[PATCH] Fix thinko in operator_bitwise_xor::op1_range

[PATCH] Fix thinko in operator_bitwise_xor::op1_range

[Eric Botcazou]

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Hi,

there is a thinko in the op1_range method of ranger's operator_bitwise_xor 
class in a boolean context: if the result is known to be true, it may infer 
than a specific operand is false without any basis.

Tested on x86-64/Linux, OK for mainline, 12 and 11 branches?


2022-11-25  Eric Botcazou  <ebotcazou@adacore.com>

	* range-op.cc (operator_bitwise_xor::op1_range): Fix thinko.


2022-11-25  Eric Botcazou  <ebotcazou@adacore.com>

	* gnat.dg/opt100.adb: New test.
	* gnat.dg/opt100_pkg.adb, gnat.dg/opt100_pkg.ads: New helper.

-- 
Eric Botcazou

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diff --git a/gcc/range-op.cc b/gcc/range-op.cc
index 6fa3b151596..daea084ce18 100644
--- a/gcc/range-op.cc
+++ b/gcc/range-op.cc
@@ -3501,6 +3501,9 @@ operator_bitwise_xor::op1_range (irange &r, tree type,
 	    r.set_varying (type);
 	  else if (op2.zero_p ())
 	    r = range_true (type);
+	  // See get_bool_state for the rationale
+	  else if (op2.contains_p (build_zero_cst (op2.type ())))
+	    r = range_true_and_false (type);
 	  else
 	    r = range_false (type);
 	  break;

[-- Attachment #3: opt100.adb --]
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-- { dg-do run }
-- { dg-options "-O2 -gnatp" }

with Opt100_Pkg; use Opt100_Pkg;

procedure Opt100 is
  R : constant Rec := (K => B, N => 1);

begin
  if Func (R) /= 1 then
     raise Program_Error;
  end if;
end;

[-- Attachment #4: opt100_pkg.adb --]
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package body Opt100_Pkg is

   function Func (R : Rec) return Integer is
   begin
      if R in Small_Rec then
         case R.K is
            when A => return 0;
            when B => return 1;
            when C => return 2;
            when others => raise Program_Error;
         end case;
      else
         return -1;
      end if;
   end;

end Opt100_Pkg;

[-- Attachment #5: opt100_pkg.ads --]
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with Interfaces; use Interfaces;

package Opt100_Pkg is

  A : constant Unsigned_8 := 0;
  B : constant Unsigned_8 := 1;
  C : constant Unsigned_8 := 2;

  subtype Small_Unsigned_8 is Unsigned_8 range A .. C;

  type Rec is record
    K : Unsigned_8;
    N : Natural;
  end record;

  subtype Small_Rec is Rec
    with Dynamic_Predicate =>
      Small_Rec.K in Small_Unsigned_8 and
        ((Small_Rec.N in Positive) = (Small_Rec.K in B | C));

   function Func (R : Rec) return Integer;

end Opt100_Pkg;

Re: [PATCH] Fix thinko in operator_bitwise_xor::op1_range

[Richard Biener]

On Fri, Nov 25, 2022 at 10:22 AM Eric Botcazou via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
> Hi,
>
> there is a thinko in the op1_range method of ranger's operator_bitwise_xor
> class in a boolean context: if the result is known to be true, it may infer
> than a specific operand is false without any basis.
>
> Tested on x86-64/Linux, OK for mainline, 12 and 11 branches?

OK.

Thanks,
Richard.

>
> 2022-11-25  Eric Botcazou  <ebotcazou@adacore.com>
>
>         * range-op.cc (operator_bitwise_xor::op1_range): Fix thinko.
>
>
> 2022-11-25  Eric Botcazou  <ebotcazou@adacore.com>
>
>         * gnat.dg/opt100.adb: New test.
>         * gnat.dg/opt100_pkg.adb, gnat.dg/opt100_pkg.ads: New helper.
>
> --
> Eric Botcazou