[dev.ssa] cmd/compile: implement non-numeric comparisons

The only slice/interface comparisons that reach
the backend are comparisons to nil.

Funcs, maps, and channels are references types,
so pointer equality is enough.

Change-Id: I60a71da46a36202e9bd62ed370ab7d7f2e2800e7
Reviewed-on: https://go-review.googlesource.com/12715Reviewed-by: Keith Randall <khr@golang.org>

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

@@ -726,6 +726,7 @@ var opToSSA = map[opAndType]ssa.Op{
 	opAndType{ORSH, TINT64}:  ssa.OpRsh64,
 	opAndType{ORSH, TUINT64}: ssa.OpRsh64U,
 
+	opAndType{OEQ, TBOOL}:    ssa.OpEq8,
 	opAndType{OEQ, TINT8}:    ssa.OpEq8,
 	opAndType{OEQ, TUINT8}:   ssa.OpEq8,
 	opAndType{OEQ, TINT16}:   ssa.OpEq16,
@@ -735,7 +736,14 @@ var opToSSA = map[opAndType]ssa.Op{
 	opAndType{OEQ, TINT64}:   ssa.OpEq64,
 	opAndType{OEQ, TUINT64}:  ssa.OpEq64,
 	opAndType{OEQ, TPTR64}:   ssa.OpEq64,
-
+	opAndType{OEQ, TINTER}:   ssa.OpEqFat, // e == nil only
+	opAndType{OEQ, TARRAY}:   ssa.OpEqFat, // slice only; a == nil only
+	opAndType{OEQ, TFUNC}:    ssa.OpEqPtr,
+	opAndType{OEQ, TMAP}:     ssa.OpEqPtr,
+	opAndType{OEQ, TCHAN}:    ssa.OpEqPtr,
+	opAndType{OEQ, TUINTPTR}: ssa.OpEqPtr,
+
+	opAndType{ONE, TBOOL}:    ssa.OpNeq8,
 	opAndType{ONE, TINT8}:    ssa.OpNeq8,
 	opAndType{ONE, TUINT8}:   ssa.OpNeq8,
 	opAndType{ONE, TINT16}:   ssa.OpNeq16,
@@ -745,6 +753,12 @@ var opToSSA = map[opAndType]ssa.Op{
 	opAndType{ONE, TINT64}:   ssa.OpNeq64,
 	opAndType{ONE, TUINT64}:  ssa.OpNeq64,
 	opAndType{ONE, TPTR64}:   ssa.OpNeq64,
+	opAndType{ONE, TINTER}:   ssa.OpNeqFat, // e != nil only
+	opAndType{ONE, TARRAY}:   ssa.OpNeqFat, // slice only; a != nil only
+	opAndType{ONE, TFUNC}:    ssa.OpNeqPtr,
+	opAndType{ONE, TMAP}:     ssa.OpNeqPtr,
+	opAndType{ONE, TCHAN}:    ssa.OpNeqPtr,
+	opAndType{ONE, TUINTPTR}: ssa.OpNeqPtr,
 
 	opAndType{OLT, TINT8}:   ssa.OpLess8,
 	opAndType{OLT, TUINT8}:  ssa.OpLess8U,

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

@@ -100,11 +100,13 @@
 (Eq32 x y) -> (SETEQ (CMPL <TypeFlags> x y))
 (Eq16 x y) -> (SETEQ (CMPW <TypeFlags> x y))
 (Eq8 x y) -> (SETEQ (CMPB <TypeFlags> x y))
+(EqPtr x y) -> (SETEQ (CMPQ <TypeFlags> x y))
 
 (Neq64 x y) -> (SETNE (CMPQ <TypeFlags> x y))
 (Neq32 x y) -> (SETNE (CMPL <TypeFlags> x y))
 (Neq16 x y) -> (SETNE (CMPW <TypeFlags> x y))
 (Neq8 x y) -> (SETNE (CMPB <TypeFlags> x y))
+(NeqPtr x y) -> (SETNE (CMPQ <TypeFlags> x y))
 
 (Load <t> ptr mem) && (is64BitInt(t) || isPtr(t)) -> (MOVQload ptr mem)
 (Load <t> ptr mem) && is32BitInt(t) -> (MOVLload ptr mem)

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

@@ -34,6 +34,15 @@
 (SliceLen (Load ptr mem)) -> (Load (AddPtr <ptr.Type> ptr (Const <config.Uintptr> [config.PtrSize])) mem)
 (SliceCap (Load ptr mem)) -> (Load (AddPtr <ptr.Type> ptr (Const <config.Uintptr> [config.PtrSize*2])) mem)
 
+// slice and interface comparisons
+// the frontend ensures that we can only compare against nil
+// start by putting nil on the right to simplify the other rules
+(EqFat x y) && x.Op == OpConst && y.Op != OpConst -> (EqFat y x)
+(NeqFat x y) && x.Op == OpConst && y.Op != OpConst -> (NeqFat y x)
+// it suffices to check the first word (backing array for slices, dynamic type for interfaces)
+(EqFat (Load ptr mem) y) && y.Op == OpConst -> (EqPtr (Load <config.Uintptr> ptr mem) (Const <config.Uintptr> [0]))
+(NeqFat (Load ptr mem) y) && y.Op == OpConst -> (NeqPtr (Load <config.Uintptr> ptr mem) (Const <config.Uintptr> [0]))
+
 // indexing operations
 // Note: bounds check has already been done
 (ArrayIndex (Load ptr mem) idx) -> (Load (PtrIndex <v.Type.PtrTo()> ptr idx) mem)

src/cmd/compile/internal/ssa/gen/genericOps.go

@@ -67,11 +67,15 @@ var genericOps = []opData{
 	{name: "Eq16"},
 	{name: "Eq32"},
 	{name: "Eq64"},
+	{name: "EqPtr"},
+	{name: "EqFat"}, // slice/interface; arg0 or arg1 is nil; other cases handled by frontend
 
 	{name: "Neq8"}, // arg0 != arg1
 	{name: "Neq16"},
 	{name: "Neq32"},
 	{name: "Neq64"},
+	{name: "NeqPtr"},
+	{name: "NeqFat"}, // slice/interface; arg0 or arg1 is nil; other cases handled by frontend
 
 	{name: "Less8"}, // arg0 < arg1
 	{name: "Less8U"},

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

@@ -183,10 +183,14 @@ const (
 	OpEq16
 	OpEq32
 	OpEq64
+	OpEqPtr
+	OpEqFat
 	OpNeq8
 	OpNeq16
 	OpNeq32
 	OpNeq64
+	OpNeqPtr
+	OpNeqFat
 	OpLess8
 	OpLess8U
 	OpLess16
@@ -1417,6 +1421,14 @@ var opcodeTable = [...]opInfo{
 		name:    "Eq64",
 		generic: true,
 	},
+	{
+		name:    "EqPtr",
+		generic: true,
+	},
+	{
+		name:    "EqFat",
+		generic: true,
+	},
 	{
 		name:    "Neq8",
 		generic: true,
@@ -1433,6 +1445,14 @@ var opcodeTable = [...]opInfo{
 		name:    "Neq64",
 		generic: true,
 	},
+	{
+		name:    "NeqPtr",
+		generic: true,
+	},
+	{
+		name:    "NeqFat",
+		generic: true,
+	},
 	{
 		name:    "Less8",
 		generic: true,

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

@@ -852,6 +852,27 @@ func rewriteValueAMD64(v *Value, config *Config) bool {
 		goto end84a692e769900e3adbfe00718d2169e0
 	end84a692e769900e3adbfe00718d2169e0:
 		;
+	case OpEqPtr:
+		// match: (EqPtr x y)
+		// cond:
+		// result: (SETEQ (CMPQ <TypeFlags> x y))
+		{
+			x := v.Args[0]
+			y := v.Args[1]
+			v.Op = OpAMD64SETEQ
+			v.AuxInt = 0
+			v.Aux = nil
+			v.resetArgs()
+			v0 := v.Block.NewValue0(v.Line, OpAMD64CMPQ, TypeInvalid)
+			v0.Type = TypeFlags
+			v0.AddArg(x)
+			v0.AddArg(y)
+			v.AddArg(v0)
+			return true
+		}
+		goto end6de1d39c9d151e5e503d643bd835356e
+	end6de1d39c9d151e5e503d643bd835356e:
+		;
 	case OpGeq64:
 		// match: (Geq64 x y)
 		// cond:
@@ -2041,6 +2062,27 @@ func rewriteValueAMD64(v *Value, config *Config) bool {
 		goto end4aaff28af59a65b3684f4f1897299932
 	end4aaff28af59a65b3684f4f1897299932:
 		;
+	case OpNeqPtr:
+		// match: (NeqPtr x y)
+		// cond:
+		// result: (SETNE (CMPQ <TypeFlags> x y))
+		{
+			x := v.Args[0]
+			y := v.Args[1]
+			v.Op = OpAMD64SETNE
+			v.AuxInt = 0
+			v.Aux = nil
+			v.resetArgs()
+			v0 := v.Block.NewValue0(v.Line, OpAMD64CMPQ, TypeInvalid)
+			v0.Type = TypeFlags
+			v0.AddArg(x)
+			v0.AddArg(y)
+			v.AddArg(v0)
+			return true
+		}
+		goto end6e180ffd9583cd55361ed3e465158a4c
+	end6e180ffd9583cd55361ed3e465158a4c:
+		;
 	case OpNot:
 		// match: (Not x)
 		// cond:

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

@@ -129,6 +129,58 @@ func rewriteValuegeneric(v *Value, config *Config) bool {
 		goto enda6f250a3c775ae5a239ece8074b46cea
 	enda6f250a3c775ae5a239ece8074b46cea:
 		;
+	case OpEqFat:
+		// match: (EqFat x y)
+		// cond: x.Op == OpConst && y.Op != OpConst
+		// result: (EqFat y x)
+		{
+			x := v.Args[0]
+			y := v.Args[1]
+			if !(x.Op == OpConst && y.Op != OpConst) {
+				goto end4540bddcf0fc8e4b71fac6e9edbb8eec
+			}
+			v.Op = OpEqFat
+			v.AuxInt = 0
+			v.Aux = nil
+			v.resetArgs()
+			v.AddArg(y)
+			v.AddArg(x)
+			return true
+		}
+		goto end4540bddcf0fc8e4b71fac6e9edbb8eec
+	end4540bddcf0fc8e4b71fac6e9edbb8eec:
+		;
+		// match: (EqFat (Load ptr mem) y)
+		// cond: y.Op == OpConst
+		// result: (EqPtr (Load <config.Uintptr> ptr mem) (Const <config.Uintptr> [0]))
+		{
+			if v.Args[0].Op != OpLoad {
+				goto end779b0e24e33d8eff668c368b90387caa
+			}
+			ptr := v.Args[0].Args[0]
+			mem := v.Args[0].Args[1]
+			y := v.Args[1]
+			if !(y.Op == OpConst) {
+				goto end779b0e24e33d8eff668c368b90387caa
+			}
+			v.Op = OpEqPtr
+			v.AuxInt = 0
+			v.Aux = nil
+			v.resetArgs()
+			v0 := v.Block.NewValue0(v.Line, OpLoad, TypeInvalid)
+			v0.Type = config.Uintptr
+			v0.AddArg(ptr)
+			v0.AddArg(mem)
+			v.AddArg(v0)
+			v1 := v.Block.NewValue0(v.Line, OpConst, TypeInvalid)
+			v1.Type = config.Uintptr
+			v1.AuxInt = 0
+			v.AddArg(v1)
+			return true
+		}
+		goto end779b0e24e33d8eff668c368b90387caa
+	end779b0e24e33d8eff668c368b90387caa:
+		;
 	case OpIsInBounds:
 		// match: (IsInBounds (Const [c]) (Const [d]))
 		// cond:
@@ -255,6 +307,58 @@ func rewriteValuegeneric(v *Value, config *Config) bool {
 		goto end10541de7ea2bce703c1e372ac9a271e7
 	end10541de7ea2bce703c1e372ac9a271e7:
 		;
+	case OpNeqFat:
+		// match: (NeqFat x y)
+		// cond: x.Op == OpConst && y.Op != OpConst
+		// result: (NeqFat y x)
+		{
+			x := v.Args[0]
+			y := v.Args[1]
+			if !(x.Op == OpConst && y.Op != OpConst) {
+				goto end5d2a9d3aa52fb6866825f35ac65c7cfd
+			}
+			v.Op = OpNeqFat
+			v.AuxInt = 0
+			v.Aux = nil
+			v.resetArgs()
+			v.AddArg(y)
+			v.AddArg(x)
+			return true
+		}
+		goto end5d2a9d3aa52fb6866825f35ac65c7cfd
+	end5d2a9d3aa52fb6866825f35ac65c7cfd:
+		;
+		// match: (NeqFat (Load ptr mem) y)
+		// cond: y.Op == OpConst
+		// result: (NeqPtr (Load <config.Uintptr> ptr mem) (Const <config.Uintptr> [0]))
+		{
+			if v.Args[0].Op != OpLoad {
+				goto endf2f18052c2d999a7ac883c441c3b7ade
+			}
+			ptr := v.Args[0].Args[0]
+			mem := v.Args[0].Args[1]
+			y := v.Args[1]
+			if !(y.Op == OpConst) {
+				goto endf2f18052c2d999a7ac883c441c3b7ade
+			}
+			v.Op = OpNeqPtr
+			v.AuxInt = 0
+			v.Aux = nil
+			v.resetArgs()
+			v0 := v.Block.NewValue0(v.Line, OpLoad, TypeInvalid)
+			v0.Type = config.Uintptr
+			v0.AddArg(ptr)
+			v0.AddArg(mem)
+			v.AddArg(v0)
+			v1 := v.Block.NewValue0(v.Line, OpConst, TypeInvalid)
+			v1.Type = config.Uintptr
+			v1.AuxInt = 0
+			v.AddArg(v1)
+			return true
+		}
+		goto endf2f18052c2d999a7ac883c441c3b7ade
+	endf2f18052c2d999a7ac883c441c3b7ade:
+		;
 	case OpPtrIndex:
 		// match: (PtrIndex <t> ptr idx)
 		// cond: