cmd/gc: remove C subclassing trick from popt.c

It does not convert to Go well.

Being able to do this just once, instead of 4 times, was the primary
motivation for all the recent refactoring (not that it wasn't overdue).

Still bit-for-bit identical.

Change-Id: Ia01f17948441bf64fa78ec4226f0bb40af0bbaab
Reviewed-on: https://go-review.googlesource.com/3962Reviewed-by: Austin Clements <austin@google.com>

src/cmd/5g/peep.c

@@ -65,7 +65,7 @@ peep(Prog *firstp)
 	Prog *p;
 	int t;
 
-	g = flowstart(firstp, sizeof(Flow));
+	g = flowstart(firstp, 0);
 	if(g == nil)
 		return;
 	gactive = 0;

src/cmd/6g/peep.c

@@ -97,7 +97,7 @@ peep(Prog *firstp)
 	Prog *p, *p1;
 	int t;
 
-	g = flowstart(firstp, sizeof(Flow));
+	g = flowstart(firstp, 0);
 	if(g == nil)
 		return;
 	gactive = 0;

src/cmd/8g/peep.c

@@ -94,7 +94,7 @@ peep(Prog *firstp)
 	Prog *p, *p1;
 	int t;
 
-	g = flowstart(firstp, sizeof(Flow));
+	g = flowstart(firstp, 0);
 	if(g == nil)
 		return;
 	gactive = 0;

src/cmd/9g/peep.c

@@ -55,7 +55,7 @@ peep(Prog *firstp)
 	Prog *p, *p1;
 	int t;
 
-	g = flowstart(firstp, sizeof(Flow));
+	g = flowstart(firstp, 0);
 	if(g == nil)
 		return;
 	gactive = 0;

src/cmd/gc/go.h

@@ -1557,9 +1557,12 @@ struct Flow {
 	
 	int32	active;	// usable by client
 
+	int32	id;		// sequence number in flow graph
 	int32	rpo;		// reverse post ordering
 	uint16	loop;		// x5 for every loop
 	uchar	refset;		// diagnostic generated
+	
+	void*	data;	// for use by client
 };
 
 struct Graph

src/cmd/gc/popt.h

@@ -68,11 +68,8 @@ uint64 STORE(Reg*);
 // A Reg is a wrapper around a single Prog (one instruction) that holds
 // register optimization information while the optimizer runs.
 // r->prog is the instruction.
-// r->prog->opt points back to r.
 struct	Reg
 {
-	Flow	f;
-
 	Bits	set;  		// regopt variables written by this instruction.
 	Bits	use1; 		// regopt variables read by prog->from.
 	Bits	use2; 		// regopt variables read by prog->to.
@@ -109,7 +106,7 @@ struct	Reg
 // cost.
 struct	Rgn
 {
-	Reg*	enter;
+	Flow*	enter;
 	short	cost;
 	short	varno;
 	short	regno;
@@ -143,17 +140,7 @@ EXTERN	struct
 /*
  * reg.c
  */
-int	rcmp(const void*, const void*);
 void	regopt(Prog*);
-void	addmove(Reg*, int, int, int);
-Bits	mkvar(Reg*, Adr*);
-void	prop(Reg*, Bits, Bits);
-void	synch(Reg*, Bits);
-uint64	allreg(uint64, Rgn*);
-void	paint1(Reg*, int);
-uint64	paint2(Reg*, int, int);
-void	paint3(Reg*, int, uint64, int);
-void	addreg(Adr*, int);
 void	dumpone(Flow*, int);
 void	dumpit(char*, Flow*, int);