Patch for misleading comment in src/share/vm/opto/node.cpp

[Peter B. Kessler]

This comment is so wrong as almost to qualify as malicious.  Here's a patch that might help.

      src/share/vm/opto/node.cpp

      971 // If you modify the 'this' pointer's inputs, you must use 'set_req' with
      972 // def-use info.  If you are making a new Node (either as the new root or
      973 // some new internal piece) you must NOT use set_req with def-use info.
      974 // You can make a new Node with either 'new' or 'clone'.  In either case,
      975 // def-use info is (correctly) not generated.
      976 // Example: reshape "(X+3)+4" into "X+7":
      977 //    set_req(1,in(1)->in(1) /* grab X */, du /* must use DU on 'this' */);
      978 //    set_req(2,phase->intcon(7),du);
      979 //    return this;
 -    980 // Example: reshape "X*4" into "X<<1"
 -    981 //    return new (C,3) LShiftINode( in(1), phase->intcon(1) );
 +    980 // Example: reshape "X*4" into "X<<2"
 +    981 //    return new (C,3) LShiftINode( in(1), phase->intcon(2) );
      982 //
      983 // You must call 'phase->transform(X)' on any new Nodes X you make, except
 -    984 // for the returned root node.  Example: reshape "X*31" with "(X<<5)-1".
 -    985 //    Node *shift=phase->transform(new(C,3)LShiftINode(in(1),phase->intcon(5)));
 -    986 //    return new (C,3) AddINode(shift, phase->intcon(-1));
 +    984 // for the returned root node.  Example: reshape "X*31" with "(X<<5)-X".
 +    985 //    Node *shift=phase->transform(new(C,3)LShiftINode(in(1),phase->intcon(5)));
 +    986 //    return new (C,3) SubINode(shift, phase->intcon(in(1)));

The code *does* implement the transforms shown, but the transforms themselves are so wrong that it doesn't give me warm fuzzy feelings about trusting the author of this comment to transform my code.  (And I have some worries about overflows and sign bits on the last transform, but I haven't checked them out.)

			... peter