[dev.ssa] cmd/compile/internal/ssa: implement OHMUL

Adds support for high multiply which is used by the frontend when
rewriting const division.  The frontend currently only does this for 8,
16, and 32 bit integer arithmetic.

Change-Id: I9b6c6018f3be827a50ee6c185454ebc79b3094c8
Reviewed-on: https://go-review.googlesource.com/13696Reviewed-by: Keith Randall <khr@golang.org>

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

@@ -779,6 +779,13 @@ var opToSSA = map[opAndType]ssa.Op{
 	opAndType{ODIV, TFLOAT32}: ssa.OpDiv32F,
 	opAndType{ODIV, TFLOAT64}: ssa.OpDiv64F,
 
+	opAndType{OHMUL, TINT8}:   ssa.OpHmul8,
+	opAndType{OHMUL, TUINT8}:  ssa.OpHmul8u,
+	opAndType{OHMUL, TINT16}:  ssa.OpHmul16,
+	opAndType{OHMUL, TUINT16}: ssa.OpHmul16u,
+	opAndType{OHMUL, TINT32}:  ssa.OpHmul32,
+	opAndType{OHMUL, TUINT32}: ssa.OpHmul32u,
+
 	opAndType{ODIV, TINT8}:   ssa.OpDiv8,
 	opAndType{ODIV, TUINT8}:  ssa.OpDiv8u,
 	opAndType{ODIV, TINT16}:  ssa.OpDiv16,
@@ -1201,7 +1208,7 @@ 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.Left.Type), Types[TBOOL], a, b)
-	case OADD, OAND, OMUL, OOR, OSUB, ODIV, OXOR:
+	case OADD, OAND, OMUL, OOR, OSUB, ODIV, OXOR, OHMUL:
 		a := s.expr(n.Left)
 		b := s.expr(n.Right)
 		return s.newValue2(s.ssaOp(n.Op, n.Type), a.Type, a, b)
@@ -2099,6 +2106,27 @@ func genValue(v *ssa.Value) {
 			j2.To.Val = Pc
 		}
 
+	case ssa.OpAMD64HMULL, ssa.OpAMD64HMULW, ssa.OpAMD64HMULB,
+		ssa.OpAMD64HMULLU, ssa.OpAMD64HMULWU, ssa.OpAMD64HMULBU:
+		// the frontend rewrites constant division by 8/16/32 bit integers into
+		// HMUL by a constant
+
+		// Arg[0] is already in AX as it's the only register we allow
+		// and DX is the only output we care about (the high bits)
+		p := Prog(v.Op.Asm())
+		p.From.Type = obj.TYPE_REG
+		p.From.Reg = regnum(v.Args[1])
+
+		// IMULB puts the high portion in AH instead of DL,
+		// so move it to DL for consistency
+		if v.Type.Size() == 1 {
+			m := Prog(x86.AMOVB)
+			m.From.Type = obj.TYPE_REG
+			m.From.Reg = x86.REG_AH
+			m.To.Type = obj.TYPE_REG
+			m.To.Reg = x86.REG_DX
+		}
+
 	case ssa.OpAMD64SHLQ, ssa.OpAMD64SHLL, ssa.OpAMD64SHLW, ssa.OpAMD64SHLB,
 		ssa.OpAMD64SHRQ, ssa.OpAMD64SHRL, ssa.OpAMD64SHRW, ssa.OpAMD64SHRB,
 		ssa.OpAMD64SARQ, ssa.OpAMD64SARL, ssa.OpAMD64SARW, ssa.OpAMD64SARB:

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

@@ -51,3 +51,6 @@ func TestFP(t *testing.T) { runTest(t, "fp_ssa.go") }
 
 // TestArithmeticBoundary tests boundary results for arithmetic operations.
 func TestArithmeticBoundary(t *testing.T) { runTest(t, "arithBoundary_ssa.go") }
+
+// TestArithmeticConst tests results for arithmetic operations against constants.
+func TestArithmeticConst(t *testing.T) { runTest(t, "arithConst_ssa.go") }

src/cmd/compile/internal/gc/testdata/arith_ssa.go

@@ -8,7 +8,7 @@
 
 package main
 
-// test64BitConstMulti tests that rewrite rules don't fold 64 bit constants
+// test64BitConstMult tests that rewrite rules don't fold 64 bit constants
 // into multiply instructions.
 func test64BitConstMult() {
 	want := int64(103079215109)

src/cmd/compile/internal/ssa/TODO

@@ -5,7 +5,7 @@ Coverage
 --------
 - Floating point numbers
 - Complex numbers
-- Integer division (HMUL & MOD)
+- Integer division (MOD)
 - Fat objects (strings/slices/interfaces) vs. Phi
 - Defer?
 - Closure args
@@ -50,6 +50,7 @@ Optimizations (better compiler)
 - Constant cache
 - Reuseable slices (e.g. []int of size NumValues()) cached in Func
 - Handle signed division overflow and sign extension earlier
+- Implement 64 bit const division with high multiply, maybe in the frontend?
 
 Regalloc
 --------

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

@@ -45,6 +45,13 @@
 (Div8 x y) ->  (DIVW (SignExt8to16 <config.Frontend().TypeInt16()> x) (SignExt8to16 <config.Frontend().TypeInt16()> y))
 (Div8u x y) ->  (DIVWU (ZeroExt8to16 <config.Frontend().TypeUInt16()> x) (ZeroExt8to16 <config.Frontend().TypeUInt16()> y))
 
+(Hmul32 x y) -> (HMULL x y)
+(Hmul32u x y) -> (HMULLU x y)
+(Hmul16 x y) -> (HMULW x y)
+(Hmul16u x y) -> (HMULWU x y)
+(Hmul8 x y) ->  (HMULB x y)
+(Hmul8u x y) ->  (HMULBU x y)
+
 (And64 x y) -> (ANDQ x y)
 (And32 x y) -> (ANDL x y)
 (And16 x y) -> (ANDW x y)

src/cmd/compile/internal/ssa/gen/AMD64Ops.go

@@ -101,6 +101,8 @@ func init() {
 		gp21shift = regInfo{inputs: []regMask{gpsp, cx}, outputs: []regMask{gp &^ cx}, clobbers: flags}
 		gp11div   = regInfo{inputs: []regMask{ax, gpsp &^ dx}, outputs: []regMask{ax},
 			clobbers: dx | flags}
+		gp11hmul = regInfo{inputs: []regMask{ax, gpsp}, outputs: []regMask{dx},
+			clobbers: ax | flags}
 
 		gp2flags = regInfo{inputs: []regMask{gpsp, gpsp}, outputs: flagsonly}
 		gp1flags = regInfo{inputs: []regMask{gpsp}, outputs: flagsonly}
@@ -184,10 +186,16 @@ func init() {
 		{name: "MULWconst", reg: gp11, asm: "IMULW"}, // arg0 * auxint
 		{name: "MULBconst", reg: gp11, asm: "IMULW"}, // arg0 * auxint
 
+		{name: "HMULL", reg: gp11hmul, asm: "IMULL"}, // (arg0 * arg1) >> width
+		{name: "HMULW", reg: gp11hmul, asm: "IMULW"}, // (arg0 * arg1) >> width
+		{name: "HMULB", reg: gp11hmul, asm: "IMULB"}, // (arg0 * arg1) >> width
+		{name: "HMULLU", reg: gp11hmul, asm: "MULL"}, // (arg0 * arg1) >> width
+		{name: "HMULWU", reg: gp11hmul, asm: "MULW"}, // (arg0 * arg1) >> width
+		{name: "HMULBU", reg: gp11hmul, asm: "MULB"}, // (arg0 * arg1) >> width
+
 		{name: "DIVQ", reg: gp11div, asm: "IDIVQ"}, // arg0 / arg1
 		{name: "DIVL", reg: gp11div, asm: "IDIVL"}, // arg0 / arg1
 		{name: "DIVW", reg: gp11div, asm: "IDIVW"}, // arg0 / arg1
-
 		{name: "DIVQU", reg: gp11div, asm: "DIVQ"}, // arg0 / arg1
 		{name: "DIVLU", reg: gp11div, asm: "DIVL"}, // arg0 / arg1
 		{name: "DIVWU", reg: gp11div, asm: "DIVW"}, // arg0 / arg1

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

@@ -37,6 +37,14 @@ var genericOps = []opData{
 	{name: "Div64F"},
 	// TODO: Div8, Div16, Div32, Div64 and unsigned
 
+	{name: "Hmul8"}, // (arg0 * arg1) >> width
+	{name: "Hmul8u"},
+	{name: "Hmul16"},
+	{name: "Hmul16u"},
+	{name: "Hmul32"},
+	{name: "Hmul32u"},
+	// frontend currently doesn't generate a 64 bit hmul
+
 	{name: "Div8"}, // arg0 / arg1
 	{name: "Div8u"},
 	{name: "Div16"},

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

@@ -93,6 +93,12 @@ const (
 	OpAMD64MULLconst
 	OpAMD64MULWconst
 	OpAMD64MULBconst
+	OpAMD64HMULL
+	OpAMD64HMULW
+	OpAMD64HMULB
+	OpAMD64HMULLU
+	OpAMD64HMULWU
+	OpAMD64HMULBU
 	OpAMD64DIVQ
 	OpAMD64DIVL
 	OpAMD64DIVW
@@ -245,6 +251,12 @@ const (
 	OpMul64F
 	OpDiv32F
 	OpDiv64F
+	OpHmul8
+	OpHmul8u
+	OpHmul16
+	OpHmul16u
+	OpHmul32
+	OpHmul32u
 	OpDiv8
 	OpDiv8u
 	OpDiv16
@@ -977,6 +989,90 @@ var opcodeTable = [...]opInfo{
 			},
 		},
 	},
+	{
+		name: "HMULL",
+		asm:  x86.AIMULL,
+		reg: regInfo{
+			inputs: []inputInfo{
+				{0, 1},     // .AX
+				{1, 65535}, // .AX .CX .DX .BX .SP .BP .SI .DI .R8 .R9 .R10 .R11 .R12 .R13 .R14 .R15
+			},
+			clobbers: 8589934593, // .AX .FLAGS
+			outputs: []regMask{
+				4, // .DX
+			},
+		},
+	},
+	{
+		name: "HMULW",
+		asm:  x86.AIMULW,
+		reg: regInfo{
+			inputs: []inputInfo{
+				{0, 1},     // .AX
+				{1, 65535}, // .AX .CX .DX .BX .SP .BP .SI .DI .R8 .R9 .R10 .R11 .R12 .R13 .R14 .R15
+			},
+			clobbers: 8589934593, // .AX .FLAGS
+			outputs: []regMask{
+				4, // .DX
+			},
+		},
+	},
+	{
+		name: "HMULB",
+		asm:  x86.AIMULB,
+		reg: regInfo{
+			inputs: []inputInfo{
+				{0, 1},     // .AX
+				{1, 65535}, // .AX .CX .DX .BX .SP .BP .SI .DI .R8 .R9 .R10 .R11 .R12 .R13 .R14 .R15
+			},
+			clobbers: 8589934593, // .AX .FLAGS
+			outputs: []regMask{
+				4, // .DX
+			},
+		},
+	},
+	{
+		name: "HMULLU",
+		asm:  x86.AMULL,
+		reg: regInfo{
+			inputs: []inputInfo{
+				{0, 1},     // .AX
+				{1, 65535}, // .AX .CX .DX .BX .SP .BP .SI .DI .R8 .R9 .R10 .R11 .R12 .R13 .R14 .R15
+			},
+			clobbers: 8589934593, // .AX .FLAGS
+			outputs: []regMask{
+				4, // .DX
+			},
+		},
+	},
+	{
+		name: "HMULWU",
+		asm:  x86.AMULW,
+		reg: regInfo{
+			inputs: []inputInfo{
+				{0, 1},     // .AX
+				{1, 65535}, // .AX .CX .DX .BX .SP .BP .SI .DI .R8 .R9 .R10 .R11 .R12 .R13 .R14 .R15
+			},
+			clobbers: 8589934593, // .AX .FLAGS
+			outputs: []regMask{
+				4, // .DX
+			},
+		},
+	},
+	{
+		name: "HMULBU",
+		asm:  x86.AMULB,
+		reg: regInfo{
+			inputs: []inputInfo{
+				{0, 1},     // .AX
+				{1, 65535}, // .AX .CX .DX .BX .SP .BP .SI .DI .R8 .R9 .R10 .R11 .R12 .R13 .R14 .R15
+			},
+			clobbers: 8589934593, // .AX .FLAGS
+			outputs: []regMask{
+				4, // .DX
+			},
+		},
+	},
 	{
 		name: "DIVQ",
 		asm:  x86.AIDIVQ,
@@ -2690,6 +2786,30 @@ var opcodeTable = [...]opInfo{
 		name:    "Div64F",
 		generic: true,
 	},
+	{
+		name:    "Hmul8",
+		generic: true,
+	},
+	{
+		name:    "Hmul8u",
+		generic: true,
+	},
+	{
+		name:    "Hmul16",
+		generic: true,
+	},
+	{
+		name:    "Hmul16u",
+		generic: true,
+	},
+	{
+		name:    "Hmul32",
+		generic: true,
+	},
+	{
+		name:    "Hmul32u",
+		generic: true,
+	},
 	{
 		name:    "Div8",
 		generic: true,

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

@@ -2335,6 +2335,114 @@ func rewriteValueAMD64(v *Value, config *Config) bool {
 		goto end22eaafbcfe70447f79d9b3e6cc395bbd
 	end22eaafbcfe70447f79d9b3e6cc395bbd:
 		;
+	case OpHmul16:
+		// match: (Hmul16 x y)
+		// cond:
+		// result: (HMULW x y)
+		{
+			x := v.Args[0]
+			y := v.Args[1]
+			v.Op = OpAMD64HMULW
+			v.AuxInt = 0
+			v.Aux = nil
+			v.resetArgs()
+			v.AddArg(x)
+			v.AddArg(y)
+			return true
+		}
+		goto end1b9ff394bb3b06fc109637656b6875f5
+	end1b9ff394bb3b06fc109637656b6875f5:
+		;
+	case OpHmul16u:
+		// match: (Hmul16u x y)
+		// cond:
+		// result: (HMULWU x y)
+		{
+			x := v.Args[0]
+			y := v.Args[1]
+			v.Op = OpAMD64HMULWU
+			v.AuxInt = 0
+			v.Aux = nil
+			v.resetArgs()
+			v.AddArg(x)
+			v.AddArg(y)
+			return true
+		}
+		goto endee9089e794a43f2ce1619a6ef61670f4
+	endee9089e794a43f2ce1619a6ef61670f4:
+		;
+	case OpHmul32:
+		// match: (Hmul32 x y)
+		// cond:
+		// result: (HMULL x y)
+		{
+			x := v.Args[0]
+			y := v.Args[1]
+			v.Op = OpAMD64HMULL
+			v.AuxInt = 0
+			v.Aux = nil
+			v.resetArgs()
+			v.AddArg(x)
+			v.AddArg(y)
+			return true
+		}
+		goto end7c83c91ef2634f0b1da4f49350b437b1
+	end7c83c91ef2634f0b1da4f49350b437b1:
+		;
+	case OpHmul32u:
+		// match: (Hmul32u x y)
+		// cond:
+		// result: (HMULLU x y)
+		{
+			x := v.Args[0]
+			y := v.Args[1]
+			v.Op = OpAMD64HMULLU
+			v.AuxInt = 0
+			v.Aux = nil
+			v.resetArgs()
+			v.AddArg(x)
+			v.AddArg(y)
+			return true
+		}
+		goto end3c4f36611dc8815aa2a63d4ec0eaa06d
+	end3c4f36611dc8815aa2a63d4ec0eaa06d:
+		;
+	case OpHmul8:
+		// match: (Hmul8 x y)
+		// cond:
+		// result: (HMULB x y)
+		{
+			x := v.Args[0]
+			y := v.Args[1]
+			v.Op = OpAMD64HMULB
+			v.AuxInt = 0
+			v.Aux = nil
+			v.resetArgs()
+			v.AddArg(x)
+			v.AddArg(y)
+			return true
+		}
+		goto end51b2cc9f1ed15314e68fc81024f281a7
+	end51b2cc9f1ed15314e68fc81024f281a7:
+		;
+	case OpHmul8u:
+		// match: (Hmul8u x y)
+		// cond:
+		// result: (HMULBU x y)
+		{
+			x := v.Args[0]
+			y := v.Args[1]
+			v.Op = OpAMD64HMULBU
+			v.AuxInt = 0
+			v.Aux = nil
+			v.resetArgs()
+			v.AddArg(x)
+			v.AddArg(y)
+			return true
+		}
+		goto ende68d7b3a3c774cedc3522af9d635c39d
+	ende68d7b3a3c774cedc3522af9d635c39d:
+		;
 	case OpITab:
 		// match: (ITab (Load ptr mem))
 		// cond: