[PATCH] Fix wrong array type conversion with different storage order

[Eric Botcazou via Gcc-patches]

Hi,

when two arrays of scalars have a different storage order in Ada, the
front-end makes sure that the conversion is performed component-wise
so that each component can be reversed.  So it's a little bit counter
productive that the ldist pass performs the opposite transformation
and synthesizes a memcpy/memmove in this case.

Tested on x86-64/Linux, OK for the mainline?


2022-11-22  Eric Botcazou  <ebotca...@adacore.com>

        * tree-loop-distribution.cc (loop_distribution::classify_builtin_ldst):
        Bail out if source and destination do not have the same storage order.


2022-11-22  Eric Botcazou  <ebotca...@adacore.com>

        * gnat.dg/sso18.adb: New test.

-- 
Eric Botcazou
diff --git a/gcc/tree-loop-distribution.cc b/gcc/tree-loop-distribution.cc
index ed3dd73e1a9..15ae2410861 100644
--- a/gcc/tree-loop-distribution.cc
+++ b/gcc/tree-loop-distribution.cc
@@ -1790,10 +1790,15 @@ loop_distribution::classify_builtin_ldst (loop_p loop, struct graph *rdg,
   if (res != 2)
     return;
 
-  /* They much have the same access size.  */
+  /* They must have the same access size.  */
   if (!operand_equal_p (size, src_size, 0))
     return;
 
+  /* They must have the same storage order.  */
+  if (reverse_storage_order_for_component_p (DR_REF (dst_dr))
+      != reverse_storage_order_for_component_p (DR_REF (src_dr)))
+    return;
+
   /* Load and store in loop nest must access memory in the same way, i.e,
      their must have the same steps in each loop of the nest.  */
   if (dst_steps.length () != src_steps.length ())

--  { dg-do run }
--  { dg-options "-O2" }

with System;

procedure SSO18 is

  type Arr is array (1..32) of Short_Integer;
  type Rev_Arr is array (1..32) of Short_Integer
    with Scalar_Storage_Order => System.High_Order_First;
  C : constant Arr := (others => 16);
  RA : Rev_Arr;
  A  : Arr;

begin
  RA := Rev_Arr(C);
  A := Arr (RA);
  if A /= C or else RA(1) /= 16 then
     raise Program_Error;
  end if;
end;