* src/SDCCpeeph.c (replaceRule): support empty replacement peephole

[fw/sdcc] / src / SDCCopt.c

diff --git a/src/SDCCopt.c b/src/SDCCopt.c
index cfb416d92d94f93501404ec6cb7c01f54276f4b8..4e9c2a7be560647efde1841a42b6a0a9efcf780c 100644 (file)
--- a/src/SDCCopt.c
+++ b/src/SDCCopt.c
@@ -770,6 +770,51 @@ replaceRegEqv (eBBlock ** ebbs, int count)
     }
 }
 
+/*-----------------------------------------------------------------*/
+/* findReqv - search for a register equivalent                     */
+/*-----------------------------------------------------------------*/
+operand *
+findReqv (symbol * prereqv, eBBlock ** ebbs, int count)
+{
+  int i;
+  iCode * ic;
+  
+  /* for all blocks do */
+  for (i=0; i<count; i++)
+    {
+      /* for all instructions in the block do */
+      for (ic = ebbs[i]->sch; ic; ic = ic->next)
+       {
+         if (ic->op == IFX)
+           {
+             if (IS_ITEMP (IC_COND (ic))
+                 && OP_SYMBOL (IC_COND (ic))->prereqv == prereqv)
+               return IC_COND (ic);
+           }
+         else if (ic->op == JUMPTABLE)
+           {
+             if (IS_ITEMP (IC_JTCOND (ic))
+                 && OP_SYMBOL (IC_JTCOND (ic))->prereqv == prereqv)
+               return IC_JTCOND (ic);
+           }
+         else
+           {
+             if (IS_ITEMP (IC_LEFT (ic))
+                 && OP_SYMBOL (IC_LEFT (ic))->prereqv == prereqv)
+               return IC_LEFT (ic);
+             if (IS_ITEMP (IC_RIGHT (ic))
+                 && OP_SYMBOL (IC_RIGHT (ic))->prereqv == prereqv)
+               return IC_RIGHT (ic);
+             if (IS_ITEMP (IC_RESULT (ic))
+                 && OP_SYMBOL (IC_RESULT (ic))->prereqv == prereqv)
+               return IC_RESULT (ic);
+           }
+       }
+    }
+  
+  return NULL;
+}
+
 /*-----------------------------------------------------------------*/
 /* killDeadCode - eliminates dead assignments                      */
 /*-----------------------------------------------------------------*/
@@ -903,6 +948,29 @@ killDeadCode (eBBlock ** ebbs, int count)
                  /* and defset of the block */
                  bitVectUnSetBit (ebbs[i]->defSet, ic->key);
 
+                 /* If this is the last of a register equivalent, */
+                 /* look for a successor register equivalent. */
+                 bitVectUnSetBit (OP_DEFS (IC_RESULT (ic)), ic->key);
+                 if (IS_ITEMP (IC_RESULT (ic))
+                     && OP_SYMBOL (IC_RESULT (ic))->isreqv
+                     && bitVectIsZero (OP_DEFS (IC_RESULT (ic))))
+                   {
+                     symbol * resultsym = OP_SYMBOL (IC_RESULT (ic));
+                     symbol * prereqv = resultsym->prereqv;
+                     
+                     if (OP_SYMBOL (prereqv->reqv) == resultsym)
+                       {
+                         operand * newreqv;
+
+                         IC_RESULT (ic) = NULL;
+                         newreqv = findReqv (prereqv, ebbs, count);
+                         if (newreqv)
+                           {
+                             prereqv->reqv = newreqv;
+                           }
+                       }
+                   }
+
                  /* delete the result */
                  IC_RESULT (ic) = NULL;