RE: [PATCH 2/2]middle-end: Support recognition of three-way max/min.

[Richard Biener <rguenther@suse.de>]

On Tue, 5 Jul 2022, Tamar Christina wrote:

> > >  	}
> > > +      else if (EDGE_SUCC (bb1, 0)->dest == EDGE_SUCC (bb2, 0)->dest
> > > +	       && single_succ_p (bb1)
> > > +	       && single_succ_p (bb2)
> > > +	       && single_pred_p (bb1)
> > > +	       && single_pred_p (bb2)
> > > +	       && single_succ_p (EDGE_SUCC (bb1, 0)->dest))
> > 
> > please do the single_succ/pred checks below where appropriate, also what's
> > the last check about? 
> 
> Done.
> 
> > why does the merge block need a single successor?
> 
> I was using it to fix an ICE, but I realize that's not the right fix. I'm now checking
> If the BB is empty instead, in which case it's just a fall through edge so don't
> treat it as a diamond.
> 
> > 
> > > +	{
> > > +	  gimple_stmt_iterator it1 = gsi_start_nondebug_after_labels_bb
> > (bb1);
> > > +	  gimple_stmt_iterator it2 = gsi_start_nondebug_after_labels_bb
> > (bb2);
> > > +	  if (gsi_one_before_end_p (it1) && gsi_one_before_end_p (it2))
> > > +	    {
> > > +	      gimple *stmt1 = gsi_stmt (it1);
> > > +	      gimple *stmt2 = gsi_stmt (it2);
> > > +	      if (is_gimple_assign (stmt1) && is_gimple_assign (stmt2))
> > > +		{
> > > +		  enum tree_code code1 = gimple_assign_rhs_code (stmt1);
> > > +		  enum tree_code code2 = gimple_assign_rhs_code (stmt2);
> > > +		  diamond_minmax_p
> > > +		    = (code1 == MIN_EXPR || code1 == MAX_EXPR)
> > > +		      && (code2 == MIN_EXPR || code2 == MAX_EXPR);
> > > +		}
> > > +	    }
> > > +	}
> > 
> > I'd generalize this to general diamond detection, simply cutting off
> > *_replacement workers that do not handle diamonds and do appropriate
> > checks in minmax_replacement only.
> > 
> 
> Done.
> 
> > >        else
> > >  	continue;
> > >
> > > @@ -316,6 +340,13 @@ tree_ssa_phiopt_worker (bool do_store_elim,
> > bool do_hoist_loads, bool early_p)
> > >  	  if (!candorest)
> > >  	    continue;
> > >
> > > +	  /* Check that we're looking for nested phis.  */
> > > +	  if (phis == NULL && diamond_minmax_p)
> > > +	    {
> > > +	      phis = phi_nodes (EDGE_SUCC (bb2, 0)->dest);
> > > +	      e2 = EDGE_SUCC (bb2, 0);
> > > +	    }
> > > +
> > 
> > instead
> > 
> >           basic_block merge = diamond_p ? EDGE_SUCC (bb2, 0)->dest : bb2;
> >           gimple_seq phis = phi_nodes (merge);
> > 
> 
> Done. 
> 
> > 
> > >  	  phi = single_non_singleton_phi_for_edges (phis, e1, e2);
> > >  	  if (!phi)
> > >  	    continue;
> > > @@ -329,6 +360,7 @@ tree_ssa_phiopt_worker (bool do_store_elim, bool
> > > do_hoist_loads, bool early_p)
> > >
> > >  	  gphi *newphi;
> > >  	  if (single_pred_p (bb1)
> > > +	      && !diamond_minmax_p
> > >  	      && (newphi = factor_out_conditional_conversion (e1, e2, phi,
> > >  							      arg0, arg1,
> > >  							      cond_stmt)))
> > > @@ -343,20 +375,25 @@ tree_ssa_phiopt_worker (bool do_store_elim,
> > bool do_hoist_loads, bool early_p)
> > >  	    }
> > >
> > >  	  /* Do the replacement of conditional if it can be done.  */
> > > -	  if (!early_p && two_value_replacement (bb, bb1, e2, phi, arg0,
> > arg1))
> > > +	  if (!early_p
> > > +	      && !diamond_minmax_p
> > > +	      && two_value_replacement (bb, bb1, e2, phi, arg0, arg1))
> > >  	    cfgchanged = true;
> > > -	  else if (match_simplify_replacement (bb, bb1, e1, e2, phi,
> > > -					       arg0, arg1,
> > > -					       early_p))
> > > +	  else if (!diamond_minmax_p
> > > +		   && match_simplify_replacement (bb, bb1, e1, e2, phi,
> > > +						  arg0, arg1, early_p))
> > >  	    cfgchanged = true;
> > >  	  else if (!early_p
> > > +		   && !diamond_minmax_p
> > >  		   && single_pred_p (bb1)
> > >  		   && cond_removal_in_builtin_zero_pattern (bb, bb1, e1,
> > e2,
> > >  							    phi, arg0, arg1))
> > >  	    cfgchanged = true;
> > > -	  else if (minmax_replacement (bb, bb1, e1, e2, phi, arg0, arg1))
> > > +	  else if (minmax_replacement (bb, bb1, bb2, e1, e2, phi, arg0, arg1,
> > > +				       diamond_minmax_p))
> > >  	    cfgchanged = true;
> > >  	  else if (single_pred_p (bb1)
> > > +		   && !diamond_minmax_p
> > >  		   && spaceship_replacement (bb, bb1, e1, e2, phi, arg0,
> > arg1))
> > >  	    cfgchanged = true;
> > >  	}
> > > @@ -385,7 +422,7 @@ tree_ssa_phiopt_worker (bool do_store_elim, bool
> > > do_hoist_loads, bool early_p)
> > >
> > >  static void
> > >  replace_phi_edge_with_variable (basic_block cond_block,
> > > -				edge e, gphi *phi, tree new_tree)
> > > +				edge e, gphi *phi, tree new_tree, bool
> > delete_bb = true)
> > >  {
> > >    basic_block bb = gimple_bb (phi);
> > >    gimple_stmt_iterator gsi;
> > > @@ -428,7 +465,7 @@ replace_phi_edge_with_variable (basic_block
> > cond_block,
> > >      edge_to_remove = EDGE_SUCC (cond_block, 1);
> > >    else
> > >      edge_to_remove = EDGE_SUCC (cond_block, 0);
> > > -  if (EDGE_COUNT (edge_to_remove->dest->preds) == 1)
> > > +  if (EDGE_COUNT (edge_to_remove->dest->preds) == 1 && delete_bb)
> > 
> > why do you need this change?
> 
> When this function replaces the edge it doesn't seem to update the dominators.
> Since It's replacing the middle BB we then end up with an error
> 
> gcc/testsuite/gcc.dg/tree-ssa/minmax-14.c:17:1: error: dominator of 5 should be 4, not 2
> 
> during early verify. So instead, I replace the BB but defer its deletion until cleanup which
> removes it and updates the dominators. 

Hmm, for a diamond shouldn't you replace

  if (EDGE_SUCC (cond_block, 0)->dest == bb)
    edge_to_remove = EDGE_SUCC (cond_block, 1);
  else
    edge_to_remove = EDGE_SUCC (cond_block, 0);

with

  if (EDGE_SUCC (cond_block, 0)->dest == bb)
    edge_to_remove = EDGE_SUCC (cond_block, 1);
  else if (EDGE_SUCC (cond_block, 1)->dest == bb)
    edge_to_remove = EDGE_SUCC (cond_block, 0);

thus, the code expects to be left with a fallthru to the PHI block
which is expected to have the immediate dominator being
cond_block but with a diamond there's a (possibly empty) block
inbetween and dominators are wrong.

So I think you simply need to handle this properly (and then
fall through to the else).


> > 
> > Did you check whether the new case works when the merge block has more
> > than two incoming edges?
> >
> 
> Yes, added a new testcase for it.
> 
> > > +  else if (middle_bb != alt_middle_bb && threeway_p)
> > > +    {
> > > +      /* Recognize the following case:
> > > +
> > > +	 if (smaller < larger)
> > > +	   a = MIN (smaller, c);
> > > +	 else
> > > +	   b = MIN (larger, c);
> > > +	 x = PHI <a, b>
> > > +
> > > +	 This is equivalent to
> > > +
> > > +	 a = MIN (smaller, c);
> > > +	 x = MIN (larger, a);  */
> > > +
> > > +      gimple *assign = last_and_only_stmt (middle_bb);
> > > +      tree lhs, op0, op1, bound;
> > > +      tree alt_lhs, alt_op0, alt_op1;
> > > +      bool invert = false;
> > > +
> > > +      if (!single_pred_p (middle_bb)
> > > +	  || !single_pred_p (alt_middle_bb))
> > > +	return false;
> > > +
> > > +      if (!assign
> > > +	  || gimple_code (assign) != GIMPLE_ASSIGN)
> > > +	return false;
> > > +
> > > +      lhs = gimple_assign_lhs (assign);
> > > +      ass_code = gimple_assign_rhs_code (assign);
> > > +      if (ass_code != MAX_EXPR && ass_code != MIN_EXPR)
> > > +	return false;
> > > +
> > > +      op0 = gimple_assign_rhs1 (assign);
> > > +      op1 = gimple_assign_rhs2 (assign);
> > > +
> > > +      assign = last_and_only_stmt (alt_middle_bb);
> > > +      if (!assign
> > > +	  || gimple_code (assign) != GIMPLE_ASSIGN)
> > > +	return false;
> > > +
> > > +      alt_lhs = gimple_assign_lhs (assign);
> > > +      if (ass_code != gimple_assign_rhs_code (assign))
> > > +	return false;
> > > +
> > > +      alt_op0 = gimple_assign_rhs1 (assign);
> > > +      alt_op1 = gimple_assign_rhs2 (assign);
> > > +
> > > +      if (!operand_equal_for_phi_arg_p (lhs, arg_true)
> > > +	 || !operand_equal_for_phi_arg_p (alt_lhs, arg_false))
> > > +	return false;
> > > +
> > > +      if ((operand_equal_for_phi_arg_p (op0, smaller)
> > > +		|| (alt_smaller
> > > +		    && operand_equal_for_phi_arg_p (op0, alt_smaller)))
> > > +	       && (operand_equal_for_phi_arg_p (alt_op0, larger)
> > > +		   || (alt_larger
> > > +		       && operand_equal_for_phi_arg_p (alt_op0, alt_larger))))
> > > +	{
> > > +	  /* We got here if the condition is true, i.e., SMALLER < LARGER.  */
> > > +	  if (!operand_equal_for_phi_arg_p (op1, alt_op1))
> > > +	    return false;
> > > +
> > > +	  if ((arg0 = strip_bit_not (op0)) != NULL
> > > +	      && (arg1 = strip_bit_not (alt_op0)) != NULL
> > > +	      && (bound = strip_bit_not (op1)) != NULL)
> > > +	    {
> > > +	      minmax = MAX_EXPR;
> > > +	      ass_code = invert_minmax_code (ass_code);
> > > +	      invert = true;
> > > +	    }
> > > +	  else
> > > +	    {
> > > +	      bound = op1;
> > > +	      minmax = MIN_EXPR;
> > > +	      arg0 = op0;
> > > +	      arg1 = alt_op0;
> > > +	     }
> > > +	}
> > > +      else if ((operand_equal_for_phi_arg_p (op0, larger)
> > > +		|| (alt_larger
> > > +		    && operand_equal_for_phi_arg_p (op0, alt_larger)))
> > > +	       && (operand_equal_for_phi_arg_p (alt_op0, smaller)
> > > +		   || (alt_smaller
> > > +		       && operand_equal_for_phi_arg_p (alt_op0,
> > alt_smaller))))
> > > +	{
> > > +	  /* We got here if the condition is true, i.e., SMALLER > LARGER.  */
> > > +	  if (!operand_equal_for_phi_arg_p (op1, alt_op1))
> > > +	    return false;
> > > +
> > > +	  if ((arg0 = strip_bit_not (op0)) != NULL
> > > +	      && (arg1 = strip_bit_not (alt_op0)) != NULL
> > > +	      && (bound = strip_bit_not (op1)) != NULL)
> > > +	    {
> > > +	      minmax = MIN_EXPR;
> > > +	      ass_code = invert_minmax_code (ass_code);
> > > +	      invert = true;
> > > +	    }
> > > +	  else
> > > +	    {
> > > +	      bound = op1;
> > > +	      minmax = MAX_EXPR;
> > > +	      arg0 = op0;
> > > +	      arg1 = alt_op0;
> > > +	     }
> > > +	}
> > > +      else
> > > +	return false;
> > 
> > Did you check you have coverage for all cases above in your testcases?
> 
> I've added some more, should now have full coverage.

Great.

> > 
> > > +      /* Reset any range information from the basic block.  */
> > > +      reset_flow_sensitive_info_in_bb (cond_bb);
> > 
> > Huh.  You need to reset flow-sensitive info of the middle-bb stmt that
> > prevails only...
> > 
> > > +      /* Emit the statement to compute min/max.  */
> > > +      gimple_seq stmts = NULL;
> > > +      tree phi_result = PHI_RESULT (phi);
> > > +      result = gimple_build (&stmts, minmax, TREE_TYPE (phi_result), arg0,
> > bound);
> > > +      result = gimple_build (&stmts, ass_code, TREE_TYPE
> > > + (phi_result), result, arg1);
> > 
> > ... but you are re-building both here.  And also you drop locations, the
> > preserved min/max should keep the old, the new should get the location of
> > ... hmm, the condition possibly?
> 
> Done, also added a testcase which checks that it still works when -g.
> 
> Bootstrapped Regtested on aarch64-none-linux-gnu and no issues.
> 
> Ok for master?

Besides the above issue it looks good to me.

Thanks and sorry for the delay.
Richard.

> Thanks,
> Tamar
> 
> gcc/ChangeLog:
> 
> 	* tree-ssa-phiopt.cc (minmax_replacement): Optionally search for the phi
> 	sequence of a three-way conditional.
> 	(replace_phi_edge_with_variable): Support deferring of BB removal.
> 	(tree_ssa_phiopt_worker): Detect diamond phi structure for three-way
> 	min/max.
> 	(strip_bit_not, invert_minmax_code): New.
> 
> gcc/testsuite/ChangeLog:
> 
> 	* gcc.dg/tree-ssa/split-path-1.c: Disable phi-opts so we don't optimize
> 	code away.
> 	* gcc.dg/tree-ssa/minmax-10.c: New test.
> 	* gcc.dg/tree-ssa/minmax-11.c: New test.
> 	* gcc.dg/tree-ssa/minmax-12.c: New test.
> 	* gcc.dg/tree-ssa/minmax-13.c: New test.
> 	* gcc.dg/tree-ssa/minmax-14.c: New test.
> 	* gcc.dg/tree-ssa/minmax-15.c: New test.
> 	* gcc.dg/tree-ssa/minmax-16.c: New test.
> 	* gcc.dg/tree-ssa/minmax-3.c: New test.
> 	* gcc.dg/tree-ssa/minmax-4.c: New test.
> 	* gcc.dg/tree-ssa/minmax-5.c: New test.
> 	* gcc.dg/tree-ssa/minmax-6.c: New test.
> 	* gcc.dg/tree-ssa/minmax-7.c: New test.
> 	* gcc.dg/tree-ssa/minmax-8.c: New test.
> 	* gcc.dg/tree-ssa/minmax-9.c: New test.
> 
> --- inline copy of patch ---
> 
> diff --git a/gcc/testsuite/gcc.dg/tree-ssa/minmax-10.c b/gcc/testsuite/gcc.dg/tree-ssa/minmax-10.c
> new file mode 100644
> index 0000000000000000000000000000000000000000..589953684416a9d263084deb58f6cde7094dd517
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/tree-ssa/minmax-10.c
> @@ -0,0 +1,20 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O -fdump-tree-optimized" } */
> +
> +#include <stdint.h>
> +
> +uint8_t three_max (uint8_t xc, uint8_t xm, uint8_t xy) {
> +    uint8_t	 xk;
> +    xc=~xc;
> +    xm=~xm;
> +    xy=~xy;
> +    if (xc > xm) {
> +        xk = (uint8_t) (xc > xy ? xc : xy);
> +    } else {
> +        xk = (uint8_t) (xm > xy ? xm : xy);
> +    }
> +    return xk;
> +}
> +
> +/* { dg-final { scan-tree-dump-times "MIN_EXPR" 2 "optimized" } } */
> +/* { dg-final { scan-tree-dump-times "= ~" 1 "optimized" } } */
> diff --git a/gcc/testsuite/gcc.dg/tree-ssa/minmax-11.c b/gcc/testsuite/gcc.dg/tree-ssa/minmax-11.c
> new file mode 100644
> index 0000000000000000000000000000000000000000..1c2ef01b5d1e639fbf95bb5ca473b63cc98e9df1
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/tree-ssa/minmax-11.c
> @@ -0,0 +1,21 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O -fdump-tree-optimized" } */
> +
> +#include <stdint.h>
> +
> +uint8_t three_minmax1 (uint8_t xc, uint8_t xm, uint8_t xy) {
> +	uint8_t	 xk;
> +    xc=~xc;
> +    xm=~xm;
> +    xy=~xy;
> +    if (xc > xm) {
> +        xk = (uint8_t) (xc < xy ? xc : xy);
> +    } else {
> +        xk = (uint8_t) (xm < xy ? xm : xy);
> +    }
> +    return xk;
> +}
> +
> +/* { dg-final { scan-tree-dump-times "MIN_EXPR" 1 "optimized" } } */
> +/* { dg-final { scan-tree-dump-times "MAX_EXPR" 1 "optimized" } } */
> +/* { dg-final { scan-tree-dump-times "= ~" 1 "optimized" } } */
> diff --git a/gcc/testsuite/gcc.dg/tree-ssa/minmax-12.c b/gcc/testsuite/gcc.dg/tree-ssa/minmax-12.c
> new file mode 100644
> index 0000000000000000000000000000000000000000..3d0c07d9b57dd689bcb89653937727ab441e7f2b
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/tree-ssa/minmax-12.c
> @@ -0,0 +1,20 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O -fdump-tree-phiopt" } */
> +
> +#include <stdint.h>
> +
> +uint8_t three_minmax3 (uint8_t xc, uint8_t xm, uint8_t xy) {
> +        uint8_t  xk;
> +    xc=~xc;
> +    xm=~xm;
> +    xy=~xy;
> +    if (xc > xm) {
> +        xk = (uint8_t) (xy < xc ? xc : xy);
> +    } else {
> +        xk = (uint8_t) (xm < xy ? xm : xy);
> +    }
> +    return xk;
> +}
> +
> +/* { dg-final { scan-tree-dump-times "MIN_EXPR" 1 "phiopt1" } } */
> +/* { dg-final { scan-tree-dump-times "MAX_EXPR" 1 "phiopt1" } } */
> diff --git a/gcc/testsuite/gcc.dg/tree-ssa/minmax-13.c b/gcc/testsuite/gcc.dg/tree-ssa/minmax-13.c
> new file mode 100644
> index 0000000000000000000000000000000000000000..c0d0f27c8027ae87654532d1b919cfeccf4413e0
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/tree-ssa/minmax-13.c
> @@ -0,0 +1,19 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O -fdump-tree-phiopt" } */
> +
> +#include <stdint.h>
> +
> +uint8_t three_minmax2 (uint8_t xc, uint8_t xm, uint8_t xy) {
> +	uint8_t	 xk;
> +    xc=~xc;
> +    xm=~xm;
> +    xy=~xy;
> +    if (xc > xm) {
> +        xk = (uint8_t) (xc > xy ? xc : xy);
> +    } else {
> +        xk = (uint8_t) (xm < xy ? xm : xy);
> +    }
> +    return xk;
> +}
> +/* { dg-final { scan-tree-dump-times "MIN_EXPR" 1 "phiopt1" } } */
> +/* { dg-final { scan-tree-dump-times "MAX_EXPR" 1 "phiopt1" } } */
> diff --git a/gcc/testsuite/gcc.dg/tree-ssa/minmax-14.c b/gcc/testsuite/gcc.dg/tree-ssa/minmax-14.c
> new file mode 100644
> index 0000000000000000000000000000000000000000..9c0cadbf7e3119527cb2007d01fe4c7dd772c069
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/tree-ssa/minmax-14.c
> @@ -0,0 +1,21 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O -fdump-tree-optimized" } */
> +
> +#include <stdint.h>
> +
> +uint8_t three_minmax11 (uint8_t xc, uint8_t xm, uint8_t xy) {
> +        uint8_t  xk;
> +    xc=~xc;
> +    xm=~xm;
> +    xy=~xy;
> +    if (xc < xm) {
> +        xk = (uint8_t) (xc > xy ? xc : xy);
> +    } else {
> +        xk = (uint8_t) (xm > xy ? xm : xy);
> +    }
> +    return xk;
> +}
> +
> +/* { dg-final { scan-tree-dump-times "MIN_EXPR" 1 "optimized" } } */
> +/* { dg-final { scan-tree-dump-times "MAX_EXPR" 1 "optimized" } } */
> +/* { dg-final { scan-tree-dump-times "= ~" 1 "optimized" } } */
> diff --git a/gcc/testsuite/gcc.dg/tree-ssa/minmax-15.c b/gcc/testsuite/gcc.dg/tree-ssa/minmax-15.c
> new file mode 100644
> index 0000000000000000000000000000000000000000..1d97a16564f069b4348ff325c4fd713a224f838a
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/tree-ssa/minmax-15.c
> @@ -0,0 +1,21 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O -fdump-tree-phiopt" } */
> +
> +#include <stdint.h>
> +#include <stdbool.h>
> +
> +uint8_t three_min (uint8_t xc, uint8_t xm, uint8_t xy, bool m) {
> +    uint8_t  xk;
> +    if (xc)
> +      {
> +        if (xc < xm) {
> +            xk = (uint8_t) (xc < xy ? xc : xy);
> +        } else {
> +            xk = (uint8_t) (xm < xy ? xm : xy);
> +        }
> +      }
> +
> +    return xk;
> +}
> +/* { dg-final { scan-tree-dump-times "MIN_EXPR" 3 "phiopt1" } } */
> +/* { dg-final { scan-tree-dump-times "MAX_EXPR" 0 "phiopt1" } } */
> diff --git a/gcc/testsuite/gcc.dg/tree-ssa/minmax-16.c b/gcc/testsuite/gcc.dg/tree-ssa/minmax-16.c
> new file mode 100644
> index 0000000000000000000000000000000000000000..89377a2cb341bdafa6ba145c61c1f966af536839
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/tree-ssa/minmax-16.c
> @@ -0,0 +1,17 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O -fdump-tree-phiopt -g" } */
> +
> +#include <stdint.h>
> +
> +uint8_t three_min (uint8_t xc, uint8_t xm, uint8_t xy) {
> +	uint8_t	 xk;
> +    if (xc < xm) {
> +        xk = (uint8_t) (xc < xy ? xc : xy);
> +    } else {
> +        xk = (uint8_t) (xm < xy ? xm : xy);
> +    }
> +    return xk;
> +}
> +
> +/* { dg-final { scan-tree-dump-times "MIN_EXPR" 3 "phiopt1" } } */
> +/* { dg-final { scan-tree-dump-times "MAX_EXPR" 0 "phiopt1" } } */
> diff --git a/gcc/testsuite/gcc.dg/tree-ssa/minmax-3.c b/gcc/testsuite/gcc.dg/tree-ssa/minmax-3.c
> new file mode 100644
> index 0000000000000000000000000000000000000000..de3b2e946e81701e3b75f580e6a843695a05786e
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/tree-ssa/minmax-3.c
> @@ -0,0 +1,17 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O -fdump-tree-phiopt" } */
> +
> +#include <stdint.h>
> +
> +uint8_t three_min (uint8_t xc, uint8_t xm, uint8_t xy) {
> +	uint8_t	 xk;
> +    if (xc < xm) {
> +        xk = (uint8_t) (xc < xy ? xc : xy);
> +    } else {
> +        xk = (uint8_t) (xm < xy ? xm : xy);
> +    }
> +    return xk;
> +}
> +
> +/* { dg-final { scan-tree-dump-times "MIN_EXPR" 3 "phiopt1" } } */
> +/* { dg-final { scan-tree-dump-times "MAX_EXPR" 0 "phiopt1" } } */
> diff --git a/gcc/testsuite/gcc.dg/tree-ssa/minmax-4.c b/gcc/testsuite/gcc.dg/tree-ssa/minmax-4.c
> new file mode 100644
> index 0000000000000000000000000000000000000000..0b6d667be868c2405eaefd17cb522da44bafa0e2
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/tree-ssa/minmax-4.c
> @@ -0,0 +1,17 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O -fdump-tree-phiopt" } */
> +
> +#include <stdint.h>
> +
> +uint8_t three_max (uint8_t xc, uint8_t xm, uint8_t xy) {
> +    uint8_t	 xk;
> +    if (xc > xm) {
> +        xk = (uint8_t) (xc > xy ? xc : xy);
> +    } else {
> +        xk = (uint8_t) (xm > xy ? xm : xy);
> +    }
> +    return xk;
> +}
> +
> +/* { dg-final { scan-tree-dump-times "MIN_EXPR" 0 "phiopt1" } } */
> +/* { dg-final { scan-tree-dump-times "MAX_EXPR" 3 "phiopt1" } } */
> diff --git a/gcc/testsuite/gcc.dg/tree-ssa/minmax-5.c b/gcc/testsuite/gcc.dg/tree-ssa/minmax-5.c
> new file mode 100644
> index 0000000000000000000000000000000000000000..650601a3cc75d09a9e6e54a35f5b9993074f8510
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/tree-ssa/minmax-5.c
> @@ -0,0 +1,17 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O -fdump-tree-phiopt" } */
> +
> +#include <stdint.h>
> +
> +uint8_t three_minmax1 (uint8_t xc, uint8_t xm, uint8_t xy) {
> +	uint8_t	 xk;
> +    if (xc > xm) {
> +        xk = (uint8_t) (xc < xy ? xc : xy);
> +    } else {
> +        xk = (uint8_t) (xm < xy ? xm : xy);
> +    }
> +    return xk;
> +}
> +
> +/* { dg-final { scan-tree-dump-times "MIN_EXPR" 2 "phiopt1" } } */
> +/* { dg-final { scan-tree-dump-times "MAX_EXPR" 1 "phiopt1" } } */
> diff --git a/gcc/testsuite/gcc.dg/tree-ssa/minmax-6.c b/gcc/testsuite/gcc.dg/tree-ssa/minmax-6.c
> new file mode 100644
> index 0000000000000000000000000000000000000000..a628f6d99222958cfd8c410f0e85639e3a49dd4b
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/tree-ssa/minmax-6.c
> @@ -0,0 +1,17 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O -fdump-tree-phiopt" } */
> +
> +#include <stdint.h>
> +
> +uint8_t three_minmax3 (uint8_t xc, uint8_t xm, uint8_t xy) {
> +        uint8_t  xk;
> +    if (xc > xm) {
> +        xk = (uint8_t) (xy < xc ? xc : xy);
> +    } else {
> +        xk = (uint8_t) (xm < xy ? xm : xy);
> +    }
> +    return xk;
> +}
> +
> +/* { dg-final { scan-tree-dump-times "MIN_EXPR" 1 "phiopt1" } } */
> +/* { dg-final { scan-tree-dump-times "MAX_EXPR" 1 "phiopt1" } } */
> diff --git a/gcc/testsuite/gcc.dg/tree-ssa/minmax-7.c b/gcc/testsuite/gcc.dg/tree-ssa/minmax-7.c
> new file mode 100644
> index 0000000000000000000000000000000000000000..cb42412c4ada433b2f59df0a8bef9fa7b1c5e104
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/tree-ssa/minmax-7.c
> @@ -0,0 +1,16 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O -fdump-tree-phiopt" } */
> +
> +#include <stdint.h>
> +
> +uint8_t three_minmax2 (uint8_t xc, uint8_t xm, uint8_t xy) {
> +	uint8_t	 xk;
> +    if (xc > xm) {
> +        xk = (uint8_t) (xc > xy ? xc : xy);
> +    } else {
> +        xk = (uint8_t) (xm < xy ? xm : xy);
> +    }
> +    return xk;
> +}
> +/* { dg-final { scan-tree-dump-times "MIN_EXPR" 1 "phiopt1" } } */
> +/* { dg-final { scan-tree-dump-times "MAX_EXPR" 1 "phiopt1" } } */
> diff --git a/gcc/testsuite/gcc.dg/tree-ssa/minmax-8.c b/gcc/testsuite/gcc.dg/tree-ssa/minmax-8.c
> new file mode 100644
> index 0000000000000000000000000000000000000000..9cd050e932376bc50bd6ae60cb654fcab0bfdd1c
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/tree-ssa/minmax-8.c
> @@ -0,0 +1,17 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O -fdump-tree-phiopt" } */
> +
> +#include <stdint.h>
> +
> +uint8_t three_minmax11 (uint8_t xc, uint8_t xm, uint8_t xy) {
> +        uint8_t  xk;
> +    if (xc < xm) {
> +        xk = (uint8_t) (xc > xy ? xc : xy);
> +    } else {
> +        xk = (uint8_t) (xm > xy ? xm : xy);
> +    }
> +    return xk;
> +}
> +
> +/* { dg-final { scan-tree-dump-times "MIN_EXPR" 1 "phiopt1" } } */
> +/* { dg-final { scan-tree-dump-times "MAX_EXPR" 2 "phiopt1" } } */
> diff --git a/gcc/testsuite/gcc.dg/tree-ssa/minmax-9.c b/gcc/testsuite/gcc.dg/tree-ssa/minmax-9.c
> new file mode 100644
> index 0000000000000000000000000000000000000000..24f580271c3ac3945860b506d4dc7d178a826093
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/tree-ssa/minmax-9.c
> @@ -0,0 +1,20 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O -fdump-tree-optimized" } */
> +
> +#include <stdint.h>
> +
> +uint8_t three_min (uint8_t xc, uint8_t xm, uint8_t xy) {
> +	uint8_t	 xk;
> +    xc=~xc;
> +    xm=~xm;
> +    xy=~xy;
> +    if (xc < xm) {
> +        xk = (uint8_t) (xc < xy ? xc : xy);
> +    } else {
> +        xk = (uint8_t) (xm < xy ? xm : xy);
> +    }
> +    return xk;
> +}
> +
> +/* { dg-final { scan-tree-dump-times "= ~" 1 "optimized" } } */
> +/* { dg-final { scan-tree-dump-times "MAX_EXPR" 2 "optimized" } } */
> diff --git a/gcc/testsuite/gcc.dg/tree-ssa/split-path-1.c b/gcc/testsuite/gcc.dg/tree-ssa/split-path-1.c
> index 8b23ef4c7a3484cdc1647ee6d1b150f15685beff..902dde44a50e171b4f34ba7247d75a32d2c860ed 100644
> --- a/gcc/testsuite/gcc.dg/tree-ssa/split-path-1.c
> +++ b/gcc/testsuite/gcc.dg/tree-ssa/split-path-1.c
> @@ -1,5 +1,5 @@
>  /* { dg-do run } */
> -/* { dg-options "-O2 -fsplit-paths -fdump-tree-split-paths-details --param max-jump-thread-duplication-stmts=20" } */
> +/* { dg-options "-O2 -fsplit-paths -fdump-tree-split-paths-details --param max-jump-thread-duplication-stmts=20 -fno-ssa-phiopt" } */
>  
>  #include <stdio.h>
>  #include <stdlib.h>
> diff --git a/gcc/tree-ssa-phiopt.cc b/gcc/tree-ssa-phiopt.cc
> index e61d9736937573d773acdf3e43a7c76074bfb2c7..df543b22cd720538c14bcea72fc78a8dec9bf12b 100644
> --- a/gcc/tree-ssa-phiopt.cc
> +++ b/gcc/tree-ssa-phiopt.cc
> @@ -63,8 +63,8 @@ static gphi *factor_out_conditional_conversion (edge, edge, gphi *, tree, tree,
>  						gimple *);
>  static int value_replacement (basic_block, basic_block,
>  			      edge, edge, gphi *, tree, tree);
> -static bool minmax_replacement (basic_block, basic_block,
> -				edge, edge, gphi *, tree, tree);
> +static bool minmax_replacement (basic_block, basic_block, basic_block,
> +				edge, edge, gphi *, tree, tree, bool);
>  static bool spaceship_replacement (basic_block, basic_block,
>  				   edge, edge, gphi *, tree, tree);
>  static bool cond_removal_in_builtin_zero_pattern (basic_block, basic_block,
> @@ -74,7 +74,7 @@ static bool cond_store_replacement (basic_block, basic_block, edge, edge,
>  				    hash_set<tree> *);
>  static bool cond_if_else_store_replacement (basic_block, basic_block, basic_block);
>  static hash_set<tree> * get_non_trapping ();
> -static void replace_phi_edge_with_variable (basic_block, edge, gphi *, tree);
> +static void replace_phi_edge_with_variable (basic_block, edge, gphi *, tree, bool);
>  static void hoist_adjacent_loads (basic_block, basic_block,
>  				  basic_block, basic_block);
>  static bool gate_hoist_loads (void);
> @@ -200,6 +200,7 @@ tree_ssa_phiopt_worker (bool do_store_elim, bool do_hoist_loads, bool early_p)
>        basic_block bb1, bb2;
>        edge e1, e2;
>        tree arg0, arg1;
> +      bool diamond_p = false;
>  
>        bb = bb_order[i];
>  
> @@ -266,6 +267,9 @@ tree_ssa_phiopt_worker (bool do_store_elim, bool do_hoist_loads, bool early_p)
>  	    hoist_adjacent_loads (bb, bb1, bb2, bb3);
>  	  continue;
>  	}
> +      else if (EDGE_SUCC (bb1, 0)->dest == EDGE_SUCC (bb2, 0)->dest
> +	       && !empty_block_p (bb1))
> +	diamond_p = true;
>        else
>  	continue;
>  
> @@ -294,10 +298,13 @@ tree_ssa_phiopt_worker (bool do_store_elim, bool do_hoist_loads, bool early_p)
>  	}
>        else
>  	{
> -	  gimple_seq phis = phi_nodes (bb2);
>  	  gimple_stmt_iterator gsi;
>  	  bool candorest = true;
>  
> +	  /* Check that we're looking for nested phis.  */
> +	  basic_block merge = diamond_p ? EDGE_SUCC (bb2, 0)->dest : bb2;
> +	  gimple_seq phis = phi_nodes (merge);
> +
>  	  /* Value replacement can work with more than one PHI
>  	     so try that first. */
>  	  if (!early_p)
> @@ -317,6 +324,7 @@ tree_ssa_phiopt_worker (bool do_store_elim, bool do_hoist_loads, bool early_p)
>  	  if (!candorest)
>  	    continue;
>  
> +	  e2 = diamond_p ? EDGE_SUCC (bb2, 0) : e2;
>  	  phi = single_non_singleton_phi_for_edges (phis, e1, e2);
>  	  if (!phi)
>  	    continue;
> @@ -330,6 +338,7 @@ tree_ssa_phiopt_worker (bool do_store_elim, bool do_hoist_loads, bool early_p)
>  
>  	  gphi *newphi;
>  	  if (single_pred_p (bb1)
> +	      && !diamond_p
>  	      && (newphi = factor_out_conditional_conversion (e1, e2, phi,
>  							      arg0, arg1,
>  							      cond_stmt)))
> @@ -344,20 +353,25 @@ tree_ssa_phiopt_worker (bool do_store_elim, bool do_hoist_loads, bool early_p)
>  	    }
>  
>  	  /* Do the replacement of conditional if it can be done.  */
> -	  if (!early_p && two_value_replacement (bb, bb1, e2, phi, arg0, arg1))
> +	  if (!early_p
> +	      && !diamond_p
> +	      && two_value_replacement (bb, bb1, e2, phi, arg0, arg1))
>  	    cfgchanged = true;
> -	  else if (match_simplify_replacement (bb, bb1, e1, e2, phi,
> -					       arg0, arg1,
> -					       early_p))
> +	  else if (!diamond_p
> +		   && match_simplify_replacement (bb, bb1, e1, e2, phi,
> +						  arg0, arg1, early_p))
>  	    cfgchanged = true;
>  	  else if (!early_p
> +		   && !diamond_p
>  		   && single_pred_p (bb1)
>  		   && cond_removal_in_builtin_zero_pattern (bb, bb1, e1, e2,
>  							    phi, arg0, arg1))
>  	    cfgchanged = true;
> -	  else if (minmax_replacement (bb, bb1, e1, e2, phi, arg0, arg1))
> +	  else if (minmax_replacement (bb, bb1, bb2, e1, e2, phi, arg0, arg1,
> +				       diamond_p))
>  	    cfgchanged = true;
>  	  else if (single_pred_p (bb1)
> +		   && !diamond_p
>  		   && spaceship_replacement (bb, bb1, e1, e2, phi, arg0, arg1))
>  	    cfgchanged = true;
>  	}
> @@ -386,7 +400,7 @@ tree_ssa_phiopt_worker (bool do_store_elim, bool do_hoist_loads, bool early_p)
>  
>  static void
>  replace_phi_edge_with_variable (basic_block cond_block,
> -				edge e, gphi *phi, tree new_tree)
> +				edge e, gphi *phi, tree new_tree, bool delete_bb = true)
>  {
>    basic_block bb = gimple_bb (phi);
>    gimple_stmt_iterator gsi;
> @@ -427,7 +441,7 @@ replace_phi_edge_with_variable (basic_block cond_block,
>      edge_to_remove = EDGE_SUCC (cond_block, 1);
>    else
>      edge_to_remove = EDGE_SUCC (cond_block, 0);
> -  if (EDGE_COUNT (edge_to_remove->dest->preds) == 1)
> +  if (EDGE_COUNT (edge_to_remove->dest->preds) == 1 && delete_bb)
>      {
>        e->flags |= EDGE_FALLTHRU;
>        e->flags &= ~(EDGE_TRUE_VALUE | EDGE_FALSE_VALUE);
> @@ -1733,15 +1747,52 @@ value_replacement (basic_block cond_bb, basic_block middle_bb,
>    return 0;
>  }
>  
> +/* If VAR is an SSA_NAME that points to a BIT_NOT_EXPR then return the TREE for
> +   the value being inverted.  */
> +
> +static tree
> +strip_bit_not (tree var)
> +{
> +  if (TREE_CODE (var) != SSA_NAME)
> +    return NULL_TREE;
> +
> +  gimple *assign = SSA_NAME_DEF_STMT (var);
> +  if (gimple_code (assign) != GIMPLE_ASSIGN)
> +    return NULL_TREE;
> +
> +  if (gimple_assign_rhs_code (assign) != BIT_NOT_EXPR)
> +    return NULL_TREE;
> +
> +  return gimple_assign_rhs1 (assign);
> +}
> +
> +/* Invert a MIN to a MAX or a MAX to a MIN expression CODE.  */
> +
> +enum tree_code
> +invert_minmax_code (enum tree_code code)
> +{
> +  switch (code) {
> +  case MIN_EXPR:
> +    return MAX_EXPR;
> +  case MAX_EXPR:
> +    return MIN_EXPR;
> +  default:
> +    gcc_unreachable ();
> +  }
> +}
> +
>  /*  The function minmax_replacement does the main work of doing the minmax
>      replacement.  Return true if the replacement is done.  Otherwise return
>      false.
>      BB is the basic block where the replacement is going to be done on.  ARG0
> -    is argument 0 from the PHI.  Likewise for ARG1.  */
> +    is argument 0 from the PHI.  Likewise for ARG1.
> +
> +    If THREEWAY_P then expect the BB to be laid out in diamond shape with each
> +    BB containing only a MIN or MAX expression.  */
>  
>  static bool
> -minmax_replacement (basic_block cond_bb, basic_block middle_bb,
> -		    edge e0, edge e1, gphi *phi, tree arg0, tree arg1)
> +minmax_replacement (basic_block cond_bb, basic_block middle_bb, basic_block alt_middle_bb,
> +		    edge e0, edge e1, gphi *phi, tree arg0, tree arg1, bool threeway_p)
>  {
>    tree result;
>    edge true_edge, false_edge;
> @@ -1896,16 +1947,20 @@ minmax_replacement (basic_block cond_bb, basic_block middle_bb,
>    if (false_edge->dest == middle_bb)
>      false_edge = EDGE_SUCC (false_edge->dest, 0);
>  
> +  /* When THREEWAY_P then e1 will point to the edge of the final transition
> +     from middle-bb to end.  */
>    if (true_edge == e0)
>      {
> -      gcc_assert (false_edge == e1);
> +      if (!threeway_p)
> +	gcc_assert (false_edge == e1);
>        arg_true = arg0;
>        arg_false = arg1;
>      }
>    else
>      {
>        gcc_assert (false_edge == e0);
> -      gcc_assert (true_edge == e1);
> +      if (!threeway_p)
> +	gcc_assert (true_edge == e1);
>        arg_true = arg1;
>        arg_false = arg0;
>      }
> @@ -1937,6 +1992,165 @@ minmax_replacement (basic_block cond_bb, basic_block middle_bb,
>        else
>  	return false;
>      }
> +  else if (middle_bb != alt_middle_bb && threeway_p)
> +    {
> +      /* Recognize the following case:
> +
> +	 if (smaller < larger)
> +	   a = MIN (smaller, c);
> +	 else
> +	   b = MIN (larger, c);
> +	 x = PHI <a, b>
> +
> +	 This is equivalent to
> +
> +	 a = MIN (smaller, c);
> +	 x = MIN (larger, a);  */
> +
> +      gimple *assign = last_and_only_stmt (middle_bb);
> +      tree lhs, op0, op1, bound;
> +      tree alt_lhs, alt_op0, alt_op1;
> +      bool invert = false;
> +
> +      if (!single_pred_p (middle_bb)
> +	  || !single_pred_p (alt_middle_bb)
> +	  || !single_succ_p (middle_bb)
> +	  || !single_succ_p (alt_middle_bb))
> +	return false;
> +
> +      /* When THREEWAY_P then e1 will point to the edge of the final transition
> +	 from middle-bb to end.  */
> +      if (true_edge == e0)
> +	gcc_assert (false_edge == EDGE_PRED (e1->src, 0));
> +      else
> +	gcc_assert (true_edge == EDGE_PRED (e1->src, 0));
> +
> +      bool valid_minmax_p = false;
> +      gimple_stmt_iterator it1
> +	= gsi_start_nondebug_after_labels_bb (middle_bb);
> +      gimple_stmt_iterator it2
> +	= gsi_start_nondebug_after_labels_bb (alt_middle_bb);
> +      if (gsi_one_nondebug_before_end_p (it1)
> +	  && gsi_one_nondebug_before_end_p (it2))
> +	{
> +	  gimple *stmt1 = gsi_stmt (it1);
> +	  gimple *stmt2 = gsi_stmt (it2);
> +	  if (is_gimple_assign (stmt1) && is_gimple_assign (stmt2))
> +	    {
> +	      enum tree_code code1 = gimple_assign_rhs_code (stmt1);
> +	      enum tree_code code2 = gimple_assign_rhs_code (stmt2);
> +	      valid_minmax_p = (code1 == MIN_EXPR || code1 == MAX_EXPR)
> +			       && (code2 == MIN_EXPR || code2 == MAX_EXPR);
> +	    }
> +	}
> +
> +      if (!valid_minmax_p)
> +	return false;
> +
> +      if (!assign
> +	  || gimple_code (assign) != GIMPLE_ASSIGN)
> +	return false;
> +
> +      lhs = gimple_assign_lhs (assign);
> +      ass_code = gimple_assign_rhs_code (assign);
> +      if (ass_code != MAX_EXPR && ass_code != MIN_EXPR)
> +	return false;
> +
> +      op0 = gimple_assign_rhs1 (assign);
> +      op1 = gimple_assign_rhs2 (assign);
> +
> +      assign = last_and_only_stmt (alt_middle_bb);
> +      if (!assign
> +	  || gimple_code (assign) != GIMPLE_ASSIGN)
> +	return false;
> +
> +      alt_lhs = gimple_assign_lhs (assign);
> +      if (ass_code != gimple_assign_rhs_code (assign))
> +	return false;
> +
> +      if (!operand_equal_for_phi_arg_p (lhs, arg_true)
> +	 || !operand_equal_for_phi_arg_p (alt_lhs, arg_false))
> +	return false;
> +
> +      alt_op0 = gimple_assign_rhs1 (assign);
> +      alt_op1 = gimple_assign_rhs2 (assign);
> +
> +      if ((operand_equal_for_phi_arg_p (op0, smaller)
> +		|| (alt_smaller
> +		    && operand_equal_for_phi_arg_p (op0, alt_smaller)))
> +	       && (operand_equal_for_phi_arg_p (alt_op0, larger)
> +		   || (alt_larger
> +		       && operand_equal_for_phi_arg_p (alt_op0, alt_larger))))
> +	{
> +	  /* We got here if the condition is true, i.e., SMALLER < LARGER.  */
> +	  if (!operand_equal_for_phi_arg_p (op1, alt_op1))
> +	    return false;
> +
> +	  if ((arg0 = strip_bit_not (op0)) != NULL
> +	      && (arg1 = strip_bit_not (alt_op0)) != NULL
> +	      && (bound = strip_bit_not (op1)) != NULL)
> +	    {
> +	      minmax = MAX_EXPR;
> +	      ass_code = invert_minmax_code (ass_code);
> +	      invert = true;
> +	    }
> +	  else
> +	    {
> +	      bound = op1;
> +	      minmax = MIN_EXPR;
> +	      arg0 = op0;
> +	      arg1 = alt_op0;
> +	     }
> +	}
> +      else if ((operand_equal_for_phi_arg_p (op0, larger)
> +		|| (alt_larger
> +		    && operand_equal_for_phi_arg_p (op0, alt_larger)))
> +	       && (operand_equal_for_phi_arg_p (alt_op0, smaller)
> +		   || (alt_smaller
> +		       && operand_equal_for_phi_arg_p (alt_op0, alt_smaller))))
> +	{
> +	  /* We got here if the condition is true, i.e., SMALLER > LARGER.  */
> +	  if (!operand_equal_for_phi_arg_p (op1, alt_op1))
> +	    return false;
> +
> +	  if ((arg0 = strip_bit_not (op0)) != NULL
> +	      && (arg1 = strip_bit_not (alt_op0)) != NULL
> +	      && (bound = strip_bit_not (op1)) != NULL)
> +	    {
> +	      minmax = MIN_EXPR;
> +	      ass_code = invert_minmax_code (ass_code);
> +	      invert = true;
> +	    }
> +	  else
> +	    {
> +	      bound = op1;
> +	      minmax = MAX_EXPR;
> +	      arg0 = op0;
> +	      arg1 = alt_op0;
> +	     }
> +	}
> +      else
> +	return false;
> +
> +      /* Emit the statement to compute min/max.  */
> +      location_t locus = gimple_location (last_stmt (cond_bb));
> +      gimple_seq stmts = NULL;
> +      tree phi_result = PHI_RESULT (phi);
> +      result = gimple_build (&stmts, locus, minmax, TREE_TYPE (phi_result),
> +			     arg0, bound);
> +      result = gimple_build (&stmts, locus, ass_code, TREE_TYPE (phi_result),
> +			     result, arg1);
> +      if (invert)
> +	result = gimple_build (&stmts, locus, BIT_NOT_EXPR, TREE_TYPE (phi_result),
> +			       result);
> +
> +      gsi = gsi_last_bb (cond_bb);
> +      gsi_insert_seq_before (&gsi, stmts, GSI_NEW_STMT);
> +
> +      replace_phi_edge_with_variable (cond_bb, e1, phi, result, false);
> +
> +      return true;
> +    }
>    else
>      {
>        /* Recognize the following case, assuming d <= u:
> 

-- 
Richard Biener <rguenther@suse.de>
SUSE Software Solutions Germany GmbH, Frankenstrasse 146, 90461 Nuernberg,
Germany; GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman;
HRB 36809 (AG Nuernberg)