[RFC][PR64946] "abs" vectorization fails for char/short types

Kugan Vivekanandarajah kugan.vivekanandarajah@linaro.org
Mon Jun 4 08:18:00 GMT 2018


Hi Richard,

Thanks for the review.

On 1 June 2018 at 22:20, Richard Biener <richard.guenther@gmail.com> wrote:
> On Fri, Jun 1, 2018 at 4:12 AM Kugan Vivekanandarajah
> <kugan.vivekanandarajah@linaro.org> wrote:
>>
>> Hi Richard,
>>
>> This is the revised patch based on the review and the discussion in
>> https://gcc.gnu.org/ml/gcc/2018-05/msg00179.html.
>>
>> In summary:
>> - I skipped  (element_precision (type) < element_precision (TREE_TYPE
>> (@0))) in the match.pd pattern as this would prevent transformation
>> for the case in PR.
>> that is, I am interested in is something like:
>>   char t = (char) ABS_EXPR <(int) x>
>> and I want to generate
>> char t = (char) ABSU_EXPR <x>
>>
>> - I also haven't added all the necessary match.pd changes for
>> ABSU_EXPR. I have a patch for that but will submit separately based on
>> this reveiw.
>>
>> - I also tried to add ABSU_EXPRsupport  in the places as necessary by
>> grepping for ABS_EXPR.
>>
>> - I also had to add special casing in vectorizer for ABSU_EXP as its
>> result is unsigned type.
>>
>> Is this OK. Patch bootstraps and the regression test is ongoing.
>
> The c/c-typeck.c:build_unary_op change looks unnecessary - the
> C FE should never generate this directly (the c-common one might
> be triggered by early folding I guess).

The Gimple FE testcase is running into this.

>
> @@ -1761,6 +1762,9 @@ const_unop (enum tree_code code, tree type, tree arg0)
>        if (TREE_CODE (arg0) == INTEGER_CST || TREE_CODE (arg0) == REAL_CST)
>         return fold_abs_const (arg0, type);
>        break;
> +    case ABSU_EXPR:
> +       return fold_convert (type, fold_abs_const (arg0,
> +                                                  signed_type_for (type)));
>
>      case CONJ_EXPR:
>
> I think this will get you bogus TREE_OVERFLOW flags set on ABSU (-INT_MIN).
>
> I think you want to change fold_abs_const to properly deal with arg0 being
> signed and type unsigned.  That is, sth like
>
> diff --git a/gcc/fold-const.c b/gcc/fold-const.c
> index 6f80f1b1d69..f60f9c77e91 100644
> --- a/gcc/fold-const.c
> +++ b/gcc/fold-const.c
> @@ -13843,18 +13843,19 @@ fold_abs_const (tree arg0, tree type)
>        {
>          /* If the value is unsigned or non-negative, then the absolute value
>            is the same as the ordinary value.  */
> -       if (!wi::neg_p (wi::to_wide (arg0), TYPE_SIGN (type)))
> -         t = arg0;
> +       wide_int val = wi::to_wide (arg0);
> +       bool overflow = false;
> +       if (!wi::neg_p (val, TYPE_SIGN (TREE_TYPE (arg0))))
> +         ;
>
>         /* If the value is negative, then the absolute value is
>            its negation.  */
>         else
> -         {
> -           bool overflow;
> -           wide_int val = wi::neg (wi::to_wide (arg0), &overflow);
> -           t = force_fit_type (type, val, -1,
> -                               overflow | TREE_OVERFLOW (arg0));
> -         }
> +         wide_int val = wi::neg (val, &overflow);
> +
> +       /* Force to the destination type, set TREE_OVERFLOW for signed
> +          TYPE only.  */
> +       t = force_fit_type (type, val, 1, overflow | TREE_OVERFLOW (arg0));
>        }
>        break;
>
> and then simply share the const_unop code with ABS_EXPR.

Done.

> diff --git a/gcc/match.pd b/gcc/match.pd
> index 14386da..7d7c132 100644
> --- a/gcc/match.pd
> +++ b/gcc/match.pd
> @@ -102,6 +102,14 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
>  (match (nop_convert @0)
>   @0)
>
> +(simplify (abs (convert @0))
> + (if (ANY_INTEGRAL_TYPE_P (TREE_TYPE (@0))
> +      && !TYPE_UNSIGNED (TREE_TYPE (@0))
> +      && !TYPE_UNSIGNED (type))
> +  (with { tree utype = unsigned_type_for (TREE_TYPE (@0)); }
> +   (convert (absu:utype @0)))))
> +
> +
>
> please put a comment before the pattern.  I believe there's no
> need to check for !TYPE_UNSIGNED (type).  Note this
> also converts abs ((char)int-var) to (char)absu(int-var) which
> doesn't make sense.  The original issue you want to address
> here is the case where TYPE_PRECISION of @0 is less than
> the precision of type.  That is, you want to remove language
> introduced integer promotion of @0 which only is possible
> with ABSU.  So please do add such precision check
> (I simply suggested the bogus direction of the test).

Done.
>
> diff --git a/gcc/tree-cfg.c b/gcc/tree-cfg.c
> index 68f4fd3..9b62583 100644
> --- a/gcc/tree-cfg.c
> +++ b/gcc/tree-cfg.c
> @@ -3685,6 +3685,12 @@ verify_gimple_assign_unary (gassign *stmt)
>      case PAREN_EXPR:
>      case CONJ_EXPR:
>        break;
> +    case ABSU_EXPR:
> +      if (!TYPE_UNSIGNED (lhs_type)
> +         || !ANY_INTEGRAL_TYPE_P (rhs1_type))
>
>  if (!ANY_INTEGRAL_TYPE_P (lhs_type)
>      || !TYPE_UNSIGNED (lhs_type)
>      || !ANY_INTEGRAL_TYPE_P (rhs1_type)
>      || TYPE_UNSIGNED (rhs1_type)
>      || element_precision (lhs_type) != element_precision (rhs1_type))
>   {
>       error ("invalid types for ABSU_EXPR");
>       debug_generic_expr (lhs_type);
>       debug_generic_expr (rhs1_type);
>      return true;
>   }
>
> +       return true;
> +      return false;
> +      break;
>
> diff --git a/gcc/tree-eh.c b/gcc/tree-eh.c
> index 30c6d9e..44b1399 100644
> --- a/gcc/tree-eh.c
> +++ b/gcc/tree-eh.c
> @@ -2465,6 +2465,7 @@ operation_could_trap_helper_p (enum tree_code op,
>
>      case NEGATE_EXPR:
>      case ABS_EXPR:
> +    case ABSU_EXPR:
>      case CONJ_EXPR:
>        /* These operations don't trap with floating point.  */
>        if (honor_trapv)
>
> ABSU never traps.  Please instead unconditionally return false.
Done.

>
> diff --git a/gcc/tree-vect-stmts.c b/gcc/tree-vect-stmts.c
> index 66c78de..b52d714 100644
> --- a/gcc/tree-vect-stmts.c
> +++ b/gcc/tree-vect-stmts.c
> @@ -5995,7 +5995,11 @@ vectorizable_operation (gimple *stmt,
> gimple_stmt_iterator *gsi,
>                       "transform binary/unary operation.\n");
>
>    /* Handle def.  */
> -  vec_dest = vect_create_destination_var (scalar_dest, vectype);
> +  if (code == ABSU_EXPR)
> +    vec_dest = vect_create_destination_var (scalar_dest,
> +                                           unsigned_type_for (vectype));
> +  else
> +    vec_dest = vect_create_destination_var (scalar_dest, vectype);
>
>    /* POINTER_DIFF_EXPR has pointer arguments which are vectorized as
>       vectors with unsigned elements, but the result is signed.  So, we
>
> simply use vectype_out for creation of vec_dest.
Done.

>
> diff --git a/gcc/tree.def b/gcc/tree.def
> index c660b2c..5fec781 100644
> --- a/gcc/tree.def
> +++ b/gcc/tree.def
> @@ -760,6 +760,7 @@ DEFTREECODE (MAX_EXPR, "max_expr", tcc_binary, 2)
>     An ABS_EXPR must have either an INTEGER_TYPE or a REAL_TYPE.  The
>     operand of the ABS_EXPR must have the same type.  */
>  DEFTREECODE (ABS_EXPR, "abs_expr", tcc_unary, 1)
> +DEFTREECODE (ABSU_EXPR, "absu_expr", tcc_unary, 1)
>
>  /* Shift operations for shift and rotate.
>     Shift means logical shift if done on an
>
> You can clearly see that the comment before ABS_EXPR doesn't apply to ABSU_EXPR
> so please add an appropriate one.  I suggest
>
> /* Represents the unsigned absolute value of the operand.
>     An ABSU_EXPR must have unsigned INTEGER_TYPE.  The operand of the ABSU_EXPR
>     must have the corresponding signed type.  */

Done.

Here is the reviesed patch. Is this OK?

Thanks,
Kugan

>
> Otherwise looks OK.  (I didn't explicitely check for missing ABSU_EXPR
> handling this time)
>
> Thanks,
> Richard.
>
>
>> Thanks,
>> Kugan
>>
>>
>> On 18 May 2018 at 12:36, Kugan Vivekanandarajah
>> <kugan.vivekanandarajah@linaro.org> wrote:
>> > Hi Richard,
>> >
>> > Thanks for the review. I am revising the patch based on Andrew's comments too.
>> >
>> > On 17 May 2018 at 20:36, Richard Biener <richard.guenther@gmail.com> wrote:
>> >> On Thu, May 17, 2018 at 4:56 AM Andrew Pinski <pinskia@gmail.com> wrote:
>> >>
>> >>> On Wed, May 16, 2018 at 7:14 PM, Kugan Vivekanandarajah
>> >>> <kugan.vivekanandarajah@linaro.org> wrote:
>> >>> > As mentioned in the PR, I am trying to add ABSU_EXPR to fix this
>> >>> > issue. In the attached patch, in fold_cond_expr_with_comparison I am
>> >>> > generating ABSU_EXPR for these cases. As I understand, absu_expr is
>> >>> > well defined in RTL. So, the issue is generating absu_expr  and
>> >>> > transferring to RTL in the correct way. I am not sure I am not doing
>> >>> > all that is needed. I will clean up and add more test-cases based on
>> >>> > the feedback.
>> >>
>> >>
>> >>> diff --git a/gcc/optabs-tree.c b/gcc/optabs-tree.c
>> >>> index 71e172c..2b812e5 100644
>> >>> --- a/gcc/optabs-tree.c
>> >>> +++ b/gcc/optabs-tree.c
>> >>> @@ -235,6 +235,7 @@ optab_for_tree_code (enum tree_code code, const_tree
>> >> type,
>> >>>         return trapv ? negv_optab : neg_optab;
>> >>
>> >>>       case ABS_EXPR:
>> >>> +    case ABSU_EXPR:
>> >>>         return trapv ? absv_optab : abs_optab;
>> >>
>> >>
>> >>> This part is not correct, it should something like this:
>> >>
>> >>>       case ABS_EXPR:
>> >>>         return trapv ? absv_optab : abs_optab;
>> >>> +    case ABSU_EXPR:
>> >>> +       return abs_optab ;
>> >>
>> >>> Because ABSU is not undefined at the TYPE_MAX.
>> >>
>> >> Also
>> >>
>> >>         /* Unsigned abs is simply the operand.  Testing here means we don't
>> >>           risk generating incorrect code below.  */
>> >> -      if (TYPE_UNSIGNED (type))
>> >> +      if (TYPE_UNSIGNED (type)
>> >> +         && (code != ABSU_EXPR))
>> >>          return op0;
>> >>
>> >> is wrong.  ABSU of an unsigned number is still just that number.
>> >>
>> >> The change to fold_cond_expr_with_comparison looks odd to me
>> >> (premature optimization).  It should be done separately - it seems
>> >> you are doing
>> >
>> > FE seems to be using this to generate ABS_EXPR from
>> > c_fully_fold_internal to fold_build3_loc and so on. I changed this to
>> > generate ABSU_EXPR for the case in the testcase. So the question
>> > should be, in what cases do we need ABS_EXPR and in what cases do we
>> > need ABSU_EXPR. It is not very clear to me.
>> >
>> >
>> >>
>> >> (simplify (abs (convert @0)) (convert (absu @0)))
>> >>
>> >> here.
>> >>
>> >> You touch one other place in fold-const.c but there seem to be many
>> >> more that need ABSU_EXPR handling (you touched the one needed
>> >> for correctness) - esp. you should at least handle constant folding
>> >> in const_unop and the nonnegative predicate.
>> >
>> > OK.
>> >>
>> >> @@ -3167,6 +3167,9 @@ verify_expr (tree *tp, int *walk_subtrees, void *data
>> >> ATTRIBUTE_UNUSED)
>> >>         CHECK_OP (0, "invalid operand to unary operator");
>> >>         break;
>> >>
>> >> +    case ABSU_EXPR:
>> >> +      break;
>> >> +
>> >>       case REALPART_EXPR:
>> >>       case IMAGPART_EXPR:
>> >>
>> >> verify_expr is no more.  Did you test this recently against trunk?
>> >
>> > This patch is against slightly older trunk. I will rebase it.
>> >
>> >>
>> >> @@ -3937,6 +3940,9 @@ verify_gimple_assign_unary (gassign *stmt)
>> >>       case PAREN_EXPR:
>> >>       case CONJ_EXPR:
>> >>         break;
>> >> +    case ABSU_EXPR:
>> >> +      /* FIXME.  */
>> >> +      return false;
>> >>
>> >> no - please not!  Please add verification here - ABSU should be only
>> >> called on INTEGRAL, vector or complex INTEGRAL types and the
>> >> type of the LHS should be always the unsigned variant of the
>> >> argument type.
>> >
>> > OK.
>> >>
>> >>     if (is_gimple_val (cond_expr))
>> >>       return cond_expr;
>> >>
>> >> -  if (TREE_CODE (cond_expr) == ABS_EXPR)
>> >> +  if (TREE_CODE (cond_expr) == ABS_EXPR
>> >> +      || TREE_CODE (cond_expr) == ABSU_EXPR)
>> >>       {
>> >>         rhs1 = TREE_OPERAND (cond_expr, 1);
>> >>         STRIP_USELESS_TYPE_CONVERSION (rhs1);
>> >>
>> >> err, but the next line just builds a ABS_EXPR ...
>> >>
>> >> How did you identify spots that need adjustment?  I would expect that
>> >> once folding generates ABSU_EXPR that you need to adjust frontends
>> >> (C++ constexpr handling for example).  Also I miss adjustments
>> >> to gimple-pretty-print.c and the GIMPLE FE parser.
>> >
>> > I will add this.
>> >>
>> >> recursively grepping throughout the whole gcc/ tree doesn't reveal too many
>> >> cases of ABS_EXPR so I think it's reasonable to audit all of them.
>> >>
>> >> I also miss some trivial absu simplifications in match.pd.  There are not
>> >> a lot of abs cases but similar ones would be good to have initially.
>> >
>> > I will add them in the next version.
>> >
>> > Thanks,
>> > Kugan
>> >
>> >>
>> >> Thanks for tackling this!
>> >> Richard.
>> >>
>> >>> Thanks,
>> >>> Andrew
>> >>
>> >>> >
>> >>> > Thanks,
>> >>> > Kugan
>> >>> >
>> >>> >
>> >>> > gcc/ChangeLog:
>> >>> >
>> >>> > 2018-05-13  Kugan Vivekanandarajah  <kugan.vivekanandarajah@linaro.org>
>> >>> >
>> >>> >     * expr.c (expand_expr_real_2): Handle ABSU_EXPR.
>> >>> >     * fold-const.c (fold_cond_expr_with_comparison): Generate ABSU_EXPR
>> >>> >     (fold_unary_loc): Handle ABSU_EXPR.
>> >>> >     * optabs-tree.c (optab_for_tree_code): Likewise.
>> >>> >     * tree-cfg.c (verify_expr): Likewise.
>> >>> >     (verify_gimple_assign_unary):  Likewise.
>> >>> >     * tree-if-conv.c (fold_build_cond_expr):  Likewise.
>> >>> >     * tree-inline.c (estimate_operator_cost):  Likewise.
>> >>> >     * tree-pretty-print.c (dump_generic_node):  Likewise.
>> >>> >     * tree.def (ABSU_EXPR): New.
>> >>> >
>> >>> > gcc/testsuite/ChangeLog:
>> >>> >
>> >>> > 2018-05-13  Kugan Vivekanandarajah  <kugan.vivekanandarajah@linaro.org>
>> >>> >
>> >>> >     * gcc.dg/absu.c: New test.
-------------- next part --------------
diff --git a/gcc/c-family/c-common.c b/gcc/c-family/c-common.c
index 859eeb4..0e8efb5 100644
--- a/gcc/c-family/c-common.c
+++ b/gcc/c-family/c-common.c
@@ -3312,6 +3312,7 @@ c_common_truthvalue_conversion (location_t location, tree expr)
 
     case NEGATE_EXPR:
     case ABS_EXPR:
+    case ABSU_EXPR:
     case FLOAT_EXPR:
     case EXCESS_PRECISION_EXPR:
       /* These don't change whether an object is nonzero or zero.  */
diff --git a/gcc/c/c-typeck.c b/gcc/c/c-typeck.c
index 45a4529..5bb6804 100644
--- a/gcc/c/c-typeck.c
+++ b/gcc/c/c-typeck.c
@@ -4314,6 +4314,16 @@ build_unary_op (location_t location, enum tree_code code, tree xarg,
 	arg = default_conversion (arg);
       break;
 
+    case ABSU_EXPR:
+      if (!(typecode == INTEGER_TYPE))
+	{
+	  error_at (location, "wrong type argument to absu");
+	  return error_mark_node;
+	}
+      else if (!noconvert)
+	arg = default_conversion (arg);
+      break;
+
     case CONJ_EXPR:
       /* Conjugating a real value is a no-op, but allow it anyway.  */
       if (!(typecode == INTEGER_TYPE || typecode == REAL_TYPE
diff --git a/gcc/c/gimple-parser.c b/gcc/c/gimple-parser.c
index c9abe24..11e76ff 100644
--- a/gcc/c/gimple-parser.c
+++ b/gcc/c/gimple-parser.c
@@ -328,7 +328,8 @@ c_parser_gimple_statement (c_parser *parser, gimple_seq *seq)
     case CPP_NAME:
       {
 	tree id = c_parser_peek_token (parser)->value;
-	if (strcmp (IDENTIFIER_POINTER (id), "__ABS") == 0)
+	if (strcmp (IDENTIFIER_POINTER (id), "__ABS") == 0
+	    || strcmp (IDENTIFIER_POINTER (id), "__ABSU") == 0)
 	  goto build_unary_expr;
 	break;
       }
@@ -638,6 +639,12 @@ c_parser_gimple_unary_expression (c_parser *parser)
 	      op = c_parser_gimple_postfix_expression (parser);
 	      return parser_build_unary_op (op_loc, ABS_EXPR, op);
 	    }
+	  else if (strcmp (IDENTIFIER_POINTER (id), "__ABSU") == 0)
+	    {
+	      c_parser_consume_token (parser);
+	      op = c_parser_gimple_postfix_expression (parser);
+	      return parser_build_unary_op (op_loc, ABSU_EXPR, op);
+	    }
 	  else
 	    return c_parser_gimple_postfix_expression (parser);
 	}
diff --git a/gcc/cfgexpand.c b/gcc/cfgexpand.c
index ef143a3..ba4543c 100644
--- a/gcc/cfgexpand.c
+++ b/gcc/cfgexpand.c
@@ -4621,6 +4621,7 @@ expand_debug_expr (tree exp)
       }
 
     case ABS_EXPR:
+    case ABSU_EXPR:
       return simplify_gen_unary (ABS, mode, op0, mode);
 
     case NEGATE_EXPR:
diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
index e19864d..487127c 100644
--- a/gcc/config/i386/i386.c
+++ b/gcc/config/i386/i386.c
@@ -51228,6 +51228,7 @@ ix86_add_stmt_cost (void *data, int count, enum vect_cost_for_stmt kind,
 
 	case BIT_IOR_EXPR:
 	case ABS_EXPR:
+	case ABSU_EXPR:
 	case MIN_EXPR:
 	case MAX_EXPR:
 	case BIT_XOR_EXPR:
diff --git a/gcc/cp/constexpr.c b/gcc/cp/constexpr.c
index 8c6ec55..bea9147 100644
--- a/gcc/cp/constexpr.c
+++ b/gcc/cp/constexpr.c
@@ -5760,6 +5760,7 @@ potential_constant_expression_1 (tree t, bool want_rval, bool strict, bool now,
     case FLOAT_EXPR:
     case NEGATE_EXPR:
     case ABS_EXPR:
+    case ABSU_EXPR:
     case TRUTH_NOT_EXPR:
     case FIXED_CONVERT_EXPR:
     case UNARY_PLUS_EXPR:
diff --git a/gcc/cp/cp-gimplify.c b/gcc/cp/cp-gimplify.c
index eda5f05..bca0c59 100644
--- a/gcc/cp/cp-gimplify.c
+++ b/gcc/cp/cp-gimplify.c
@@ -2271,6 +2271,7 @@ cp_fold (tree x)
     case FLOAT_EXPR:
     case NEGATE_EXPR:
     case ABS_EXPR:
+    case ABSU_EXPR:
     case BIT_NOT_EXPR:
     case TRUTH_NOT_EXPR:
     case FIXED_CONVERT_EXPR:
diff --git a/gcc/dojump.c b/gcc/dojump.c
index 9da8a0e..88cc96a 100644
--- a/gcc/dojump.c
+++ b/gcc/dojump.c
@@ -467,6 +467,7 @@ do_jump (tree exp, rtx_code_label *if_false_label,
       /* FALLTHRU */
     case NON_LVALUE_EXPR:
     case ABS_EXPR:
+    case ABSU_EXPR:
     case NEGATE_EXPR:
     case LROTATE_EXPR:
     case RROTATE_EXPR:
diff --git a/gcc/expr.c b/gcc/expr.c
index 00a802c..9efa535 100644
--- a/gcc/expr.c
+++ b/gcc/expr.c
@@ -9074,6 +9074,7 @@ expand_expr_real_2 (sepops ops, rtx target, machine_mode tmode,
       return REDUCE_BIT_FIELD (temp);
 
     case ABS_EXPR:
+    case ABSU_EXPR:
       op0 = expand_expr (treeop0, subtarget,
 			 VOIDmode, EXPAND_NORMAL);
       if (modifier == EXPAND_STACK_PARM)
@@ -9085,7 +9086,7 @@ expand_expr_real_2 (sepops ops, rtx target, machine_mode tmode,
 
       /* Unsigned abs is simply the operand.  Testing here means we don't
 	 risk generating incorrect code below.  */
-      if (TYPE_UNSIGNED (type))
+      if (TYPE_UNSIGNED (TREE_TYPE (treeop0)))
 	return op0;
 
       return expand_abs (mode, op0, target, unsignedp,
diff --git a/gcc/fold-const.c b/gcc/fold-const.c
index faa184a..c19614e 100644
--- a/gcc/fold-const.c
+++ b/gcc/fold-const.c
@@ -1723,7 +1723,8 @@ const_unop (enum tree_code code, tree type, tree arg0)
       && HONOR_SNANS (TYPE_MODE (TREE_TYPE (arg0)))
       && REAL_VALUE_ISSIGNALING_NAN (TREE_REAL_CST (arg0))
       && code != NEGATE_EXPR
-      && code != ABS_EXPR)
+      && code != ABS_EXPR
+      && code != ABSU_EXPR)
     return NULL_TREE;
 
   switch (code)
@@ -1758,6 +1759,7 @@ const_unop (enum tree_code code, tree type, tree arg0)
       }
 
     case ABS_EXPR:
+    case ABSU_EXPR:
       if (TREE_CODE (arg0) == INTEGER_CST || TREE_CODE (arg0) == REAL_CST)
 	return fold_abs_const (arg0, type);
       break;
@@ -13846,20 +13848,21 @@ fold_abs_const (tree arg0, tree type)
       {
         /* If the value is unsigned or non-negative, then the absolute value
 	   is the same as the ordinary value.  */
-	if (!wi::neg_p (wi::to_wide (arg0), TYPE_SIGN (type)))
-	  t = arg0;
+	wide_int val = wi::to_wide (arg0);
+	bool overflow = false;
+	if (!wi::neg_p (val, TYPE_SIGN (TREE_TYPE (arg0))))
+	  ;
 
 	/* If the value is negative, then the absolute value is
 	   its negation.  */
 	else
-	  {
-	    bool overflow;
-	    wide_int val = wi::neg (wi::to_wide (arg0), &overflow);
-	    t = force_fit_type (type, val, -1,
-				overflow | TREE_OVERFLOW (arg0));
-	  }
+	  val = wi::neg (val, &overflow);
+
+	/* Force to the destination type, set TREE_OVERFLOW for signed
+	   TYPE only.  */
+	t = force_fit_type (type, val, 1, overflow | TREE_OVERFLOW (arg0));
       }
-      break;
+    break;
 
     case REAL_CST:
       if (REAL_VALUE_NEGATIVE (TREE_REAL_CST (arg0)))
diff --git a/gcc/gimple-pretty-print.c b/gcc/gimple-pretty-print.c
index afe0147..4fa992d 100644
--- a/gcc/gimple-pretty-print.c
+++ b/gcc/gimple-pretty-print.c
@@ -358,14 +358,17 @@ dump_unary_rhs (pretty_printer *buffer, gassign *gs, int spc,
       break;
 
     case ABS_EXPR:
+    case ABSU_EXPR:
       if (flags & TDF_GIMPLE)
 	{
-	  pp_string (buffer, "__ABS ");
+	  pp_string (buffer,
+		     rhs_code == ABS_EXPR ? "__ABS " : "__ABSU ");
 	  dump_generic_node (buffer, rhs, spc, flags, false);
 	}
       else
 	{
-	  pp_string (buffer, "ABS_EXPR <");
+	  pp_string (buffer,
+		     rhs_code == ABS_EXPR ? "ABS_EXPR <" : "ABSU_EXPR <");
 	  dump_generic_node (buffer, rhs, spc, flags, false);
 	  pp_greater (buffer);
 	}
diff --git a/gcc/gimple-ssa-backprop.c b/gcc/gimple-ssa-backprop.c
index 27aa575..a38b5eb 100644
--- a/gcc/gimple-ssa-backprop.c
+++ b/gcc/gimple-ssa-backprop.c
@@ -405,6 +405,7 @@ backprop::process_assign_use (gassign *assign, tree rhs, usage_info *info)
   switch (gimple_assign_rhs_code (assign))
     {
     case ABS_EXPR:
+    case ABSU_EXPR:
       /* The sign of the input doesn't matter.  */
       info->flags.ignore_sign = true;
       break;
@@ -681,6 +682,7 @@ strip_sign_op_1 (tree rhs)
     switch (gimple_assign_rhs_code (assign))
       {
       case ABS_EXPR:
+      case ABSU_EXPR:
       case NEGATE_EXPR:
 	return gimple_assign_rhs1 (assign);
 
diff --git a/gcc/match.pd b/gcc/match.pd
index 7033730..ba52bb0 100644
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -90,6 +90,17 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
 (match (nop_convert @0)
  @0) 
 
+/* Transform likes of (char) ABS_EXPR <(int) x> into (char) ABSU_EXPR <x>
+   ABSU_EXPR returns unsigned absolute value of the operand and the operand
+   of the ABSU_EXPR will have the corresponding signed type.  */
+(simplify (abs (convert @0))
+ (if (ANY_INTEGRAL_TYPE_P (TREE_TYPE (@0))
+      && !TYPE_UNSIGNED (TREE_TYPE (@0))
+      && element_precision (type) > element_precision (TREE_TYPE (@0)))
+  (with { tree utype = unsigned_type_for (TREE_TYPE (@0)); }
+   (convert (absu:utype @0)))))
+
+
 /* Simplifications of operations with one constant operand and
    simplifications to constants or single values.  */
 
diff --git a/gcc/optabs-tree.c b/gcc/optabs-tree.c
index 71e172c..aa119ec 100644
--- a/gcc/optabs-tree.c
+++ b/gcc/optabs-tree.c
@@ -237,6 +237,8 @@ optab_for_tree_code (enum tree_code code, const_tree type,
     case ABS_EXPR:
       return trapv ? absv_optab : abs_optab;
 
+    case ABSU_EXPR:
+      return abs_optab;
     default:
       return unknown_optab;
     }
diff --git a/gcc/testsuite/gcc.dg/absu.c b/gcc/testsuite/gcc.dg/absu.c
index e69de29..063da28 100644
--- a/gcc/testsuite/gcc.dg/absu.c
+++ b/gcc/testsuite/gcc.dg/absu.c
@@ -0,0 +1,85 @@
+
+/* { dg-do run  } */
+/* { dg-options "-O0" } */
+
+#include <limits.h>
+#define ABS(x)	(((x) >= 0) ? (x) : -(x))
+
+#define DEF_TEST(TYPE)	\
+void foo_##TYPE (signed TYPE x, unsigned TYPE y){	\
+    TYPE t = ABS (x);				\
+    if (t != y)					\
+ 	__builtin_abort ();			\
+}						\
+
+DEF_TEST (char);
+DEF_TEST (short);
+DEF_TEST (int);
+DEF_TEST (long);
+
+int main ()
+{
+  foo_char (SCHAR_MIN + 1, SCHAR_MAX);
+  foo_char (0, 0);
+  foo_char (-1, 1);
+  foo_char (1, 1);
+  foo_char (SCHAR_MAX, SCHAR_MAX);
+
+  foo_int (-1, 1);
+  foo_int (0, 0);
+  foo_int (INT_MAX, INT_MAX);
+  foo_int (INT_MIN + 1, INT_MAX);
+
+  foo_short (-1, 1);
+  foo_short (0, 0);
+  foo_short (SHRT_MAX, SHRT_MAX);
+  foo_short (SHRT_MIN + 1, SHRT_MAX);
+
+  foo_long (-1, 1);
+  foo_long (0, 0);
+  foo_long (LONG_MAX, LONG_MAX);
+  foo_long (LONG_MIN + 1, LONG_MAX);
+
+  return 0;
+}
+
+/* { dg-do run  } */
+/* { dg-options "-O0" } */
+
+#include <limits.h>
+#define ABS(x)	(((x) >= 0) ? (x) : -(x))
+
+#define DEF_TEST(TYPE)	\
+void foo_##TYPE (signed TYPE x, unsigned TYPE y){	\
+    TYPE t = ABS (x);				\
+    if (t != y)					\
+ 	__builtin_abort ();			\
+}						\
+
+DEF_TEST (char);
+DEF_TEST (short);
+DEF_TEST (int);
+DEF_TEST (long);
+void main ()
+{
+  foo_char (SCHAR_MIN + 1, SCHAR_MAX);
+  foo_char (0, 0);
+  foo_char (-1, 1);
+  foo_char (1, 1);
+  foo_char (SCHAR_MAX, SCHAR_MAX);
+
+  foo_int (-1, 1);
+  foo_int (0, 0);
+  foo_int (INT_MAX, INT_MAX);
+  foo_int (INT_MIN + 1, INT_MAX);
+
+  foo_short (-1, 1);
+  foo_short (0, 0);
+  foo_short (SHRT_MAX, SHRT_MAX);
+  foo_short (SHRT_MIN + 1, SHRT_MAX);
+
+  foo_long (-1, 1);
+  foo_long (0, 0);
+  foo_long (LONG_MAX, LONG_MAX);
+  foo_long (LONG_MIN + 1, LONG_MAX);
+}
diff --git a/gcc/testsuite/gcc.dg/gimplefe-29.c b/gcc/testsuite/gcc.dg/gimplefe-29.c
index e69de29..54b86ef 100644
--- a/gcc/testsuite/gcc.dg/gimplefe-29.c
+++ b/gcc/testsuite/gcc.dg/gimplefe-29.c
@@ -0,0 +1,11 @@
+/* { dg-do compile } */
+/* { dg-options "-O -fgimple -fdump-tree-ssa-gimple" } */
+
+unsigned int __GIMPLE() f(int a)
+{
+  unsigned int t0;
+  t0_1 = __ABSU a;
+  return t0_1;
+}
+
+/* { dg-final { scan-tree-dump "__ABSU a" "ssa" } } */
diff --git a/gcc/testsuite/gcc.target/aarch64/pr64946.c b/gcc/testsuite/gcc.target/aarch64/pr64946.c
index e69de29..736656f 100644
--- a/gcc/testsuite/gcc.target/aarch64/pr64946.c
+++ b/gcc/testsuite/gcc.target/aarch64/pr64946.c
@@ -0,0 +1,13 @@
+
+/* { dg-do compile } */
+/* { dg-options "-O3" } */
+
+signed char a[100],b[100];
+void absolute_s8 (void)
+{
+  int i;
+  for (i=0; i<16; i++)
+    a[i] = (b[i] > 0 ? b[i] : -b[i]);
+};
+
+/* { dg-final { scan-assembler-times "abs\tv\[0-9\]+.16b, v\[0-9\]+.16b" 1 } } */
diff --git a/gcc/tree-cfg.c b/gcc/tree-cfg.c
index 7f48d2d..6df42cc 100644
--- a/gcc/tree-cfg.c
+++ b/gcc/tree-cfg.c
@@ -3685,6 +3685,12 @@ verify_gimple_assign_unary (gassign *stmt)
     case PAREN_EXPR:
     case CONJ_EXPR:
       break;
+    case ABSU_EXPR:
+      if (!TYPE_UNSIGNED (lhs_type)
+	  || !ANY_INTEGRAL_TYPE_P (rhs1_type))
+	return true;
+      return false;
+      break;
 
     case VEC_DUPLICATE_EXPR:
       if (TREE_CODE (lhs_type) != VECTOR_TYPE
diff --git a/gcc/tree-eh.c b/gcc/tree-eh.c
index 3609bca..da87466 100644
--- a/gcc/tree-eh.c
+++ b/gcc/tree-eh.c
@@ -2471,6 +2471,10 @@ operation_could_trap_helper_p (enum tree_code op,
 	return true;
       return false;
 
+    case ABSU_EXPR:
+      /* ABSU_EXPR never traps.  */
+      return false;
+
     case PLUS_EXPR:
     case MINUS_EXPR:
     case MULT_EXPR:
diff --git a/gcc/tree-inline.c b/gcc/tree-inline.c
index 5a0a252..d272974 100644
--- a/gcc/tree-inline.c
+++ b/gcc/tree-inline.c
@@ -3866,6 +3866,7 @@ estimate_operator_cost (enum tree_code code, eni_weights *weights,
     case MIN_EXPR:
     case MAX_EXPR:
     case ABS_EXPR:
+    case ABSU_EXPR:
 
     case LSHIFT_EXPR:
     case RSHIFT_EXPR:
diff --git a/gcc/tree-pretty-print.c b/gcc/tree-pretty-print.c
index bc36c28..612a18f 100644
--- a/gcc/tree-pretty-print.c
+++ b/gcc/tree-pretty-print.c
@@ -2463,6 +2463,12 @@ dump_generic_node (pretty_printer *pp, tree node, int spc, dump_flags_t flags,
       pp_greater (pp);
       break;
 
+    case ABSU_EXPR:
+      pp_string (pp, "ABSU_EXPR <");
+      dump_generic_node (pp, TREE_OPERAND (node, 0), spc, flags, false);
+      pp_greater (pp);
+      break;
+
     case RANGE_EXPR:
       NIY;
       break;
diff --git a/gcc/tree-vect-patterns.c b/gcc/tree-vect-patterns.c
index 5c2578f..e4df6c8 100644
--- a/gcc/tree-vect-patterns.c
+++ b/gcc/tree-vect-patterns.c
@@ -614,7 +614,8 @@ vect_recog_sad_pattern (vec<gimple *> *stmts, tree *type_in,
   gcc_assert (abs_stmt_vinfo);
   if (STMT_VINFO_DEF_TYPE (abs_stmt_vinfo) != vect_internal_def)
     return NULL;
-  if (gimple_assign_rhs_code (abs_stmt) != ABS_EXPR)
+  if (gimple_assign_rhs_code (abs_stmt) != ABS_EXPR
+      && gimple_assign_rhs_code (abs_stmt) != ABSU_EXPR)
     return NULL;
 
   tree abs_oprnd = gimple_assign_rhs1 (abs_stmt);
diff --git a/gcc/tree-vect-stmts.c b/gcc/tree-vect-stmts.c
index 4539f6a..c71b688 100644
--- a/gcc/tree-vect-stmts.c
+++ b/gcc/tree-vect-stmts.c
@@ -5995,7 +5995,10 @@ vectorizable_operation (gimple *stmt, gimple_stmt_iterator *gsi,
                      "transform binary/unary operation.\n");
 
   /* Handle def.  */
-  vec_dest = vect_create_destination_var (scalar_dest, vectype);
+  if (code == ABSU_EXPR)
+    vec_dest = vect_create_destination_var (scalar_dest, vectype_out);
+  else
+    vec_dest = vect_create_destination_var (scalar_dest, vectype);
 
   /* POINTER_DIFF_EXPR has pointer arguments which are vectorized as
      vectors with unsigned elements, but the result is signed.  So, we
diff --git a/gcc/tree.def b/gcc/tree.def
index 31de6c0..a1766e4 100644
--- a/gcc/tree.def
+++ b/gcc/tree.def
@@ -761,6 +761,11 @@ DEFTREECODE (MAX_EXPR, "max_expr", tcc_binary, 2)
    operand of the ABS_EXPR must have the same type.  */
 DEFTREECODE (ABS_EXPR, "abs_expr", tcc_unary, 1)
 
+/* Represents the unsigned absolute value of the operand.
+   An ABSU_EXPR must have unsigned INTEGER_TYPE.  The operand of the ABSU_EXPR
+   must have the corresponding signed type.  */
+DEFTREECODE (ABSU_EXPR, "absu_expr", tcc_unary, 1)
+
 /* Shift operations for shift and rotate.
    Shift means logical shift if done on an
    unsigned type, arithmetic shift if done on a signed type.


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