Bootstrap miscomparison on mainline with checking disabled

[law@redhat.com]

In message < D48AC4D4-A9B3-11D8-A4A1-000393A6D2F2@physics.uc.edu >, Andrew Pinski
 writes:
 >
 >On May 19, 2004, at 12:35, law@redhat.com wrote:
 >
 >> In message < 1084983955.3630.262.camel@localhost.localdomain >, Diego 
 >> Novillo wri
 >> tes:
 >>> On Wed, 2004-05-19 at 12:08, law@redhat.com wrote:
 >>>
 >>>> It is the phiopt changes.  I've got a handle on it.
 >>>> jeff
 >>>>
 >>> Thanks.  I wonder if they may be also related to the number of
 >>> regressions we got on ppc.  The --enable-checking bootstrap on
 >>> powerpc-unknown-linux-gnu worked fine, but we are getting these
 >>> regressions.
 >>>
 >>> I don't think these regressions are due to the phiopt changes, though.
 >>> Most of the new failures are link errors for symbols not found.  Like
 >>> gcc.c-torture/execute/20001130-1.c
 >> It's possible if the stage1 compiler mis-compiled the stage2 compiler 
 >> in
 >> a fun an interesting way.
 >>
 >> I've got a fix going through testing now.
 >
 >I also have a fix, it looks like the following, does yours looks the 
 >same also?
 >Index: tree-ssa-phiopt.c
 >===================================================================
 >RCS file: /cvs/gcc/gcc/gcc/tree-ssa-phiopt.c,v
 >retrieving revision 2.6
 >diff -u -p -r2.6 tree-ssa-phiopt.c
 >--- tree-ssa-phiopt.c	19 May 2004 03:35:10 -0000	2.6
 >+++ tree-ssa-phiopt.c	19 May 2004 16:37:43 -0000
 >@@ -461,11 +461,12 @@ value_replacement (basic_block bb, tree
 >        || (operand_equal_p (arg1, TREE_OPERAND (cond, 0), 0)
 >  	  && operand_equal_p (arg0, TREE_OPERAND (cond, 1), 0)))
 >      {
 >-      edge e;
 >+      edge e, e1;
 >        tree arg;
 >
 >        e = (TREE_CODE (cond) == NE_EXPR ? true_edge : false_edge);
 >-      if (PHI_ARG_EDGE (phi, 0) == e)
 >+      e1 = (TREE_CODE (cond) == NE_EXPR ? false_edge : true_edge);
 >+      if (PHI_ARG_EDGE (phi, 0) == e || PHI_ARG_EDGE (phi, 1) == e1)
 >  	arg = arg0;
 >        else
 >  	arg = arg1;
They're probably equivalent.  Mine looks at e->dest to see if it is 
other_block, and if it is, then it does e = e->dest->succ to ensure
that e is an edge incoming to BB. And (of course) it adds suitable comments
in that hunk of code.

It's something I was somewhat concerned about after working through the abs
changes yesterday and the new code is modeled after how the abs changes work.

jeff
since