[PATCH] Fix PR tree-optimization/108199

[PATCH] Fix PR tree-optimization/108199

[Eric Botcazou]

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Hi,

this fixes the problematic interaction between bitfields, unions, SSO and SRA.

Tested on x86-64/Linux and SPARC/Solaris, OK for all active branches?


2023-01-11  Eric Botcazou  <ebotcazou@adacore.com>
            Andreas Krebbel  <krebbel@linux.ibm.com>

	PR tree-optimization/108199
	* tree-sra.cc (sra_modify_expr): Deal with reverse storage order
	for bit-field references.


2023-01-11  Eric Botcazou  <ebotcazou@adacore.com>

	* gcc.dg/sso-17.c: New test.

-- 
Eric Botcazou

[-- Attachment #2: pr108199.diff --]
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diff --git a/gcc/tree-sra.cc b/gcc/tree-sra.cc
index f0182a45485..ad0c738645d 100644
--- a/gcc/tree-sra.cc
+++ b/gcc/tree-sra.cc
@@ -3858,7 +3858,23 @@ sra_modify_expr (tree *expr, gimple_stmt_iterator *gsi, bool write)
 	    }
 	}
       else
-	*expr = repl;
+	{
+	  /* If we are going to replace a scalar field in a structure with
+	     reverse storage order by a stand-alone scalar, we are going to
+	     effectively byte-swap the scalar and we also need to byte-swap
+	     the portion of it represented by the bit-field.  */
+	  if (bfr && REF_REVERSE_STORAGE_ORDER (bfr))
+	    {
+	      REF_REVERSE_STORAGE_ORDER (bfr) = 0;
+	      TREE_OPERAND (bfr, 2)
+		= size_binop (MINUS_EXPR, TYPE_SIZE (TREE_TYPE (repl)),
+			      size_binop (PLUS_EXPR, TREE_OPERAND (bfr, 1),
+						     TREE_OPERAND (bfr, 2)));
+	    }
+
+	  *expr = repl;
+	}
+
       sra_stats.exprs++;
     }
   else if (write && access->grp_to_be_debug_replaced)

[-- Attachment #3: sso17.adb --]
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--  { dg-do run }
--  { dg-options "-gnatws -O" }

with System;

procedure SSO17 is

  type My_Float is new Float range 0.0 .. 359.99;

  type Rec is record
    Az : My_Float;
    El : My_Float;
  end record;
  for Rec'Bit_Order use System.High_Order_First;
  for Rec'Scalar_Storage_Order use System.High_Order_First;

  R : Rec;

  procedure Is_True (B : Boolean);
  pragma No_Inline (Is_True);

  procedure Is_True (B : Boolean) is
  begin
    if not B then
      raise Program_Error;
    end if;
  end;

begin
  R := (Az => 1.1, El => 2.2);
  Is_True (R.Az'Valid);
  R := (Az => 3.3, El => 4.4);
  Is_True (R.Az'Valid);
end;

Re: [PATCH] Fix PR tree-optimization/108199

[Richard Biener]

On Wed, Jan 11, 2023 at 11:00 AM Eric Botcazou via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
> Hi,
>
> this fixes the problematic interaction between bitfields, unions, SSO and SRA.
>
> Tested on x86-64/Linux and SPARC/Solaris, OK for all active branches?

OK.

Thanks,
Richard.

>
> 2023-01-11  Eric Botcazou  <ebotcazou@adacore.com>
>             Andreas Krebbel  <krebbel@linux.ibm.com>
>
>         PR tree-optimization/108199
>         * tree-sra.cc (sra_modify_expr): Deal with reverse storage order
>         for bit-field references.
>
>
> 2023-01-11  Eric Botcazou  <ebotcazou@adacore.com>
>
>         * gcc.dg/sso-17.c: New test.
>
> --
> Eric Botcazou