cmd/compile: defer lowering OANDNOT until SSA

Currently, "x &^ y" gets rewriten into "x & ^y" during walk. It adds
unnecessary complexity to other parts, which must aware about this.

Instead, we can just implement "&^" in the conversion to SSA, so "&^"
can be handled like other binary operators.

However, this CL does not pass toolstash-check. It seems that implements
"&^" in the conversion to SSA causes registers allocation change.

With the parent:

obj: 00212 (.../src/runtime/complex.go:47)    MOVQ    X0, AX
obj: 00213 (.../src/runtime/complex.go:47)    BTRQ    $63, AX
obj: 00214 (.../src/runtime/complex.go:47)    MOVQ    "".n(SP), CX
obj: 00215 (.../src/runtime/complex.go:47)    MOVQ    $-9223372036854775808, DX
obj: 00216 (.../src/runtime/complex.go:47)    ANDQ    DX, CX
obj: 00217 (.../src/runtime/complex.go:47)    ORQ AX, CX

With this CL:

obj: 00212 (.../src/runtime/complex.go:47)    MOVQ    X0, AX
obj: 00213 (.../src/runtime/complex.go:47)    BTRQ    $63, AX
obj: 00214 (.../src/runtime/complex.go:47)    MOVQ    $-9223372036854775808, CX
obj: 00215 (.../src/runtime/complex.go:47)    MOVQ    "".n(SP), DX
obj: 00216 (.../src/runtime/complex.go:47)    ANDQ    CX, DX
obj: 00217 (.../src/runtime/complex.go:47)    ORQ AX, DX

Change-Id: I80acf8496a91be4804fb7ef3df04c19baae2754c
Reviewed-on: https://go-review.googlesource.com/c/go/+/264660
Trust: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Run-TryBot: Cuong Manh Le <cuong.manhle.vn@gmail.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

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

@@ -2472,6 +2472,11 @@ func (s *state) expr(n *Node) *ssa.Value {
 		a := s.expr(n.Left)
 		b := s.expr(n.Right)
 		return s.newValue2(s.ssaOp(n.Op, n.Type), a.Type, a, b)
+	case OANDNOT:
+		a := s.expr(n.Left)
+		b := s.expr(n.Right)
+		b = s.newValue1(s.ssaOp(OBITNOT, b.Type), b.Type, b)
+		return s.newValue2(s.ssaOp(OAND, n.Type), a.Type, a, b)
 	case OLSH, ORSH:
 		a := s.expr(n.Left)
 		b := s.expr(n.Right)

src/cmd/compile/internal/gc/syntax.go

@@ -142,7 +142,7 @@ const (
 	_, _                               // second nodeInitorder bit
 	_, nodeHasBreak
 	_, nodeNoInline  // used internally by inliner to indicate that a function call should not be inlined; set for OCALLFUNC and OCALLMETH only
-	_, nodeImplicit  // implicit OADDR or ODEREF; ++/-- statement represented as OASOP; or ANDNOT lowered to OAND
+	_, nodeImplicit  // implicit OADDR or ODEREF; ++/-- statement represented as OASOP
 	_, nodeIsDDD     // is the argument variadic
 	_, nodeDiag      // already printed error about this
 	_, nodeColas     // OAS resulting from :=

src/cmd/compile/internal/gc/walk.go

@@ -474,7 +474,7 @@ opswitch:
 		ODEREF, OSPTR, OITAB, OIDATA, OADDR:
 		n.Left = walkexpr(n.Left, init)
 
-	case OEFACE, OAND, OSUB, OMUL, OADD, OOR, OXOR, OLSH, ORSH:
+	case OEFACE, OAND, OANDNOT, OSUB, OMUL, OADD, OOR, OXOR, OLSH, ORSH:
 		n.Left = walkexpr(n.Left, init)
 		n.Right = walkexpr(n.Right, init)
 
@@ -965,14 +965,6 @@ opswitch:
 		fn := basicnames[param] + "to" + basicnames[result]
 		n = conv(mkcall(fn, types.Types[result], init, conv(n.Left, types.Types[param])), n.Type)
 
-	case OANDNOT:
-		n.Left = walkexpr(n.Left, init)
-		n.Op = OAND
-		n.SetImplicit(true) // for walkCheckPtrArithmetic
-		n.Right = nod(OBITNOT, n.Right, nil)
-		n.Right = typecheck(n.Right, ctxExpr)
-		n.Right = walkexpr(n.Right, init)
-
 	case ODIV, OMOD:
 		n.Left = walkexpr(n.Left, init)
 		n.Right = walkexpr(n.Right, init)
@@ -3609,14 +3601,20 @@ func bounded(n *Node, max int64) bool {
 	}
 
 	switch n.Op {
-	case OAND:
+	case OAND, OANDNOT:
 		v := int64(-1)
-		if smallintconst(n.Left) {
+		switch {
+		case smallintconst(n.Left):
 			v = n.Left.Int64Val()
-		} else if smallintconst(n.Right) {
+		case smallintconst(n.Right):
 			v = n.Right.Int64Val()
+			if n.Op == OANDNOT {
+				v = ^v
+				if !sign {
+					v &= 1<<uint(bits) - 1
+				}
+			}
 		}
-
 		if 0 <= v && v < max {
 			return true
 		}
@@ -4045,12 +4043,8 @@ func walkCheckPtrArithmetic(n *Node, init *Nodes) *Node {
 		case OADD:
 			walk(n.Left)
 			walk(n.Right)
-		case OSUB:
+		case OSUB, OANDNOT:
 			walk(n.Left)
-		case OAND:
-			if n.Implicit() { // was OANDNOT
-				walk(n.Left)
-			}
 		case OCONVNOP:
 			if n.Left.Type.IsUnsafePtr() {
 				n.Left = cheapexpr(n.Left, init)

test/bounds.go

@@ -209,6 +209,11 @@ func main() {
 	use(a1k[i&^0])
 	use(a1k[i&^-2]) // ERROR "index bounds check elided"
 	use(a1k[i&^1])
+	use(a1k[i8&^0])
+	use(a1k[i8&^-128]) // ERROR "index bounds check elided"
+	use(a1k[ui8&^1])   // ERROR "index bounds check elided"
+	use(a1k[ui16&^0xf000])
+	use(a1k[ui16&^0xff00]) // ERROR "index bounds check elided"
 
 	// Right shift cuts the effective number of bits in the index,
 	// but only for unsigned (signed stays negative).