cmd/compile: move slice construction to callers of makeslice

Only return a pointer p to the new slices backing array from makeslice.
Makeslice callers then construct sliceheader{p, len, cap} explictly
instead of makeslice returning the slice.

Reduces go binary size by ~0.2%.
Removes 92 (~3.5%) panicindex calls from go binary.

Change-Id: I29b7c3b5fe8b9dcec96e2c43730575071cfe8a94
Reviewed-on: https://go-review.googlesource.com/c/141822
Run-TryBot: Martin Möhrmann <moehrmann@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>

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

@@ -117,8 +117,8 @@ var runtimeDecls = [...]struct {
 	{"selectsetpc", funcTag, 56},
 	{"selectgo", funcTag, 93},
 	{"block", funcTag, 5},
-	{"makeslice", funcTag, 95},
-	{"makeslice64", funcTag, 96},
+	{"makeslice", funcTag, 94},
+	{"makeslice64", funcTag, 95},
 	{"growslice", funcTag, 97},
 	{"memmove", funcTag, 98},
 	{"memclrNoHeapPointers", funcTag, 99},
@@ -249,10 +249,10 @@ func runtimeTypes() []*types.Type {
 	typs[91] = types.NewPtr(typs[11])
 	typs[92] = functype(nil, []*Node{anonfield(typs[3]), anonfield(typs[91]), anonfield(typs[79])}, []*Node{anonfield(typs[11])})
 	typs[93] = functype(nil, []*Node{anonfield(typs[1]), anonfield(typs[1]), anonfield(typs[32])}, []*Node{anonfield(typs[32]), anonfield(typs[11])})
-	typs[94] = types.NewSlice(typs[2])
-	typs[95] = functype(nil, []*Node{anonfield(typs[1]), anonfield(typs[32]), anonfield(typs[32])}, []*Node{anonfield(typs[94])})
-	typs[96] = functype(nil, []*Node{anonfield(typs[1]), anonfield(typs[15]), anonfield(typs[15])}, []*Node{anonfield(typs[94])})
-	typs[97] = functype(nil, []*Node{anonfield(typs[1]), anonfield(typs[94]), anonfield(typs[32])}, []*Node{anonfield(typs[94])})
+	typs[94] = functype(nil, []*Node{anonfield(typs[1]), anonfield(typs[32]), anonfield(typs[32])}, []*Node{anonfield(typs[58])})
+	typs[95] = functype(nil, []*Node{anonfield(typs[1]), anonfield(typs[15]), anonfield(typs[15])}, []*Node{anonfield(typs[58])})
+	typs[96] = types.NewSlice(typs[2])
+	typs[97] = functype(nil, []*Node{anonfield(typs[1]), anonfield(typs[96]), anonfield(typs[32])}, []*Node{anonfield(typs[96])})
 	typs[98] = functype(nil, []*Node{anonfield(typs[3]), anonfield(typs[3]), anonfield(typs[47])}, nil)
 	typs[99] = functype(nil, []*Node{anonfield(typs[58]), anonfield(typs[47])}, nil)
 	typs[100] = functype(nil, []*Node{anonfield(typs[3]), anonfield(typs[3]), anonfield(typs[47])}, []*Node{anonfield(typs[11])})

src/cmd/compile/internal/gc/builtin/runtime.go

@@ -153,8 +153,8 @@ func selectsetpc(cas *byte)
 func selectgo(cas0 *byte, order0 *byte, ncases int) (int, bool)
 func block()
 
-func makeslice(typ *byte, len int, cap int) (ary []any)
-func makeslice64(typ *byte, len int64, cap int64) (ary []any)
+func makeslice(typ *byte, len int, cap int) unsafe.Pointer
+func makeslice64(typ *byte, len int64, cap int64) unsafe.Pointer
 func growslice(typ *byte, old []any, cap int) (ary []any)
 func memmove(to *any, frm *any, length uintptr)
 func memclrNoHeapPointers(ptr unsafe.Pointer, n uintptr)

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

@@ -4,9 +4,9 @@ package gc
 
 import "strconv"
 
-const _Op_name = "XXXNAMENONAMETYPEPACKLITERALADDSUBORXORADDSTRADDRANDANDAPPENDARRAYBYTESTRARRAYBYTESTRTMPARRAYRUNESTRSTRARRAYBYTESTRARRAYBYTETMPSTRARRAYRUNEASAS2AS2FUNCAS2RECVAS2MAPRAS2DOTTYPEASOPCALLCALLFUNCCALLMETHCALLINTERCALLPARTCAPCLOSECLOSURECOMPLITMAPLITSTRUCTLITARRAYLITSLICELITPTRLITCONVCONVIFACECONVNOPCOPYDCLDCLFUNCDCLFIELDDCLCONSTDCLTYPEDELETEDOTDOTPTRDOTMETHDOTINTERXDOTDOTTYPEDOTTYPE2EQNELTLEGEGTINDINDEXINDEXMAPKEYSTRUCTKEYLENMAKEMAKECHANMAKEMAPMAKESLICEMULDIVMODLSHRSHANDANDNOTNEWNOTCOMPLUSMINUSORORPANICPRINTPRINTNPARENSENDSLICESLICEARRSLICESTRSLICE3SLICE3ARRRECOVERRECVRUNESTRSELRECVSELRECV2IOTAREALIMAGCOMPLEXALIGNOFOFFSETOFSIZEOFBLOCKBREAKCASEXCASECONTINUEDEFEREMPTYFALLFORFORUNTILGOTOIFLABELPROCRANGERETURNSELECTSWITCHTYPESWTCHANTMAPTSTRUCTTINTERTFUNCTARRAYDDDDDDARGINLCALLEFACEITABIDATASPTRCLOSUREVARCFUNCCHECKNILVARDEFVARKILLVARLIVEINDREGSPRETJMPGETGEND"
+const _Op_name = "XXXNAMENONAMETYPEPACKLITERALADDSUBORXORADDSTRADDRANDANDAPPENDARRAYBYTESTRARRAYBYTESTRTMPARRAYRUNESTRSTRARRAYBYTESTRARRAYBYTETMPSTRARRAYRUNEASAS2AS2FUNCAS2RECVAS2MAPRAS2DOTTYPEASOPCALLCALLFUNCCALLMETHCALLINTERCALLPARTCAPCLOSECLOSURECOMPLITMAPLITSTRUCTLITARRAYLITSLICELITPTRLITCONVCONVIFACECONVNOPCOPYDCLDCLFUNCDCLFIELDDCLCONSTDCLTYPEDELETEDOTDOTPTRDOTMETHDOTINTERXDOTDOTTYPEDOTTYPE2EQNELTLEGEGTINDINDEXINDEXMAPKEYSTRUCTKEYLENMAKEMAKECHANMAKEMAPMAKESLICEMULDIVMODLSHRSHANDANDNOTNEWNOTCOMPLUSMINUSORORPANICPRINTPRINTNPARENSENDSLICESLICEARRSLICESTRSLICEHEADERSLICE3SLICE3ARRRECOVERRECVRUNESTRSELRECVSELRECV2IOTAREALIMAGCOMPLEXALIGNOFOFFSETOFSIZEOFBLOCKBREAKCASEXCASECONTINUEDEFEREMPTYFALLFORFORUNTILGOTOIFLABELPROCRANGERETURNSELECTSWITCHTYPESWTCHANTMAPTSTRUCTTINTERTFUNCTARRAYDDDDDDARGINLCALLEFACEITABIDATASPTRCLOSUREVARCFUNCCHECKNILVARDEFVARKILLVARLIVEINDREGSPRETJMPGETGEND"
 
-var _Op_index = [...]uint16{0, 3, 7, 13, 17, 21, 28, 31, 34, 36, 39, 45, 49, 55, 61, 73, 88, 100, 112, 127, 139, 141, 144, 151, 158, 165, 175, 179, 183, 191, 199, 208, 216, 219, 224, 231, 238, 244, 253, 261, 269, 275, 279, 288, 295, 299, 302, 309, 317, 325, 332, 338, 341, 347, 354, 362, 366, 373, 381, 383, 385, 387, 389, 391, 393, 396, 401, 409, 412, 421, 424, 428, 436, 443, 452, 455, 458, 461, 464, 467, 470, 476, 479, 482, 485, 489, 494, 498, 503, 508, 514, 519, 523, 528, 536, 544, 550, 559, 566, 570, 577, 584, 592, 596, 600, 604, 611, 618, 626, 632, 637, 642, 646, 651, 659, 664, 669, 673, 676, 684, 688, 690, 695, 699, 704, 710, 716, 722, 728, 733, 737, 744, 750, 755, 761, 764, 770, 777, 782, 786, 791, 795, 805, 810, 818, 824, 831, 838, 846, 852, 856, 859}
+var _Op_index = [...]uint16{0, 3, 7, 13, 17, 21, 28, 31, 34, 36, 39, 45, 49, 55, 61, 73, 88, 100, 112, 127, 139, 141, 144, 151, 158, 165, 175, 179, 183, 191, 199, 208, 216, 219, 224, 231, 238, 244, 253, 261, 269, 275, 279, 288, 295, 299, 302, 309, 317, 325, 332, 338, 341, 347, 354, 362, 366, 373, 381, 383, 385, 387, 389, 391, 393, 396, 401, 409, 412, 421, 424, 428, 436, 443, 452, 455, 458, 461, 464, 467, 470, 476, 479, 482, 485, 489, 494, 498, 503, 508, 514, 519, 523, 528, 536, 544, 555, 561, 570, 577, 581, 588, 595, 603, 607, 611, 615, 622, 629, 637, 643, 648, 653, 657, 662, 670, 675, 680, 684, 687, 695, 699, 701, 706, 710, 715, 721, 727, 733, 739, 744, 748, 755, 761, 766, 772, 775, 781, 788, 793, 797, 802, 806, 816, 821, 829, 835, 842, 849, 857, 863, 867, 870}
 
 func (i Op) String() string {
 	if i >= Op(len(_Op_index)-1) {

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

@@ -2321,6 +2321,12 @@ func (s *state) expr(n *Node) *ssa.Value {
 		data := s.expr(n.Right)
 		return s.newValue2(ssa.OpIMake, n.Type, tab, data)
 
+	case OSLICEHEADER:
+		p := s.expr(n.Left)
+		l := s.expr(n.List.First())
+		c := s.expr(n.List.Second())
+		return s.newValue3(ssa.OpSliceMake, n.Type, p, l, c)
+
 	case OSLICE, OSLICEARR, OSLICE3, OSLICE3ARR:
 		v := s.expr(n.Left)
 		var i, j, k *ssa.Value

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

@@ -683,6 +683,7 @@ const (
 	OSLICESTR    // Left[List[0] : List[1]] (Left is string)
 	OSLICE3      // Left[List[0] : List[1] : List[2]] (Left is untypedchecked or slice)
 	OSLICE3ARR   // Left[List[0] : List[1] : List[2]] (Left is array)
+	OSLICEHEADER // sliceheader{Left, List[0], List[1]} (Left is unsafe.Pointer, List[0] is length, List[1] is capacity)
 	ORECOVER     // recover()
 	ORECV        // <-Left
 	ORUNESTR     // Type(Left) (Type is string, Left is rune)

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

@@ -1086,6 +1086,47 @@ func typecheck1(n *Node, top int) *Node {
 		n.Right = assignconv(r, t.Elem(), "send")
 		n.Type = nil
 
+	case OSLICEHEADER:
+		// Errors here are Fatalf instead of yyerror because only the compiler
+		// can construct an OSLICEHEADER node.
+		// Components used in OSLICEHEADER that are supplied by parsed source code
+		// have already been typechecked in e.g. OMAKESLICE earlier.
+		ok |= Erv
+
+		t := n.Type
+		if !t.IsSlice() {
+			Fatalf("invalid type %v for OSLICEHEADER", n.Type)
+		}
+
+		if !n.Left.Type.IsUnsafePtr() {
+			Fatalf("need unsafe.Pointer for OSLICEHEADER")
+		}
+
+		if x := n.List.Len(); x != 2 {
+			Fatalf("expected 2 params (len, cap) for OSLICEHEADER, got %d", x)
+		}
+
+		n.Left = typecheck(n.Left, Erv)
+		l := typecheck(n.List.First(), Erv)
+		c := typecheck(n.List.Second(), Erv)
+		l = defaultlit(l, types.Types[TINT])
+		c = defaultlit(c, types.Types[TINT])
+
+		if Isconst(l, CTINT) && l.Int64() < 0 {
+			Fatalf("len for OSLICEHEADER must be non-negative")
+		}
+
+		if Isconst(c, CTINT) && c.Int64() < 0 {
+			Fatalf("cap for OSLICEHEADER must be non-negative")
+		}
+
+		if Isconst(l, CTINT) && Isconst(c, CTINT) && l.Val().U.(*Mpint).Cmp(c.Val().U.(*Mpint)) > 0 {
+			Fatalf("len larger than cap for OSLICEHEADER")
+		}
+
+		n.List.SetFirst(l)
+		n.List.SetSecond(c)
+
 	case OSLICE, OSLICE3:
 		ok |= Erv
 		n.Left = typecheck(n.Left, Erv)

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

@@ -1118,6 +1118,11 @@ opswitch:
 	case ORECV:
 		Fatalf("walkexpr ORECV") // should see inside OAS only
 
+	case OSLICEHEADER:
+		n.Left = walkexpr(n.Left, init)
+		n.List.SetFirst(walkexpr(n.List.First(), init))
+		n.List.SetSecond(walkexpr(n.List.Second(), init))
+
 	case OSLICE, OSLICEARR, OSLICESTR, OSLICE3, OSLICE3ARR:
 		n.Left = walkexpr(n.Left, init)
 		low, high, max := n.SliceBounds()
@@ -1339,8 +1344,13 @@ opswitch:
 			}
 
 			fn := syslook(fnname)
-			fn = substArgTypes(fn, t.Elem()) // any-1
-			n = mkcall1(fn, t, init, typename(t.Elem()), conv(len, argtype), conv(cap, argtype))
+			n.Left = mkcall1(fn, types.Types[TUNSAFEPTR], init, typename(t.Elem()), conv(len, argtype), conv(cap, argtype))
+			n.Left.SetNonNil(true)
+			n.List.Set2(conv(len, types.Types[TINT]), conv(cap, types.Types[TINT]))
+			n.Op = OSLICEHEADER
+			n.Type = t
+			n = typecheck(n, Erv)
+			n = walkexpr(n, init)
 		}
 
 	case ORUNESTR:

src/runtime/runtime-gdb_test.go

@@ -266,8 +266,11 @@ func testGdbPython(t *testing.T, cgo bool) {
 	infoLocalsRe1 := regexp.MustCompile(`slicevar *= *\[\]string *= *{"def"}`)
 	// Format output from gdb v8.2
 	infoLocalsRe2 := regexp.MustCompile(`^slicevar = .*\nmapvar = .*\nstrvar = 0x[0-9a-f]+ "abc"`)
+	// Format output from gdb v7.7
+	infoLocalsRe3 := regexp.MustCompile(`^mapvar = .*\nstrvar = "abc"\nslicevar *= *\[\]string`)
 	if bl := blocks["info locals"]; !infoLocalsRe1.MatchString(bl) &&
-		!infoLocalsRe2.MatchString(bl) {
+		!infoLocalsRe2.MatchString(bl) &&
+		!infoLocalsRe3.MatchString(bl) {
 		t.Fatalf("info locals failed: %s", bl)
 	}
 

src/runtime/slice.go

@@ -31,7 +31,7 @@ func panicmakeslicecap() {
 	panic(errorString("makeslice: cap out of range"))
 }
 
-func makeslice(et *_type, len, cap int) slice {
+func makeslice(et *_type, len, cap int) unsafe.Pointer {
 	mem, overflow := math.MulUintptr(et.size, uintptr(cap))
 	if overflow || mem > maxAlloc || len < 0 || len > cap {
 		// NOTE: Produce a 'len out of range' error instead of a
@@ -45,12 +45,11 @@ func makeslice(et *_type, len, cap int) slice {
 		}
 		panicmakeslicecap()
 	}
-	p := mallocgc(mem, et, true)
 
-	return slice{p, len, cap}
+	return mallocgc(mem, et, true)
 }
 
-func makeslice64(et *_type, len64, cap64 int64) slice {
+func makeslice64(et *_type, len64, cap64 int64) unsafe.Pointer {
 	len := int(len64)
 	if int64(len) != len64 {
 		panicmakeslicelen()