cmd/cc, cmd/gc: stop generating 'argsize' PCDATA

The argsize PCDATA was specifying the number of
bytes passed to a function call, so that if the function
did not specify its argument count, the garbage collector
could use the call site information to scan those bytes
conservatively. We don't do that anymore, so stop
generating the information.

LGTM=khr
R=khr
CC=golang-codereviews
https://golang.org/cl/139530043

src/cmd/5c/cgen.c

@@ -366,14 +366,12 @@ _cgen(Node *n, Node *nn, int inrel)
 		if(REGARG >= 0)
 			o = reg[REGARG];
 		gargs(r, &nod, &nod1);
-		gpcdata(PCDATA_ArgSize, curarg);
 		if(l->addable < INDEXED) {
 			reglcgen(&nod, l, Z);
 			gopcode(OFUNC, Z, Z, &nod);
 			regfree(&nod);
 		} else
 			gopcode(OFUNC, Z, Z, l);
-		gpcdata(PCDATA_ArgSize, -1);
 		if(REGARG >= 0)
 			if(o != reg[REGARG])
 				reg[REGARG]--;

src/cmd/5g/gg.h

@@ -109,7 +109,6 @@ void	split64(Node*, Node*, Node*);
 void	splitclean(void);
 Node*	ncon(uint32 i);
 void	gtrack(Sym*);
-void	gargsize(int32);
 
 /*
  * obj.c

src/cmd/5g/ggen.c

@@ -179,28 +179,12 @@ fixautoused(Prog* p)
 void
 ginscall(Node *f, int proc)
 {
-	int32 arg;
 	Prog *p;
 	Node n1, r, r1, con;
 
 	if(f->type != T)
 		setmaxarg(f->type);
 
-	arg = -1;
-	// Most functions have a fixed-size argument block, so traceback uses that during unwind.
-	// Not all, though: there are some variadic functions in package runtime,
-	// and for those we emit call-specific metadata recorded by caller.
-	// Reflect generates functions with variable argsize (see reflect.methodValueCall/makeFuncStub),
-	// so we do this for all indirect calls as well.
-	if(f->type != T && (f->sym == S || (f->sym != S && f->sym->pkg == runtimepkg) || proc == 1 || proc == 2)) {
-		arg = f->type->argwid;
-		if(proc == 1 || proc == 2)
-			arg += 3*widthptr;
-	}
-
-	if(arg != -1)
-		gargsize(arg);
-
 	switch(proc) {
 	default:
 		fatal("ginscall: bad proc %d", proc);
@@ -297,9 +281,6 @@ ginscall(Node *f, int proc)
 		}
 		break;
 	}
-	
-	if(arg != -1)
-		gargsize(-1);
 }
 
 /*

src/cmd/5g/gsubr.c

@@ -205,16 +205,6 @@ ggloblnod(Node *nam)
 		p->reg |= NOPTR;
 }
 
-void
-gargsize(int32 size)
-{
-	Node n1, n2;
-	
-	nodconst(&n1, types[TINT32], PCDATA_ArgSize);
-	nodconst(&n2, types[TINT32], size);
-	gins(APCDATA, &n1, &n2);
-}
-
 void
 ggloblsym(Sym *s, int32 width, int8 flags)
 {

src/cmd/6c/cgen.c

@@ -945,7 +945,6 @@ cgen(Node *n, Node *nn)
 			return;
 		}
 		gargs(r, &nod, &nod1);
-		gpcdata(PCDATA_ArgSize, curarg);
 		if(l->addable < INDEXED) {
 			reglcgen(&nod, l, nn);
 			nod.op = OREGISTER;
@@ -953,12 +952,9 @@ cgen(Node *n, Node *nn)
 			regfree(&nod);
 		} else
 			gopcode(OFUNC, n->type, Z, l);
-		gpcdata(PCDATA_ArgSize, -1);
 		if(REGARG >= 0 && reg[REGARG])
 			reg[REGARG]--;
 		regret(&nod, n, l->type, 1); // update maxarg if nothing else
-		gpcdata(PCDATA_ArgSize, curarg);
-		gpcdata(PCDATA_ArgSize, -1);
 		if(nn != Z)
 			gmove(&nod, nn);
 		if(nod.op == OREGISTER)

src/cmd/6g/gg.h

@@ -99,7 +99,6 @@ int	sudoaddable(int, Node*, Addr*);
 void	afunclit(Addr*, Node*);
 void	nodfconst(Node*, Type*, Mpflt*);
 void	gtrack(Sym*);
-void	gargsize(vlong);
 void	fixlargeoffset(Node *n);
 
 /*

src/cmd/6g/ggen.c

@@ -175,7 +175,6 @@ fixautoused(Prog *p)
 void
 ginscall(Node *f, int proc)
 {
-	int32 arg;
 	Prog *p;
 	Node reg, con;
 	Node r1;
@@ -183,21 +182,6 @@ ginscall(Node *f, int proc)
 	if(f->type != T)
 		setmaxarg(f->type);
 
-	arg = -1;
-	// Most functions have a fixed-size argument block, so traceback uses that during unwind.
-	// Not all, though: there are some variadic functions in package runtime,
-	// and for those we emit call-specific metadata recorded by caller.
-	// Reflect generates functions with variable argsize (see reflect.methodValueCall/makeFuncStub),
-	// so we do this for all indirect calls as well.
-	if(f->type != T && (f->sym == S || (f->sym != S && f->sym->pkg == runtimepkg) || proc == 1 || proc == 2)) {
-		arg = f->type->argwid;
-		if(proc == 1 || proc == 2)
-			arg += 2*widthptr;
-	}
-
-	if(arg != -1)
-		gargsize(arg);
-
 	switch(proc) {
 	default:
 		fatal("ginscall: bad proc %d", proc);
@@ -275,9 +259,6 @@ ginscall(Node *f, int proc)
 		}
 		break;
 	}
-
-	if(arg != -1)
-		gargsize(-1);
 }
 
 /*

src/cmd/6g/gsubr.c

@@ -214,16 +214,6 @@ gtrack(Sym *s)
 	p->from.sym = linksym(s);
 }
 
-void
-gargsize(vlong size)
-{
-	Node n1, n2;
-	
-	nodconst(&n1, types[TINT32], PCDATA_ArgSize);
-	nodconst(&n2, types[TINT32], size);
-	gins(APCDATA, &n1, &n2);
-}
-
 void
 ggloblsym(Sym *s, int32 width, int8 flags)
 {

src/cmd/8c/cgen.c

@@ -938,7 +938,6 @@ cgen(Node *n, Node *nn)
 			return;
 		}
 		gargs(r, &nod, &nod1);
-		gpcdata(PCDATA_ArgSize, curarg);
 		if(l->addable < INDEXED) {
 			reglcgen(&nod, l, nn);
 			nod.op = OREGISTER;
@@ -946,7 +945,6 @@ cgen(Node *n, Node *nn)
 			regfree(&nod);
 		} else
 			gopcode(OFUNC, n->type, Z, l);
-		gpcdata(PCDATA_ArgSize, -1);
 		if(REGARG >= 0 && reg[REGARG])
 			reg[REGARG]--;
 		regret(&nod, n, l->type, 1); // update maxarg if nothing else

src/cmd/8g/gg.h

@@ -114,7 +114,6 @@ void	split64(Node*, Node*, Node*);
 void	splitclean(void);
 void	nswap(Node*, Node*);
 void	gtrack(Sym*);
-void	gargsize(int32);
 /*
  * cplx.c
  */

src/cmd/8g/ggen.c

@@ -217,21 +217,6 @@ ginscall(Node *f, int proc)
 	if(f->type != T)
 		setmaxarg(f->type);
 
-	arg = -1;
-	// Most functions have a fixed-size argument block, so traceback uses that during unwind.
-	// Not all, though: there are some variadic functions in package runtime,
-	// and for those we emit call-specific metadata recorded by caller.
-	// Reflect generates functions with variable argsize (see reflect.methodValueCall/makeFuncStub),
-	// so we do this for all indirect calls as well.
-	if(f->type != T && (f->sym == S || (f->sym != S && f->sym->pkg == runtimepkg) || proc == 1 || proc == 2)) {
-		arg = f->type->argwid;
-		if(proc == 1 || proc == 2)
-			arg += 2*widthptr;
-	}
-
-	if(arg != -1)
-		gargsize(arg);
-
 	switch(proc) {
 	default:
 		fatal("ginscall: bad proc %d", proc);
@@ -293,9 +278,6 @@ ginscall(Node *f, int proc)
 		}
 		break;
 	}
-	
-	if(arg != -1)
-		gargsize(-1);
 }
 
 /*

src/cmd/8g/gsubr.c

@@ -205,16 +205,6 @@ ggloblnod(Node *nam)
 		p->from.scale |= NOPTR;
 }
 
-void
-gargsize(int32 size)
-{
-	Node n1, n2;
-	
-	nodconst(&n1, types[TINT32], PCDATA_ArgSize);
-	nodconst(&n2, types[TINT32], size);
-	gins(APCDATA, &n1, &n2);
-}
-
 void
 ggloblsym(Sym *s, int32 width, int8 flags)
 {

src/runtime/funcdata.h

@@ -9,18 +9,12 @@
 //
 // symtab.go also contains a copy of these constants.
 
-// TODO(rsc): Remove PCDATA_ArgSize, renumber StackMapIndex to 0.
-#define PCDATA_ArgSize 0 /* argument size at CALL instruction */
-#define PCDATA_StackMapIndex 1
+#define PCDATA_StackMapIndex 0
 
 #define FUNCDATA_ArgsPointerMaps 0 /* garbage collector blocks */
 #define FUNCDATA_LocalsPointerMaps 1
 #define FUNCDATA_DeadValueMaps 2
 
-// TODO(rsc): Remove ARGSIZE.
-// To be used in assembly.
-#define ARGSIZE(n) PCDATA $PCDATA_ArgSize, $n
-
 // Pseudo-assembly statements.
 
 // GO_ARGS, GO_RESULTS_INITIALIZED, and NO_LOCAL_POINTERS are macros