gsroa: allow anything that fits in a slice to be a slice

src/dmd/backend/gsroa.d

@@ -90,7 +90,8 @@ extern (D) private void sliceStructs_Gather(const symtab_t* symtab, SymInfo[] si
                                 ty = TYnptr;
                         }
                         sia[si].accessSlice = true;
-                        sia[si].ty[n] = tybasic(e.Ety);
+                        if (sz == SLICESIZE)
+                            sia[si].ty[n] = tybasic(e.Ety);
                     }
                     else
                     {
@@ -214,7 +215,7 @@ extern (D) private void sliceStructs_Replace(symtab_t* symtab, const SymInfo[] s
                     else // the nth slice
                     {
                         e.EV.Vsym = symtab.tab[sia[si].si0 + n];
-                        e.EV.Voffset = 0;
+                        e.EV.Voffset -= n * SLICESIZE;
                         //printf("replaced with:\n");
                         //elem_print(e);
                     }
@@ -269,6 +270,7 @@ void sliceStructs(symtab_t* symtab, block* startblock)
         //printf("slice1: %s\n", s.Sident.ptr);
 
         if (!(s.Sflags & SFLunambig))   // if somebody took the address of s
+        //if ((s.Sflags & (GTregcand | SFLunambig)) != (GTregcand | SFLunambig))
         {
             sia[si].canSlice = false;
             continue;
@@ -409,13 +411,17 @@ enum NOTSLICE = -1;
 int nthSlice(const(elem)* e)
 {
     const sz = tysize(e.Ety);
-    if (sz == SLICESIZE)
-    {
-        if (e.EV.Voffset == 0)
-            return 0;
-        if (e.EV.Voffset == SLICESIZE)
-            return 1;
-    }
+    const sliceSize = SLICESIZE;
+
+    /* See if e fits in a slice
+     */
+    const lwr = e.EV.Voffset;
+    const upr = lwr + sz;
+    if (0 <= lwr && upr <= sliceSize)
+        return 0;
+    if (sliceSize <= lwr && upr <= sliceSize * 2)
+        return 1;
+
     return NOTSLICE;
 }