cmd/compile: add clear(x) builtin

To clear map, and zero content of slice. Updates #56351 Change-Id: I5f81dfbc465500f5acadaf2c6beb9b5f0d2c4045 Reviewed-on: https://go-review.googlesource.com/c/go/+/453395 Reviewed-by: Cherry Mui <cherryyz@google.com> Reviewed-by: Keith Randall <khr@golang.org> TryBot-Result: Gopher Robot <gobot@golang.org> Reviewed-by: Keith Randall <khr@google.com> Run-TryBot: Cuong Manh Le <cuong.manhle.vn@gmail.com> Auto-Submit: Cuong Manh Le <cuong.manhle.vn@gmail.com>
2025-05-05 07:33:00 +00:00 · 2022-11-25 16:11:45 +07:00 · 2022-11-25 16:11:45 +07:00 · b89a840d65
commit b89a840d65
parent bb4ea80bef
17 changed files with 256 additions and 142 deletions
--- a/src/cmd/compile/internal/escape/call.go
+++ b/src/cmd/compile/internal/escape/call.go
@ -179,7 +179,7 @@ func (e *escape) callCommon(ks []hole, call ir.Node, init *ir.Nodes, wrapper *ir
 			argument(e.discardHole(), &call.Args[i])
 		}

-	case ir.OLEN, ir.OCAP, ir.OREAL, ir.OIMAG, ir.OCLOSE:
+	case ir.OLEN, ir.OCAP, ir.OREAL, ir.OIMAG, ir.OCLOSE, ir.OCLEAR:
 		call := call.(*ir.UnaryExpr)
 		argument(e.discardHole(), &call.X)

--- a/src/cmd/compile/internal/escape/stmt.go
+++ b/src/cmd/compile/internal/escape/stmt.go
@ -180,7 +180,7 @@ func (e *escape) stmt(n ir.Node) {
 			dsts[i] = res.Nname.(*ir.Name)
 		}
 		e.assignList(dsts, n.Results, "return", n)
-	case ir.OCALLFUNC, ir.OCALLMETH, ir.OCALLINTER, ir.OINLCALL, ir.OCLOSE, ir.OCOPY, ir.ODELETE, ir.OPANIC, ir.OPRINT, ir.OPRINTN, ir.ORECOVER:
+	case ir.OCALLFUNC, ir.OCALLMETH, ir.OCALLINTER, ir.OINLCALL, ir.OCLEAR, ir.OCLOSE, ir.OCOPY, ir.ODELETE, ir.OPANIC, ir.OPRINT, ir.OPRINTN, ir.ORECOVER:
 		e.call(nil, n)
 	case ir.OGO, ir.ODEFER:
 		n := n.(*ir.GoDeferStmt)
--- a/src/cmd/compile/internal/ir/expr.go
+++ b/src/cmd/compile/internal/ir/expr.go
@ -747,7 +747,7 @@ func (n *UnaryExpr) SetOp(op Op) {
 	default:
 		panic(n.no("SetOp " + op.String()))
 	case OBITNOT, ONEG, ONOT, OPLUS, ORECV,
-		OALIGNOF, OCAP, OCLOSE, OIMAG, OLEN, ONEW,
+		OALIGNOF, OCAP, OCLEAR, OCLOSE, OIMAG, OLEN, ONEW,
 		OOFFSETOF, OPANIC, OREAL, OSIZEOF,
 		OCHECKNIL, OCFUNC, OIDATA, OITAB, OSPTR,
 		OUNSAFESTRINGDATA, OUNSAFESLICEDATA:
--- a/src/cmd/compile/internal/ir/fmt.go
+++ b/src/cmd/compile/internal/ir/fmt.go
@ -39,6 +39,7 @@ var OpNames = []string{
 	OCALL:             "function call", // not actual syntax
 	OCAP:              "cap",
 	OCASE:             "case",
+	OCLEAR:            "clear",
 	OCLOSE:            "close",
 	OCOMPLEX:          "complex",
 	OBITNOT:           "^",
@ -182,6 +183,7 @@ var OpPrec = []int{
 	OCALLMETH:         8,
 	OCALL:             8,
 	OCAP:              8,
+	OCLEAR:            8,
 	OCLOSE:            8,
 	OCOMPLIT:          8,
 	OCONVIFACE:        8,
@ -767,6 +769,7 @@ func exprFmt(n Node, s fmt.State, prec int) {
 	case OREAL,
 		OIMAG,
 		OCAP,
+		OCLEAR,
 		OCLOSE,
 		OLEN,
 		ONEW,
--- a/src/cmd/compile/internal/ir/node.go
+++ b/src/cmd/compile/internal/ir/node.go
@ -159,6 +159,7 @@ const (
 	OCALLMETH  // X(Args) (direct method call x.Method(args))
 	OCALLINTER // X(Args) (interface method call x.Method(args))
 	OCAP       // cap(X)
+	OCLEAR     // clear(X)
 	OCLOSE     // close(X)
 	OCLOSURE   // func Type { Func.Closure.Body } (func literal)
 	OCOMPLIT   // Type{List} (composite literal, not yet lowered to specific form)
--- a/src/cmd/compile/internal/ir/op_string.go
+++ b/src/cmd/compile/internal/ir/op_string.go
@ -42,132 +42,133 @@ func _() {
 	_ = x[OCALLMETH-31]
 	_ = x[OCALLINTER-32]
 	_ = x[OCAP-33]
-	_ = x[OCLOSE-34]
-	_ = x[OCLOSURE-35]
-	_ = x[OCOMPLIT-36]
-	_ = x[OMAPLIT-37]
-	_ = x[OSTRUCTLIT-38]
-	_ = x[OARRAYLIT-39]
-	_ = x[OSLICELIT-40]
-	_ = x[OPTRLIT-41]
-	_ = x[OCONV-42]
-	_ = x[OCONVIFACE-43]
-	_ = x[OCONVIDATA-44]
-	_ = x[OCONVNOP-45]
-	_ = x[OCOPY-46]
-	_ = x[ODCL-47]
-	_ = x[ODCLFUNC-48]
-	_ = x[ODCLCONST-49]
-	_ = x[ODCLTYPE-50]
-	_ = x[ODELETE-51]
-	_ = x[ODOT-52]
-	_ = x[ODOTPTR-53]
-	_ = x[ODOTMETH-54]
-	_ = x[ODOTINTER-55]
-	_ = x[OXDOT-56]
-	_ = x[ODOTTYPE-57]
-	_ = x[ODOTTYPE2-58]
-	_ = x[OEQ-59]
-	_ = x[ONE-60]
-	_ = x[OLT-61]
-	_ = x[OLE-62]
-	_ = x[OGE-63]
-	_ = x[OGT-64]
-	_ = x[ODEREF-65]
-	_ = x[OINDEX-66]
-	_ = x[OINDEXMAP-67]
-	_ = x[OKEY-68]
-	_ = x[OSTRUCTKEY-69]
-	_ = x[OLEN-70]
-	_ = x[OMAKE-71]
-	_ = x[OMAKECHAN-72]
-	_ = x[OMAKEMAP-73]
-	_ = x[OMAKESLICE-74]
-	_ = x[OMAKESLICECOPY-75]
-	_ = x[OMUL-76]
-	_ = x[ODIV-77]
-	_ = x[OMOD-78]
-	_ = x[OLSH-79]
-	_ = x[ORSH-80]
-	_ = x[OAND-81]
-	_ = x[OANDNOT-82]
-	_ = x[ONEW-83]
-	_ = x[ONOT-84]
-	_ = x[OBITNOT-85]
-	_ = x[OPLUS-86]
-	_ = x[ONEG-87]
-	_ = x[OOROR-88]
-	_ = x[OPANIC-89]
-	_ = x[OPRINT-90]
-	_ = x[OPRINTN-91]
-	_ = x[OPAREN-92]
-	_ = x[OSEND-93]
-	_ = x[OSLICE-94]
-	_ = x[OSLICEARR-95]
-	_ = x[OSLICESTR-96]
-	_ = x[OSLICE3-97]
-	_ = x[OSLICE3ARR-98]
-	_ = x[OSLICEHEADER-99]
-	_ = x[OSTRINGHEADER-100]
-	_ = x[ORECOVER-101]
-	_ = x[ORECOVERFP-102]
-	_ = x[ORECV-103]
-	_ = x[ORUNESTR-104]
-	_ = x[OSELRECV2-105]
-	_ = x[OREAL-106]
-	_ = x[OIMAG-107]
-	_ = x[OCOMPLEX-108]
-	_ = x[OALIGNOF-109]
-	_ = x[OOFFSETOF-110]
-	_ = x[OSIZEOF-111]
-	_ = x[OUNSAFEADD-112]
-	_ = x[OUNSAFESLICE-113]
-	_ = x[OUNSAFESLICEDATA-114]
-	_ = x[OUNSAFESTRING-115]
-	_ = x[OUNSAFESTRINGDATA-116]
-	_ = x[OMETHEXPR-117]
-	_ = x[OMETHVALUE-118]
-	_ = x[OBLOCK-119]
-	_ = x[OBREAK-120]
-	_ = x[OCASE-121]
-	_ = x[OCONTINUE-122]
-	_ = x[ODEFER-123]
-	_ = x[OFALL-124]
-	_ = x[OFOR-125]
-	_ = x[OGOTO-126]
-	_ = x[OIF-127]
-	_ = x[OLABEL-128]
-	_ = x[OGO-129]
-	_ = x[ORANGE-130]
-	_ = x[ORETURN-131]
-	_ = x[OSELECT-132]
-	_ = x[OSWITCH-133]
-	_ = x[OTYPESW-134]
-	_ = x[OFUNCINST-135]
-	_ = x[OINLCALL-136]
-	_ = x[OEFACE-137]
-	_ = x[OITAB-138]
-	_ = x[OIDATA-139]
-	_ = x[OSPTR-140]
-	_ = x[OCFUNC-141]
-	_ = x[OCHECKNIL-142]
-	_ = x[ORESULT-143]
-	_ = x[OINLMARK-144]
-	_ = x[OLINKSYMOFFSET-145]
-	_ = x[OJUMPTABLE-146]
-	_ = x[ODYNAMICDOTTYPE-147]
-	_ = x[ODYNAMICDOTTYPE2-148]
-	_ = x[ODYNAMICTYPE-149]
-	_ = x[OTAILCALL-150]
-	_ = x[OGETG-151]
-	_ = x[OGETCALLERPC-152]
-	_ = x[OGETCALLERSP-153]
-	_ = x[OEND-154]
+	_ = x[OCLEAR-34]
+	_ = x[OCLOSE-35]
+	_ = x[OCLOSURE-36]
+	_ = x[OCOMPLIT-37]
+	_ = x[OMAPLIT-38]
+	_ = x[OSTRUCTLIT-39]
+	_ = x[OARRAYLIT-40]
+	_ = x[OSLICELIT-41]
+	_ = x[OPTRLIT-42]
+	_ = x[OCONV-43]
+	_ = x[OCONVIFACE-44]
+	_ = x[OCONVIDATA-45]
+	_ = x[OCONVNOP-46]
+	_ = x[OCOPY-47]
+	_ = x[ODCL-48]
+	_ = x[ODCLFUNC-49]
+	_ = x[ODCLCONST-50]
+	_ = x[ODCLTYPE-51]
+	_ = x[ODELETE-52]
+	_ = x[ODOT-53]
+	_ = x[ODOTPTR-54]
+	_ = x[ODOTMETH-55]
+	_ = x[ODOTINTER-56]
+	_ = x[OXDOT-57]
+	_ = x[ODOTTYPE-58]
+	_ = x[ODOTTYPE2-59]
+	_ = x[OEQ-60]
+	_ = x[ONE-61]
+	_ = x[OLT-62]
+	_ = x[OLE-63]
+	_ = x[OGE-64]
+	_ = x[OGT-65]
+	_ = x[ODEREF-66]
+	_ = x[OINDEX-67]
+	_ = x[OINDEXMAP-68]
+	_ = x[OKEY-69]
+	_ = x[OSTRUCTKEY-70]
+	_ = x[OLEN-71]
+	_ = x[OMAKE-72]
+	_ = x[OMAKECHAN-73]
+	_ = x[OMAKEMAP-74]
+	_ = x[OMAKESLICE-75]
+	_ = x[OMAKESLICECOPY-76]
+	_ = x[OMUL-77]
+	_ = x[ODIV-78]
+	_ = x[OMOD-79]
+	_ = x[OLSH-80]
+	_ = x[ORSH-81]
+	_ = x[OAND-82]
+	_ = x[OANDNOT-83]
+	_ = x[ONEW-84]
+	_ = x[ONOT-85]
+	_ = x[OBITNOT-86]
+	_ = x[OPLUS-87]
+	_ = x[ONEG-88]
+	_ = x[OOROR-89]
+	_ = x[OPANIC-90]
+	_ = x[OPRINT-91]
+	_ = x[OPRINTN-92]
+	_ = x[OPAREN-93]
+	_ = x[OSEND-94]
+	_ = x[OSLICE-95]
+	_ = x[OSLICEARR-96]
+	_ = x[OSLICESTR-97]
+	_ = x[OSLICE3-98]
+	_ = x[OSLICE3ARR-99]
+	_ = x[OSLICEHEADER-100]
+	_ = x[OSTRINGHEADER-101]
+	_ = x[ORECOVER-102]
+	_ = x[ORECOVERFP-103]
+	_ = x[ORECV-104]
+	_ = x[ORUNESTR-105]
+	_ = x[OSELRECV2-106]
+	_ = x[OREAL-107]
+	_ = x[OIMAG-108]
+	_ = x[OCOMPLEX-109]
+	_ = x[OALIGNOF-110]
+	_ = x[OOFFSETOF-111]
+	_ = x[OSIZEOF-112]
+	_ = x[OUNSAFEADD-113]
+	_ = x[OUNSAFESLICE-114]
+	_ = x[OUNSAFESLICEDATA-115]
+	_ = x[OUNSAFESTRING-116]
+	_ = x[OUNSAFESTRINGDATA-117]
+	_ = x[OMETHEXPR-118]
+	_ = x[OMETHVALUE-119]
+	_ = x[OBLOCK-120]
+	_ = x[OBREAK-121]
+	_ = x[OCASE-122]
+	_ = x[OCONTINUE-123]
+	_ = x[ODEFER-124]
+	_ = x[OFALL-125]
+	_ = x[OFOR-126]
+	_ = x[OGOTO-127]
+	_ = x[OIF-128]
+	_ = x[OLABEL-129]
+	_ = x[OGO-130]
+	_ = x[ORANGE-131]
+	_ = x[ORETURN-132]
+	_ = x[OSELECT-133]
+	_ = x[OSWITCH-134]
+	_ = x[OTYPESW-135]
+	_ = x[OFUNCINST-136]
+	_ = x[OINLCALL-137]
+	_ = x[OEFACE-138]
+	_ = x[OITAB-139]
+	_ = x[OIDATA-140]
+	_ = x[OSPTR-141]
+	_ = x[OCFUNC-142]
+	_ = x[OCHECKNIL-143]
+	_ = x[ORESULT-144]
+	_ = x[OINLMARK-145]
+	_ = x[OLINKSYMOFFSET-146]
+	_ = x[OJUMPTABLE-147]
+	_ = x[ODYNAMICDOTTYPE-148]
+	_ = x[ODYNAMICDOTTYPE2-149]
+	_ = x[ODYNAMICTYPE-150]
+	_ = x[OTAILCALL-151]
+	_ = x[OGETG-152]
+	_ = x[OGETCALLERPC-153]
+	_ = x[OGETCALLERSP-154]
+	_ = x[OEND-155]
 }

-const _Op_name = "XXXNAMENONAMETYPELITERALNILADDSUBORXORADDSTRADDRANDANDAPPENDBYTES2STRBYTES2STRTMPRUNES2STRSTR2BYTESSTR2BYTESTMPSTR2RUNESSLICE2ARRSLICE2ARRPTRASAS2AS2DOTTYPEAS2FUNCAS2MAPRAS2RECVASOPCALLCALLFUNCCALLMETHCALLINTERCAPCLOSECLOSURECOMPLITMAPLITSTRUCTLITARRAYLITSLICELITPTRLITCONVCONVIFACECONVIDATACONVNOPCOPYDCLDCLFUNCDCLCONSTDCLTYPEDELETEDOTDOTPTRDOTMETHDOTINTERXDOTDOTTYPEDOTTYPE2EQNELTLEGEGTDEREFINDEXINDEXMAPKEYSTRUCTKEYLENMAKEMAKECHANMAKEMAPMAKESLICEMAKESLICECOPYMULDIVMODLSHRSHANDANDNOTNEWNOTBITNOTPLUSNEGORORPANICPRINTPRINTNPARENSENDSLICESLICEARRSLICESTRSLICE3SLICE3ARRSLICEHEADERSTRINGHEADERRECOVERRECOVERFPRECVRUNESTRSELRECV2REALIMAGCOMPLEXALIGNOFOFFSETOFSIZEOFUNSAFEADDUNSAFESLICEUNSAFESLICEDATAUNSAFESTRINGUNSAFESTRINGDATAMETHEXPRMETHVALUEBLOCKBREAKCASECONTINUEDEFERFALLFORGOTOIFLABELGORANGERETURNSELECTSWITCHTYPESWFUNCINSTINLCALLEFACEITABIDATASPTRCFUNCCHECKNILRESULTINLMARKLINKSYMOFFSETJUMPTABLEDYNAMICDOTTYPEDYNAMICDOTTYPE2DYNAMICTYPETAILCALLGETGGETCALLERPCGETCALLERSPEND"
+const _Op_name = "XXXNAMENONAMETYPELITERALNILADDSUBORXORADDSTRADDRANDANDAPPENDBYTES2STRBYTES2STRTMPRUNES2STRSTR2BYTESSTR2BYTESTMPSTR2RUNESSLICE2ARRSLICE2ARRPTRASAS2AS2DOTTYPEAS2FUNCAS2MAPRAS2RECVASOPCALLCALLFUNCCALLMETHCALLINTERCAPCLEARCLOSECLOSURECOMPLITMAPLITSTRUCTLITARRAYLITSLICELITPTRLITCONVCONVIFACECONVIDATACONVNOPCOPYDCLDCLFUNCDCLCONSTDCLTYPEDELETEDOTDOTPTRDOTMETHDOTINTERXDOTDOTTYPEDOTTYPE2EQNELTLEGEGTDEREFINDEXINDEXMAPKEYSTRUCTKEYLENMAKEMAKECHANMAKEMAPMAKESLICEMAKESLICECOPYMULDIVMODLSHRSHANDANDNOTNEWNOTBITNOTPLUSNEGORORPANICPRINTPRINTNPARENSENDSLICESLICEARRSLICESTRSLICE3SLICE3ARRSLICEHEADERSTRINGHEADERRECOVERRECOVERFPRECVRUNESTRSELRECV2REALIMAGCOMPLEXALIGNOFOFFSETOFSIZEOFUNSAFEADDUNSAFESLICEUNSAFESLICEDATAUNSAFESTRINGUNSAFESTRINGDATAMETHEXPRMETHVALUEBLOCKBREAKCASECONTINUEDEFERFALLFORGOTOIFLABELGORANGERETURNSELECTSWITCHTYPESWFUNCINSTINLCALLEFACEITABIDATASPTRCFUNCCHECKNILRESULTINLMARKLINKSYMOFFSETJUMPTABLEDYNAMICDOTTYPEDYNAMICDOTTYPE2DYNAMICTYPETAILCALLGETGGETCALLERPCGETCALLERSPEND"

-var _Op_index = [...]uint16{0, 3, 7, 13, 17, 24, 27, 30, 33, 35, 38, 44, 48, 54, 60, 69, 81, 90, 99, 111, 120, 129, 141, 143, 146, 156, 163, 170, 177, 181, 185, 193, 201, 210, 213, 218, 225, 232, 238, 247, 255, 263, 269, 273, 282, 291, 298, 302, 305, 312, 320, 327, 333, 336, 342, 349, 357, 361, 368, 376, 378, 380, 382, 384, 386, 388, 393, 398, 406, 409, 418, 421, 425, 433, 440, 449, 462, 465, 468, 471, 474, 477, 480, 486, 489, 492, 498, 502, 505, 509, 514, 519, 525, 530, 534, 539, 547, 555, 561, 570, 581, 593, 600, 609, 613, 620, 628, 632, 636, 643, 650, 658, 664, 673, 684, 699, 711, 727, 735, 744, 749, 754, 758, 766, 771, 775, 778, 782, 784, 789, 791, 796, 802, 808, 814, 820, 828, 835, 840, 844, 849, 853, 858, 866, 872, 879, 892, 901, 915, 930, 941, 949, 953, 964, 975, 978}
+var _Op_index = [...]uint16{0, 3, 7, 13, 17, 24, 27, 30, 33, 35, 38, 44, 48, 54, 60, 69, 81, 90, 99, 111, 120, 129, 141, 143, 146, 156, 163, 170, 177, 181, 185, 193, 201, 210, 213, 218, 223, 230, 237, 243, 252, 260, 268, 274, 278, 287, 296, 303, 307, 310, 317, 325, 332, 338, 341, 347, 354, 362, 366, 373, 381, 383, 385, 387, 389, 391, 393, 398, 403, 411, 414, 423, 426, 430, 438, 445, 454, 467, 470, 473, 476, 479, 482, 485, 491, 494, 497, 503, 507, 510, 514, 519, 524, 530, 535, 539, 544, 552, 560, 566, 575, 586, 598, 605, 614, 618, 625, 633, 637, 641, 648, 655, 663, 669, 678, 689, 704, 716, 732, 740, 749, 754, 759, 763, 771, 776, 780, 783, 787, 789, 794, 796, 801, 807, 813, 819, 825, 833, 840, 845, 849, 854, 858, 863, 871, 877, 884, 897, 906, 920, 935, 946, 954, 958, 969, 980, 983}

 func (i Op) String() string {
 	if i >= Op(len(_Op_index)-1) {
--- a/src/cmd/compile/internal/typecheck/const.go
+++ b/src/cmd/compile/internal/typecheck/const.go
@ -743,6 +743,7 @@ func callOrChan(n ir.Node) bool {
 		ir.OCALLINTER,
 		ir.OCALLMETH,
 		ir.OCAP,
+		ir.OCLEAR,
 		ir.OCLOSE,
 		ir.OCOMPLEX,
 		ir.OCOPY,
--- a/src/cmd/compile/internal/typecheck/func.go
+++ b/src/cmd/compile/internal/typecheck/func.go
@ -260,7 +260,7 @@ func tcCall(n *ir.CallExpr, top int) ir.Node {
 			n.SetTypecheck(0) // re-typechecking new op is OK, not a loop
 			return typecheck(n, top)

-		case ir.OCAP, ir.OCLOSE, ir.OIMAG, ir.OLEN, ir.OPANIC, ir.OREAL, ir.OUNSAFESTRINGDATA, ir.OUNSAFESLICEDATA:
+		case ir.OCAP, ir.OCLEAR, ir.OCLOSE, ir.OIMAG, ir.OLEN, ir.OPANIC, ir.OREAL, ir.OUNSAFESTRINGDATA, ir.OUNSAFESLICEDATA:
 			typecheckargs(n)
 			fallthrough
 		case ir.ONEW, ir.OALIGNOF, ir.OOFFSETOF, ir.OSIZEOF:
@ -441,6 +441,28 @@ func tcAppend(n *ir.CallExpr) ir.Node {
 	return n
 }

+// tcClear typechecks an OCLEAR node.
+func tcClear(n *ir.UnaryExpr) ir.Node {
+	n.X = Expr(n.X)
+	n.X = DefaultLit(n.X, nil)
+	l := n.X
+	t := l.Type()
+	if t == nil {
+		n.SetType(nil)
+		return n
+	}
+
+	switch {
+	case t.IsMap(), t.IsSlice():
+	default:
+		base.Errorf("invalid operation: %v (argument must be a map or slice)", n)
+		n.SetType(nil)
+		return n
+	}
+
+	return n
+}
+
 // tcClose typechecks an OCLOSE node.
 func tcClose(n *ir.UnaryExpr) ir.Node {
 	n.X = Expr(n.X)
--- a/src/cmd/compile/internal/typecheck/stmt.go
+++ b/src/cmd/compile/internal/typecheck/stmt.go
@ -273,6 +273,7 @@ func tcGoDefer(n *ir.GoDeferStmt) {
 	case ir.OCALLINTER,
 		ir.OCALLMETH,
 		ir.OCALLFUNC,
+		ir.OCLEAR,
 		ir.OCLOSE,
 		ir.OCOPY,
 		ir.ODELETE,
--- a/src/cmd/compile/internal/typecheck/typecheck.go
+++ b/src/cmd/compile/internal/typecheck/typecheck.go
@ -336,7 +336,7 @@ func typecheck(n ir.Node, top int) (res ir.Node) {
 	case ir.OAPPEND:
 		// Must be used (and not BinaryExpr/UnaryExpr).
 		isStmt = false
-	case ir.OCLOSE, ir.ODELETE, ir.OPANIC, ir.OPRINT, ir.OPRINTN:
+	case ir.OCLEAR, ir.OCLOSE, ir.ODELETE, ir.OPANIC, ir.OPRINT, ir.OPRINTN:
 		// Must not be used.
 		isExpr = false
 		isStmt = true
@ -621,6 +621,10 @@ func typecheck1(n ir.Node, top int) ir.Node {
 		n := n.(*ir.BinaryExpr)
 		return tcComplex(n)

+	case ir.OCLEAR:
+		n := n.(*ir.UnaryExpr)
+		return tcClear(n)
+
 	case ir.OCLOSE:
 		n := n.(*ir.UnaryExpr)
 		return tcClose(n)
--- a/src/cmd/compile/internal/typecheck/universe.go
+++ b/src/cmd/compile/internal/typecheck/universe.go
@ -34,6 +34,7 @@ var builtinFuncs = [...]struct {
 }{
 	{"append", ir.OAPPEND},
 	{"cap", ir.OCAP},
+	{"clear", ir.OCLEAR},
 	{"close", ir.OCLOSE},
 	{"complex", ir.OCOMPLEX},
 	{"copy", ir.OCOPY},
--- a/src/cmd/compile/internal/walk/builtin.go
+++ b/src/cmd/compile/internal/walk/builtin.go
@ -130,6 +130,18 @@ func walkAppend(n *ir.CallExpr, init *ir.Nodes, dst ir.Node) ir.Node {
 	return s
 }

+// walkClear walks an OCLEAR node.
+func walkClear(n *ir.UnaryExpr) ir.Node {
+	typ := n.X.Type()
+	switch {
+	case typ.IsSlice():
+		return arrayClear(n.X.Pos(), n.X, nil)
+	case typ.IsMap():
+		return mapClear(n.X, reflectdata.TypePtrAt(n.X.Pos(), n.X.Type()))
+	}
+	panic("unreachable")
+}
+
 // walkClose walks an OCLOSE node.
 func walkClose(n *ir.UnaryExpr, init *ir.Nodes) ir.Node {
 	// cannot use chanfn - closechan takes any, not chan any
--- a/src/cmd/compile/internal/walk/expr.go
+++ b/src/cmd/compile/internal/walk/expr.go
@ -279,6 +279,10 @@ func walkExpr1(n ir.Node, init *ir.Nodes) ir.Node {
 	case ir.OCOPY:
 		return walkCopy(n.(*ir.BinaryExpr), init, base.Flag.Cfg.Instrumenting && !base.Flag.CompilingRuntime)

+	case ir.OCLEAR:
+		n := n.(*ir.UnaryExpr)
+		return walkClear(n)
+
 	case ir.OCLOSE:
 		n := n.(*ir.UnaryExpr)
 		return walkClose(n, init)
--- a/src/cmd/compile/internal/walk/order.go
+++ b/src/cmd/compile/internal/walk/order.go
@ -740,7 +740,7 @@ func (o *orderState) stmt(n ir.Node) {
 			}
 		}

-	case ir.OCHECKNIL, ir.OCLOSE, ir.OPANIC, ir.ORECV:
+	case ir.OCHECKNIL, ir.OCLEAR, ir.OCLOSE, ir.OPANIC, ir.ORECV:
 		n := n.(*ir.UnaryExpr)
 		t := o.markTemp()
 		n.X = o.expr(n.X, nil)
--- a/src/cmd/compile/internal/walk/range.go
+++ b/src/cmd/compile/internal/walk/range.go
@ -13,6 +13,7 @@ import (
 	"cmd/compile/internal/ssagen"
 	"cmd/compile/internal/typecheck"
 	"cmd/compile/internal/types"
+	"cmd/internal/src"
 	"cmd/internal/sys"
 )

@ -38,7 +39,7 @@ func cheapComputableIndex(width int64) bool {
 // the returned node.
 func walkRange(nrange *ir.RangeStmt) ir.Node {
 	if isMapClear(nrange) {
-		return mapClear(nrange)
+		return mapRangeClear(nrange)
 	}

 	nfor := ir.NewForStmt(nrange.Pos(), nil, nil, nil, nil)
@ -77,7 +78,7 @@ func walkRange(nrange *ir.RangeStmt) ir.Node {
 		base.Fatalf("walkRange")

 	case types.TARRAY, types.TSLICE, types.TPTR: // TPTR is pointer-to-array
-		if nn := arrayClear(nrange, v1, v2, a); nn != nil {
+		if nn := arrayRangeClear(nrange, v1, v2, a); nn != nil {
 			base.Pos = lno
 			return nn
 		}
@ -437,18 +438,23 @@ func isMapClear(n *ir.RangeStmt) bool {
 	return true
 }

-// mapClear constructs a call to runtime.mapclear for the map m.
-func mapClear(nrange *ir.RangeStmt) ir.Node {
+// mapRangeClear constructs a call to runtime.mapclear for the map range idiom.
+func mapRangeClear(nrange *ir.RangeStmt) ir.Node {
 	m := nrange.X
 	origPos := ir.SetPos(m)
 	defer func() { base.Pos = origPos }()

+	return mapClear(m, reflectdata.RangeMapRType(base.Pos, nrange))
+}
+
+// mapClear constructs a call to runtime.mapclear for the map m.
+func mapClear(m, rtyp ir.Node) ir.Node {
 	t := m.Type()

 	// instantiate mapclear(typ *type, hmap map[any]any)
 	fn := typecheck.LookupRuntime("mapclear")
 	fn = typecheck.SubstArgTypes(fn, t.Key(), t.Elem())
-	n := mkcallstmt1(fn, reflectdata.RangeMapRType(base.Pos, nrange), m)
+	n := mkcallstmt1(fn, rtyp, m)
 	return walkStmt(typecheck.Stmt(n))
 }

@ -463,7 +469,7 @@ func mapClear(nrange *ir.RangeStmt) ir.Node {
 // in which the evaluation of a is side-effect-free.
 //
 // Parameters are as in walkRange: "for v1, v2 = range a".
-func arrayClear(loop *ir.RangeStmt, v1, v2, a ir.Node) ir.Node {
+func arrayRangeClear(loop *ir.RangeStmt, v1, v2, a ir.Node) ir.Node {
 	if base.Flag.N != 0 || base.Flag.Cfg.Instrumenting {
 		return nil
 	}
@ -496,8 +502,17 @@ func arrayClear(loop *ir.RangeStmt, v1, v2, a ir.Node) ir.Node {
 		return nil
 	}

-	elemsize := typecheck.RangeExprType(loop.X.Type()).Elem().Size()
-	if elemsize <= 0 || !ir.IsZero(stmt.Y) {
+	if !ir.IsZero(stmt.Y) {
+		return nil
+	}
+
+	return arrayClear(stmt.Pos(), a, loop)
+}
+
+// arrayClear constructs a call to runtime.memclr for fast zeroing of slices and arrays.
+func arrayClear(wbPos src.XPos, a ir.Node, nrange *ir.RangeStmt) ir.Node {
+	elemsize := typecheck.RangeExprType(a.Type()).Elem().Size()
+	if elemsize <= 0 {
 		return nil
 	}

@ -527,7 +542,7 @@ func arrayClear(loop *ir.RangeStmt, v1, v2, a ir.Node) ir.Node {
 	var fn ir.Node
 	if a.Type().Elem().HasPointers() {
 		// memclrHasPointers(hp, hn)
-		ir.CurFunc.SetWBPos(stmt.Pos())
+		ir.CurFunc.SetWBPos(wbPos)
 		fn = mkcallstmt("memclrHasPointers", hp, hn)
 	} else {
 		// memclrNoHeapPointers(hp, hn)
@ -536,10 +551,11 @@ func arrayClear(loop *ir.RangeStmt, v1, v2, a ir.Node) ir.Node {

 	n.Body.Append(fn)

-	// i = len(a) - 1
-	v1 = ir.NewAssignStmt(base.Pos, v1, ir.NewBinaryExpr(base.Pos, ir.OSUB, ir.NewUnaryExpr(base.Pos, ir.OLEN, a), ir.NewInt(1)))
-
-	n.Body.Append(v1)
+	// For array range clear, also set "i = len(a) - 1"
+	if nrange != nil {
+		idx := ir.NewAssignStmt(base.Pos, nrange.Key, ir.NewBinaryExpr(base.Pos, ir.OSUB, ir.NewUnaryExpr(base.Pos, ir.OLEN, a), ir.NewInt(1)))
+		n.Body.Append(idx)
+	}

 	n.Cond = typecheck.Expr(n.Cond)
 	n.Cond = typecheck.DefaultLit(n.Cond, nil)
--- a/src/cmd/compile/internal/walk/stmt.go
+++ b/src/cmd/compile/internal/walk/stmt.go
@ -39,6 +39,7 @@ func walkStmt(n ir.Node) ir.Node {
 		ir.OAS2RECV,
 		ir.OAS2FUNC,
 		ir.OAS2MAPR,
+		ir.OCLEAR,
 		ir.OCLOSE,
 		ir.OCOPY,
 		ir.OCALLINTER,
--- a/test/clear.go
+++ b/test/clear.go
@ -0,0 +1,47 @@
+// run
+
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import "math"
+
+func checkClearSlice() {
+	s := []int{1, 2, 3}
+	clear(s)
+	for i := range s {
+		if s[i] != 0 {
+			panic("clear not zeroing slice elem")
+		}
+	}
+
+	clear([]int{})
+}
+
+func checkClearMap() {
+	m1 := make(map[int]int)
+	m1[0] = 0
+	m1[1] = 1
+	clear(m1)
+	if len(m1) != 0 {
+		panic("m1 is not cleared")
+	}
+
+	// map contains NaN keys is also cleared.
+	m2 := make(map[float64]int)
+	m2[math.NaN()] = 1
+	m2[math.NaN()] = 1
+	clear(m2)
+	if len(m2) != 0 {
+		panic("m2 is not cleared")
+	}
+
+	clear(map[int]int{})
+}
+
+func main() {
+	checkClearSlice()
+	checkClearMap()
+}