"
@@ -194,6 +203,7 @@ func SubAddNegSimplify(a, b int) int {
 
 func AddAddSubSimplify(a, b, c int) int {
 	// amd64:-"SUBQ"
+	// arm64:"ADD",-"SUB"
 	// loong64:"ADDV",-"SUBV"
 	// mips:"ADD",-"SUB"
 	// mips64:"ADDV",-"SUBV"