utah rcsid 1.14 87/05/03 21:29:03: Add code from VAX compiler for detecting

ridiculous comparisons between small variables and large constants.

SCCS-vsn: old/pcc/ccom.tahoe/local2.c 1.23

diff --git a/usr/src/old/pcc/ccom.tahoe/local2.c b/usr/src/old/pcc/ccom.tahoe/local2.c
index 382b2b0..3474fb7 100644 (file)
--- a/usr/src/old/pcc/ccom.tahoe/local2.c
+++ b/usr/src/old/pcc/ccom.tahoe/local2.c
@@ -1,5 +1,5 @@
 #ifndef lint
 #ifndef lint

-static char sccsid[] = "@(#)local2.c   1.22 (Berkeley) %G%";
+static char sccsid[] = "@(#)local2.c   1.23 (Berkeley) %G%";

 #endif
 
 # include "pass2.h"
 #endif
 
 # include "pass2.h"


@@ -1297,6 +1297,7 @@ optim2( p ) register NODE *p; {
 # define nncon(p)      ((p)->in.op == ICON && (p)->in.name[0] == 0)
        register int o, i;
        register NODE *l, *r;
 # define nncon(p)      ((p)->in.op == ICON && (p)->in.name[0] == 0)
        register int o, i;
        register NODE *l, *r;

+       int lower, upper, result;

 
        switch (o = p->in.op) {
 
 
        switch (o = p->in.op) {
 


@@ -1386,6 +1387,95 @@ optim2( p ) register NODE *p; {
                        }
                }
                return;
                        }
                }
                return;

+
+       case ULE:
+       case ULT:
+       case UGE:
+       case UGT:
+               o -= (UGE-GE);
+       case EQ:
+       case NE:
+       case LE:
+       case LT:
+       case GE:
+       case GT:
+               /*
+                * Optimize comparisons against constants which are
+                * out of the range of a variable's precision.
+                * This saves some labor out in the code table
+                * handling ridiculous comparisons...
+                */
+               r = p->in.right;
+               l = p->in.left;
+               if (r->in.op != ICON ||
+                   r->tn.name[0] != '\0' ||
+                   tlen(l) >= tlen(r))
+                       return;
+               switch (l->in.type) {
+               case CHAR:
+                       lower = -(1 << SZCHAR - 1);
+                       upper = (1 << SZCHAR - 1) - 1;
+                       break;
+               case UCHAR:
+                       lower = 0;
+                       upper = (1 << SZCHAR) - 1;
+                       break;
+               case SHORT:
+                       lower = -(1 << SZSHORT - 1);
+                       upper = (1 << SZSHORT - 1) - 1;
+                       break;
+               case USHORT:
+                       lower = 0;
+                       upper = (1 << SZSHORT) - 1;
+                       break;
+               default:
+                       cerror("unsupported OPLOG in optim2");
+               }
+               result = -1;
+               i = r->tn.lval;
+               switch (o) {
+               case EQ:
+               case NE:
+                       if (lower == 0 && (unsigned) i > upper)
+                               result = o == NE;
+                       else if (i < lower || i > upper)
+                               result = o == NE;
+                       break;
+               case LT:
+               case GE:
+                       if (lower == 0 && (unsigned) i > upper)
+                               result = o == LT;
+                       else if (i <= lower)
+                               result = o != LT;
+                       else if (i > upper)
+                               result = o == LT;
+                       break;
+               case LE:
+               case GT:
+                       if (lower == 0 && (unsigned) i >= upper)
+                               result = o == LE;
+                       else if (i < lower)
+                               result = o != LE;
+                       else if (i >= upper)
+                               result = o == LE;
+                       break;
+               }
+               if (result == -1)
+                       return;
+
+               if (tshape(l, SAREG|SNAME|SCON|SOREG|STARNM)) {
+                       l->in.op = FREE;
+                       ncopy(p, r);
+                       r->in.op = FREE;
+                       p->tn.type = INT;
+                       p->tn.lval = result;
+               } else {
+                       p->in.op = COMOP;
+                       p->in.type = INT;
+                       r->tn.type = INT;
+                       r->tn.lval = result;
+               }
+               return;

        }
 # endif
 }
        }
 # endif
 }