improvement in registerization

R=r
OCL=29317
CL=29317

diff --git a/src/cmd/6g/reg.c b/src/cmd/6g/reg.c
index 865d3a60fd30991f8a923460c7ad4b2b36d6c817..daad3f12504a464e0ac75bed6943aa5768476211 100644 (file)
--- a/src/cmd/6g/reg.c
+++ b/src/cmd/6g/reg.c
@@ -748,11 +748,40 @@ doregbits(int r)
        return b;
 }
 
+static int
+overlap(Var *v, int o2, int w2)
+{
+       int o1, w1, t1, t2, z;
+       Bits bit;
+
+       o1 = v->offset;
+       w1 = v->width;
+       t1 = o1+w1;
+       t2 = o2+w2;
+       if(!(t1 > o2 && t2 > o1))
+               return 0;
+
+       // set to max extent
+       if(o2 < o1)
+               v->offset = o2;
+       if(t1 > t2)
+               v->width = t1-v->offset;
+       else
+               v->width = t2-v->offset;
+
+       // and dont registerize
+       bit = blsh(v-var);
+       for(z=0; z<BITS; z++)
+               addrs.b[z] |= bit.b[z];
+
+       return 1;
+}
+
 Bits
 mkvar(Reg *r, Adr *a)
 {
        Var *v;
-       int i, t, n, et, z, w;
+       int i, t, n, et, z, w, flag;
        int32 o;
        Bits bit;
        Sym *s;
@@ -793,12 +822,26 @@ mkvar(Reg *r, Adr *a)
        o = a->offset;
        w = a->width;
        v = var;
+
+       flag = 0;
        for(i=0; i<nvar; i++) {
                if(s == v->sym)
-               if(n == v->name)
-                       goto out;
+               if(n == v->name) {
+                       // if it is the same, use it
+                       if(v->etype == et)
+                       if(v->width == w)
+                       if(v->offset == o)
+                               goto out;
+
+                       // if it overlaps, set max
+                       // width and dont registerize
+                       if(overlap(v, o, w))
+                               flag = 1;
+               }
                v++;
        }
+       if(flag)
+               goto none;
 
        switch(et) {
        case 0:
@@ -826,18 +869,9 @@ mkvar(Reg *r, Adr *a)
 
 out:
        bit = blsh(i);
-       if(n == D_EXTERN || n == D_STATIC)
-               for(z=0; z<BITS; z++)
-                       externs.b[z] |= bit.b[z];
-       if(n == D_PARAM)
-               for(z=0; z<BITS; z++)
-                       params.b[z] |= bit.b[z];
 
-       // this has horrible consequences -
-       // no structure elements are registerized,
-       // but i dont know how to be more specific
-       if(v->etype != et || v->width != w || v->offset != o) {
-               /* funny punning */
+       // funny punning
+       if(v->etype != et) {
                if(debug['R'])
                        print("pun et=%d/%d w=%d/%d o=%d/%d %D\n",
                                v->etype, et,
@@ -845,8 +879,16 @@ out:
                                v->offset, o, a);
                for(z=0; z<BITS; z++)
                        addrs.b[z] |= bit.b[z];
+               goto none;
        }
 
+       if(n == D_EXTERN || n == D_STATIC)
+               for(z=0; z<BITS; z++)
+                       externs.b[z] |= bit.b[z];
+       if(n == D_PARAM)
+               for(z=0; z<BITS; z++)
+                       params.b[z] |= bit.b[z];
+
        return bit;
 
 none: