cmd/gc: bypass DATA instruction for data initialized to integer constant

Eventually we will want to bypass DATA for everything,
but the relocations are not standardized well enough across
architectures to make that possible.

This did not help as much as I expected, but it is definitely better.
It shaves maybe 1-2% off all.bash depending on how much you
trust the timings of a single run:

Before: 241.139r 362.702u 112.967s
After:  234.339r 359.623u 111.045s

R=golang-codereviews, gobot, r, iant
CC=golang-codereviews
https://golang.org/cl/44650043

src/cmd/5g/gobj.c

@@ -223,27 +223,6 @@ dgostringptr(Sym *s, int off, char *str)
 	return dgostrlitptr(s, off, lit);
 }
 
-int
-duintxx(Sym *s, int off, uint64 v, int wid)
-{
-	Prog *p;
-
-	off = rnd(off, wid);
-
-	p = gins(ADATA, N, N);
-	p->from.type = D_OREG;
-	p->from.name = D_EXTERN;
-	p->from.sym = linksym(s);
-	p->from.offset = off;
-	p->reg = wid;
-	p->to.type = D_CONST;
-	p->to.name = D_NONE;
-	p->to.offset = v;
-	off += wid;
-
-	return off;
-}
-
 int
 dsymptr(Sym *s, int off, Sym *x, int xoff)
 {

src/cmd/6g/gobj.c

@@ -205,27 +205,6 @@ dgostringptr(Sym *s, int off, char *str)
 	return dgostrlitptr(s, off, lit);
 }
 
-int
-duintxx(Sym *s, int off, uint64 v, int wid)
-{
-	Prog *p;
-
-	off = rnd(off, wid);
-
-	p = gins(ADATA, N, N);
-	p->from.type = D_EXTERN;
-	p->from.index = D_NONE;
-	p->from.sym = linksym(s);
-	p->from.offset = off;
-	p->from.scale = wid;
-	p->to.type = D_CONST;
-	p->to.index = D_NONE;
-	p->to.offset = v;
-	off += wid;
-
-	return off;
-}
-
 int
 dsymptr(Sym *s, int off, Sym *x, int xoff)
 {

src/cmd/8g/gobj.c

@@ -216,28 +216,6 @@ dgostringptr(Sym *s, int off, char *str)
 	return dgostrlitptr(s, off, lit);
 }
 
-
-int
-duintxx(Sym *s, int off, uint64 v, int wid)
-{
-	Prog *p;
-
-	off = rnd(off, wid);
-
-	p = gins(ADATA, N, N);
-	p->from.type = D_EXTERN;
-	p->from.index = D_NONE;
-	p->from.sym = linksym(s);
-	p->from.offset = off;
-	p->from.scale = wid;
-	p->to.type = D_CONST;
-	p->to.index = D_NONE;
-	p->to.offset = v;
-	off += wid;
-
-	return off;
-}
-
 int
 dsymptr(Sym *s, int off, Sym *x, int xoff)
 {

src/cmd/gc/obj.c

@@ -160,6 +160,16 @@ linksym(Sym *s)
 	return s->lsym;	
 }
 
+int
+duintxx(Sym *s, int off, uint64 v, int wid)
+{
+	// Update symbol data directly instead of generating a
+	// DATA instruction that liblink will have to interpret later.
+	// This reduces compilation time and memory usage.
+	off = rnd(off, wid);
+	return setuintxx(ctxt, linksym(s), off, v, wid);
+}
+
 int
 duint8(Sym *s, int off, uint8 v)
 {