ref: 4343d4491f8251b0af5065d3898a2dc7cf8abf2f
parent: 198b6ea63a13382db039b8cf21a5b4798d62c659
author: Roberto E. Vargas Caballero <[email protected]>
date: Sat Sep 5 15:54:51 EDT 2015
Add more identities for logic operators
--- a/cc1/fold.c
+++ b/cc1/fold.c
@@ -376,42 +376,51 @@
return v;
}
-/*
- * 0 || i => i
- * 1 || i => 1
- * 0 && i => 0
- * 1 && i => i
- * i >> 0 => i
- * i << 0 => i
- * i + 0 => i
- * i - 0 => i
- * i | 0 => i
- * i ^ 0 => i
- * i * 0 => i,0
- * i * 1 => i
- * i / 1 => i
- * i & ~0 => i
- * i % 1 => i,1
- */
static Node *
identity(int *op, Node *lp, Node *rp)
{- int iszero, isone, istrue, val;
+ int iszeror, isoner, istruer, val;
+ int iszerol, isonel, istruel;
if (!rp)
return NULL;
- iszero = cmpnode(rp, 0);
- isone = cmpnode(rp, 1),
- istrue = !iszero && rp->constant;
+ iszeror = cmpnode(rp, 0);
+ isoner = cmpnode(rp, 1),
+ istruer = !iszeror && rp->constant;
+ iszerol = cmpnode(lp, 0);
+ isonel = cmpnode(lp, 1),
+ istruel = !iszerol && lp->constant;
switch (*op) {case OOR:
- val = 1;
- goto logic_operator;
+ /*
+ * 1 || i => 1 (free right)
+ * i || 0 => i (free right)
+ * 0 || i => i (free left)
+ * i || 1 => i,1 (comma)
+ */
+ if (isonel | iszeror)
+ goto free_right;
+ if (iszerol)
+ goto free_left;
+ if (isoner)
+ goto change_to_comma;
+ return NULL;
case OAND:
- val = 0;
- goto logic_operator;
+ /*
+ * 0 && i => 0 (free right)
+ * i && 1 => i (free right)
+ * 1 && i => i (free left)
+ * i && 0 => i,0 (comma)
+ */
+ if (iszerol | isoner)
+ goto free_right;
+ if (isonel)
+ goto free_left;
+ if (iszeror)
+ goto change_to_comma;
+ return NULL;
case OSHL:
case OSHR:
case OBXOR:
@@ -418,40 +427,52 @@
case OADD:
case OBOR:
case OSUB:
- if (iszero)
+ /*
+ * i >> 0 => i
+ * i << 0 => i
+ * i + 0 => i
+ * i - 0 => i
+ * i | 0 => i
+ * i ^ 0 => i
+ */
+ if (iszeror)
goto free_right;
return NULL;
case OMUL:
- if (iszero)
+ /*
+ * i * 0 => i,0
+ * i * 1 => i
+ */
+ if (iszeror)
goto change_to_comma;
+ if (isoner)
+ goto free_right;
+ return NULL;
case ODIV:
- if (isone)
+ /* i / 1 => i */
+ if (isoner)
goto free_right;
return NULL;
case OBAND:
+ /* i & ~0 => i */
if (cmpnode(rp, ones(lp->type->size * 8)))
goto free_right;
return NULL;
case OMOD:
- if (isone)
+ /* i % 1 => i,1 */
+ if (isoner)
goto change_to_comma;
default:
return NULL;
}
-logic_operator:
- if (!lp->constant)
- return NULL;
- if (cmpnode(lp, val))
- goto free_right;
+free_right:
+ freetree(rp);
+ return lp;
free_left:
freetree(lp);
return rp;
-
-free_right:
- freetree(rp);
- return lp;
change_to_comma:
*op = OCOMMA;