cmd/compile: add ORESULT, remove OINDREGSP

This change is mostly cosmetic.

OINDREGSP was used only for reading the results of a function call.
In recognition of that fact, rename it to ORESULT.
Along the way, trim down our handling of it to the bare minimum,
and rely on the increased clarity of ORESULT to inline nodarg.

Passes toolstash-check.

Change-Id: I25b177df4ea54a8e94b1698d044c297b7e453c64
Reviewed-on: https://go-review.googlesource.com/c/go/+/170705
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

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

@@ -1579,9 +1579,6 @@ func (n *Node) nodedump(s fmt.State, flag FmtFlag, mode fmtMode) {
 	default:
 		mode.Fprintf(s, "%v%j", n.Op, n)
 
-	case OINDREGSP:
-		mode.Fprintf(s, "%v-SP%j", n.Op, n)
-
 	case OLITERAL:
 		mode.Fprintf(s, "%v-%v%j", n.Op, n.Val(), n)
 

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

@@ -4,9 +4,169 @@ package gc
 
 import "strconv"
 
-const _Op_name = "XXXNAMENONAMETYPEPACKLITERALADDSUBORXORADDSTRADDRANDANDAPPENDBYTES2STRBYTES2STRTMPRUNES2STRSTR2BYTESSTR2BYTESTMPSTR2RUNESASAS2AS2FUNCAS2RECVAS2MAPRAS2DOTTYPEASOPCALLCALLFUNCCALLMETHCALLINTERCALLPARTCAPCLOSECLOSURECOMPLITMAPLITSTRUCTLITARRAYLITSLICELITPTRLITCONVCONVIFACECONVNOPCOPYDCLDCLFUNCDCLFIELDDCLCONSTDCLTYPEDELETEDOTDOTPTRDOTMETHDOTINTERXDOTDOTTYPEDOTTYPE2EQNELTLEGEGTDEREFINDEXINDEXMAPKEYSTRUCTKEYLENMAKEMAKECHANMAKEMAPMAKESLICEMULDIVMODLSHRSHANDANDNOTNEWNEWOBJNOTBITNOTPLUSNEGORORPANICPRINTPRINTNPARENSENDSLICESLICEARRSLICESTRSLICE3SLICE3ARRSLICEHEADERRECOVERRECVRUNESTRSELRECVSELRECV2IOTAREALIMAGCOMPLEXALIGNOFOFFSETOFSIZEOFBLOCKBREAKCASEXCASECONTINUEDEFEREMPTYFALLFORFORUNTILGOTOIFLABELGORANGERETURNSELECTSWITCHTYPESWTCHANTMAPTSTRUCTTINTERTFUNCTARRAYDDDDDDARGINLCALLEFACEITABIDATASPTRCLOSUREVARCFUNCCHECKNILVARDEFVARKILLVARLIVEINDREGSPINLMARKRETJMPGETGEND"
+func _() {
+	// An "invalid array index" compiler error signifies that the constant values have changed.
+	// Re-run the stringer command to generate them again.
+	var x [1]struct{}
+	_ = x[OXXX-0]
+	_ = x[ONAME-1]
+	_ = x[ONONAME-2]
+	_ = x[OTYPE-3]
+	_ = x[OPACK-4]
+	_ = x[OLITERAL-5]
+	_ = x[OADD-6]
+	_ = x[OSUB-7]
+	_ = x[OOR-8]
+	_ = x[OXOR-9]
+	_ = x[OADDSTR-10]
+	_ = x[OADDR-11]
+	_ = x[OANDAND-12]
+	_ = x[OAPPEND-13]
+	_ = x[OBYTES2STR-14]
+	_ = x[OBYTES2STRTMP-15]
+	_ = x[ORUNES2STR-16]
+	_ = x[OSTR2BYTES-17]
+	_ = x[OSTR2BYTESTMP-18]
+	_ = x[OSTR2RUNES-19]
+	_ = x[OAS-20]
+	_ = x[OAS2-21]
+	_ = x[OAS2FUNC-22]
+	_ = x[OAS2RECV-23]
+	_ = x[OAS2MAPR-24]
+	_ = x[OAS2DOTTYPE-25]
+	_ = x[OASOP-26]
+	_ = x[OCALL-27]
+	_ = x[OCALLFUNC-28]
+	_ = x[OCALLMETH-29]
+	_ = x[OCALLINTER-30]
+	_ = x[OCALLPART-31]
+	_ = x[OCAP-32]
+	_ = x[OCLOSE-33]
+	_ = x[OCLOSURE-34]
+	_ = x[OCOMPLIT-35]
+	_ = x[OMAPLIT-36]
+	_ = x[OSTRUCTLIT-37]
+	_ = x[OARRAYLIT-38]
+	_ = x[OSLICELIT-39]
+	_ = x[OPTRLIT-40]
+	_ = x[OCONV-41]
+	_ = x[OCONVIFACE-42]
+	_ = x[OCONVNOP-43]
+	_ = x[OCOPY-44]
+	_ = x[ODCL-45]
+	_ = x[ODCLFUNC-46]
+	_ = x[ODCLFIELD-47]
+	_ = x[ODCLCONST-48]
+	_ = x[ODCLTYPE-49]
+	_ = x[ODELETE-50]
+	_ = x[ODOT-51]
+	_ = x[ODOTPTR-52]
+	_ = x[ODOTMETH-53]
+	_ = x[ODOTINTER-54]
+	_ = x[OXDOT-55]
+	_ = x[ODOTTYPE-56]
+	_ = x[ODOTTYPE2-57]
+	_ = x[OEQ-58]
+	_ = x[ONE-59]
+	_ = x[OLT-60]
+	_ = x[OLE-61]
+	_ = x[OGE-62]
+	_ = x[OGT-63]
+	_ = x[ODEREF-64]
+	_ = x[OINDEX-65]
+	_ = x[OINDEXMAP-66]
+	_ = x[OKEY-67]
+	_ = x[OSTRUCTKEY-68]
+	_ = x[OLEN-69]
+	_ = x[OMAKE-70]
+	_ = x[OMAKECHAN-71]
+	_ = x[OMAKEMAP-72]
+	_ = x[OMAKESLICE-73]
+	_ = x[OMUL-74]
+	_ = x[ODIV-75]
+	_ = x[OMOD-76]
+	_ = x[OLSH-77]
+	_ = x[ORSH-78]
+	_ = x[OAND-79]
+	_ = x[OANDNOT-80]
+	_ = x[ONEW-81]
+	_ = x[ONEWOBJ-82]
+	_ = x[ONOT-83]
+	_ = x[OBITNOT-84]
+	_ = x[OPLUS-85]
+	_ = x[ONEG-86]
+	_ = x[OOROR-87]
+	_ = x[OPANIC-88]
+	_ = x[OPRINT-89]
+	_ = x[OPRINTN-90]
+	_ = x[OPAREN-91]
+	_ = x[OSEND-92]
+	_ = x[OSLICE-93]
+	_ = x[OSLICEARR-94]
+	_ = x[OSLICESTR-95]
+	_ = x[OSLICE3-96]
+	_ = x[OSLICE3ARR-97]
+	_ = x[OSLICEHEADER-98]
+	_ = x[ORECOVER-99]
+	_ = x[ORECV-100]
+	_ = x[ORUNESTR-101]
+	_ = x[OSELRECV-102]
+	_ = x[OSELRECV2-103]
+	_ = x[OIOTA-104]
+	_ = x[OREAL-105]
+	_ = x[OIMAG-106]
+	_ = x[OCOMPLEX-107]
+	_ = x[OALIGNOF-108]
+	_ = x[OOFFSETOF-109]
+	_ = x[OSIZEOF-110]
+	_ = x[OBLOCK-111]
+	_ = x[OBREAK-112]
+	_ = x[OCASE-113]
+	_ = x[OXCASE-114]
+	_ = x[OCONTINUE-115]
+	_ = x[ODEFER-116]
+	_ = x[OEMPTY-117]
+	_ = x[OFALL-118]
+	_ = x[OFOR-119]
+	_ = x[OFORUNTIL-120]
+	_ = x[OGOTO-121]
+	_ = x[OIF-122]
+	_ = x[OLABEL-123]
+	_ = x[OGO-124]
+	_ = x[ORANGE-125]
+	_ = x[ORETURN-126]
+	_ = x[OSELECT-127]
+	_ = x[OSWITCH-128]
+	_ = x[OTYPESW-129]
+	_ = x[OTCHAN-130]
+	_ = x[OTMAP-131]
+	_ = x[OTSTRUCT-132]
+	_ = x[OTINTER-133]
+	_ = x[OTFUNC-134]
+	_ = x[OTARRAY-135]
+	_ = x[ODDD-136]
+	_ = x[ODDDARG-137]
+	_ = x[OINLCALL-138]
+	_ = x[OEFACE-139]
+	_ = x[OITAB-140]
+	_ = x[OIDATA-141]
+	_ = x[OSPTR-142]
+	_ = x[OCLOSUREVAR-143]
+	_ = x[OCFUNC-144]
+	_ = x[OCHECKNIL-145]
+	_ = x[OVARDEF-146]
+	_ = x[OVARKILL-147]
+	_ = x[OVARLIVE-148]
+	_ = x[ORESULT-149]
+	_ = x[OINLMARK-150]
+	_ = x[ORETJMP-151]
+	_ = x[OGETG-152]
+	_ = x[OEND-153]
+}
+
+const _Op_name = "XXXNAMENONAMETYPEPACKLITERALADDSUBORXORADDSTRADDRANDANDAPPENDBYTES2STRBYTES2STRTMPRUNES2STRSTR2BYTESSTR2BYTESTMPSTR2RUNESASAS2AS2FUNCAS2RECVAS2MAPRAS2DOTTYPEASOPCALLCALLFUNCCALLMETHCALLINTERCALLPARTCAPCLOSECLOSURECOMPLITMAPLITSTRUCTLITARRAYLITSLICELITPTRLITCONVCONVIFACECONVNOPCOPYDCLDCLFUNCDCLFIELDDCLCONSTDCLTYPEDELETEDOTDOTPTRDOTMETHDOTINTERXDOTDOTTYPEDOTTYPE2EQNELTLEGEGTDEREFINDEXINDEXMAPKEYSTRUCTKEYLENMAKEMAKECHANMAKEMAPMAKESLICEMULDIVMODLSHRSHANDANDNOTNEWNEWOBJNOTBITNOTPLUSNEGORORPANICPRINTPRINTNPARENSENDSLICESLICEARRSLICESTRSLICE3SLICE3ARRSLICEHEADERRECOVERRECVRUNESTRSELRECVSELRECV2IOTAREALIMAGCOMPLEXALIGNOFOFFSETOFSIZEOFBLOCKBREAKCASEXCASECONTINUEDEFEREMPTYFALLFORFORUNTILGOTOIFLABELGORANGERETURNSELECTSWITCHTYPESWTCHANTMAPTSTRUCTTINTERTFUNCTARRAYDDDDDDARGINLCALLEFACEITABIDATASPTRCLOSUREVARCFUNCCHECKNILVARDEFVARKILLVARLIVERESULTINLMARKRETJMPGETGEND"
 
-var _Op_index = [...]uint16{0, 3, 7, 13, 17, 21, 28, 31, 34, 36, 39, 45, 49, 55, 61, 70, 82, 91, 100, 112, 121, 123, 126, 133, 140, 147, 157, 161, 165, 173, 181, 190, 198, 201, 206, 213, 220, 226, 235, 243, 251, 257, 261, 270, 277, 281, 284, 291, 299, 307, 314, 320, 323, 329, 336, 344, 348, 355, 363, 365, 367, 369, 371, 373, 375, 380, 385, 393, 396, 405, 408, 412, 420, 427, 436, 439, 442, 445, 448, 451, 454, 460, 463, 469, 472, 478, 482, 485, 489, 494, 499, 505, 510, 514, 519, 527, 535, 541, 550, 561, 568, 572, 579, 586, 594, 598, 602, 606, 613, 620, 628, 634, 639, 644, 648, 653, 661, 666, 671, 675, 678, 686, 690, 692, 697, 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, 853, 859, 863, 866}
+var _Op_index = [...]uint16{0, 3, 7, 13, 17, 21, 28, 31, 34, 36, 39, 45, 49, 55, 61, 70, 82, 91, 100, 112, 121, 123, 126, 133, 140, 147, 157, 161, 165, 173, 181, 190, 198, 201, 206, 213, 220, 226, 235, 243, 251, 257, 261, 270, 277, 281, 284, 291, 299, 307, 314, 320, 323, 329, 336, 344, 348, 355, 363, 365, 367, 369, 371, 373, 375, 380, 385, 393, 396, 405, 408, 412, 420, 427, 436, 439, 442, 445, 448, 451, 454, 460, 463, 469, 472, 478, 482, 485, 489, 494, 499, 505, 510, 514, 519, 527, 535, 541, 550, 561, 568, 572, 579, 586, 594, 598, 602, 606, 613, 620, 628, 634, 639, 644, 648, 653, 661, 666, 671, 675, 678, 686, 690, 692, 697, 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, 844, 851, 857, 861, 864}
 
 func (i Op) String() string {
 	if i >= Op(len(_Op_index)-1) {

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

@@ -2276,7 +2276,7 @@ func (s *state) expr(n *Node) *ssa.Value {
 	case OADDR:
 		return s.addr(n.Left, n.Bounded())
 
-	case OINDREGSP:
+	case ORESULT:
 		addr := s.constOffPtrSP(types.NewPtr(n.Type), n.Xoffset)
 		return s.load(n.Type, addr)
 
@@ -3929,9 +3929,8 @@ func (s *state) addr(n *Node, bounded bool) *ssa.Value {
 			s.Fatalf("variable address class %v not implemented", n.Class())
 			return nil
 		}
-	case OINDREGSP:
-		// indirect off REGSP
-		// used for storing/loading arguments/returns to/from callees
+	case ORESULT:
+		// load return from callee
 		return s.constOffPtrSP(t, n.Xoffset)
 	case OINDEX:
 		if n.Left.Type.IsSlice() {

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

@@ -43,7 +43,7 @@ type Node struct {
 
 	// Various. Usually an offset into a struct. For example:
 	// - ONAME nodes that refer to local variables use it to identify their stack frame position.
-	// - ODOT, ODOTPTR, and OINDREGSP use it to indicate offset relative to their base address.
+	// - ODOT, ODOTPTR, and ORESULT use it to indicate offset relative to their base address.
 	// - OSTRUCTKEY uses it to store the named field's offset.
 	// - Named OLITERALs use it to store their ambient iota value.
 	// - OINLMARK stores an index into the inlTree data structure.
@@ -751,7 +751,7 @@ const (
 	OVARDEF     // variable is about to be fully initialized
 	OVARKILL    // variable is dead
 	OVARLIVE    // variable is alive
-	OINDREGSP   // offset plus indirect of REGSP, such as 8(SP).
+	ORESULT     // result of a function call; Xoffset is stack offset
 	OINLMARK    // start of an inlined body, with file/line of caller. Xoffset is an index into the inline tree.
 
 	// arch-specific opcodes

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

@@ -481,7 +481,7 @@ opswitch:
 		Dump("walk", n)
 		Fatalf("walkexpr: switch 1 unknown op %+S", n)
 
-	case ONONAME, OINDREGSP, OEMPTY, OGETG, ONEWOBJ:
+	case ONONAME, OEMPTY, OGETG, ONEWOBJ:
 
 	case OTYPE, ONAME, OLITERAL:
 		// TODO(mdempsky): Just return n; see discussion on CL 38655.
@@ -1674,7 +1674,12 @@ func ascompatet(nl Nodes, nr *types.Type) []*Node {
 			l = tmp
 		}
 
-		a := nod(OAS, l, nodarg(r))
+		res := nod(ORESULT, nil, nil)
+		res.Xoffset = Ctxt.FixedFrameSize() + r.Offset
+		res.Type = r.Type
+		res.SetTypecheck(1)
+
+		a := nod(OAS, l, res)
 		a = convas(a, &nn)
 		updateHasCall(a)
 		if a.HasCall() {
@@ -1687,32 +1692,6 @@ func ascompatet(nl Nodes, nr *types.Type) []*Node {
 	return append(nn.Slice(), mm.Slice()...)
 }
 
-// nodarg returns a Node for the function argument f.
-// f is a *types.Field within a struct *types.Type.
-//
-// The node is for use by a caller invoking the given
-// function, preparing the arguments before the call
-// or retrieving the results after the call.
-// In this case, the node will correspond to an outgoing argument
-// slot like 8(SP).
-func nodarg(f *types.Field) *Node {
-	// Build fake name for individual variable.
-	n := newname(lookup("__"))
-	n.Type = f.Type
-	if f.Offset == BADWIDTH {
-		Fatalf("nodarg: offset not computed for %v", f)
-	}
-	n.Xoffset = f.Offset
-	n.Orig = asNode(f.Nname)
-
-	// preparing arguments for call
-	n.Op = OINDREGSP
-	n.Xoffset += Ctxt.FixedFrameSize()
-	n.SetTypecheck(1)
-	n.SetAddrtaken(true) // keep optimizers at bay
-	return n
-}
-
 // package all the arguments that match a ... T parameter into a []T.
 func mkdotargslice(typ *types.Type, args []*Node, init *Nodes, ddd *Node) *Node {
 	esc := uint16(EscUnknown)