[Ada] Fix PR bootstrap/109510

[Ada] Fix PR bootstrap/109510

[Eric Botcazou]

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This is the build failure of the Ada runtime for Aarch64 targets.  The Aarch64 
back-end now asserts that the main variant of scalar types has TYPE_USER_ALIGN 
cleared, and that's not the case for scalar types declared with a confirming 
alignment clause in Ada.

Tested on Aarch64/Linux by Richard S. (thanks!) and on x86-64/Linux by me, and 
applied on the mainline.


2023-04-14  Eric Botcazou  <ebotcazou@adacore.com>

	PR bootstrap/109510
	* gcc-interface/decl.cc (gnat_to_gnu_entity) <types>: Reset align
	to zero if its value is equal to TYPE_ALIGN and the type is scalar.
	Set TYPE_USER_ALIGN on the type only if align is positive.

-- 
Eric Botcazou

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diff --git a/gcc/ada/gcc-interface/decl.cc b/gcc/ada/gcc-interface/decl.cc
index d24adf33601..851a6745f77 100644
--- a/gcc/ada/gcc-interface/decl.cc
+++ b/gcc/ada/gcc-interface/decl.cc
@@ -4364,13 +4364,17 @@ gnat_to_gnu_entity (Entity_Id gnat_entity, tree gnu_expr, bool definition)
       /* If the alignment has not already been processed and this is not
 	 an unconstrained array type, see if an alignment is specified.
 	 If not, we pick a default alignment for atomic objects.  */
-      if (align != 0 || TREE_CODE (gnu_type) == UNCONSTRAINED_ARRAY_TYPE)
+      if (align > 0 || TREE_CODE (gnu_type) == UNCONSTRAINED_ARRAY_TYPE)
 	;
       else if (Known_Alignment (gnat_entity))
 	{
 	  align = validate_alignment (Alignment (gnat_entity), gnat_entity,
 				      TYPE_ALIGN (gnu_type));
 
+	  /* Treat confirming clauses on scalar types like the default.  */
+	  if (align == TYPE_ALIGN (gnu_type) && !AGGREGATE_TYPE_P (gnu_type))
+	    align = 0;
+
 	  /* Warn on suspiciously large alignments.  This should catch
 	     errors about the (alignment,byte)/(size,bit) discrepancy.  */
 	  if (align > BIGGEST_ALIGNMENT && Has_Alignment_Clause (gnat_entity))
@@ -4666,7 +4670,7 @@ gnat_to_gnu_entity (Entity_Id gnat_entity, tree gnu_expr, bool definition)
 	    TYPE_BY_REFERENCE_P (gnu_type) = 1;
 
 	  /* Record whether an alignment clause was specified.  */
-	  if (Present (Alignment_Clause (gnat_entity)))
+	  if (align > 0 && Present (Alignment_Clause (gnat_entity)))
 	    TYPE_USER_ALIGN (gnu_type) = 1;
 
 	  /* Record whether a pragma Universal_Aliasing was specified.  */

Re: [Ada] Fix PR bootstrap/109510

[Eric Botcazou]

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> Tested on Aarch64/Linux by Richard S. (thanks!) and on x86-64/Linux by me,
> and applied on the mainline.

It turns out that it slightly broke the x86/Linux compiler, which is not yet 
an acceptable trade-off.  Adjusted like this, tested on x86[_64]/Linux, this 
should not change anything for Aarch64 in particular.


	PR bootstrap/109510
	* gcc-interface/decl.cc (gnat_to_gnu_entity) <types>: Do not reset
	align to zero in any case.  Set TYPE_USER_ALIGN on the type only if
	it is an aggregate type, or else a type whose default alignment is
	specifically capped on selected platforms.

-- 
Eric Botcazou

[-- Attachment #2: p.diff --]
[-- Type: text/x-patch, Size: 2407 bytes --]

diff --git a/gcc/ada/gcc-interface/decl.cc b/gcc/ada/gcc-interface/decl.cc
index 851a6745f77..20f43de9ea9 100644
--- a/gcc/ada/gcc-interface/decl.cc
+++ b/gcc/ada/gcc-interface/decl.cc
@@ -4371,10 +4371,6 @@ gnat_to_gnu_entity (Entity_Id gnat_entity, tree gnu_expr, bool definition)
 	  align = validate_alignment (Alignment (gnat_entity), gnat_entity,
 				      TYPE_ALIGN (gnu_type));
 
-	  /* Treat confirming clauses on scalar types like the default.  */
-	  if (align == TYPE_ALIGN (gnu_type) && !AGGREGATE_TYPE_P (gnu_type))
-	    align = 0;
-
 	  /* Warn on suspiciously large alignments.  This should catch
 	     errors about the (alignment,byte)/(size,bit) discrepancy.  */
 	  if (align > BIGGEST_ALIGNMENT && Has_Alignment_Clause (gnat_entity))
@@ -4657,6 +4653,8 @@ gnat_to_gnu_entity (Entity_Id gnat_entity, tree gnu_expr, bool definition)
       /* If this is not an unconstrained array type, set some flags.  */
       if (TREE_CODE (gnu_type) != UNCONSTRAINED_ARRAY_TYPE)
 	{
+	  bool align_clause;
+
 	  /* Record the property that objects of tagged types are guaranteed to
 	     be properly aligned.  This is necessary because conversions to the
 	     class-wide type are translated into conversions to the root type,
@@ -4669,8 +4667,20 @@ gnat_to_gnu_entity (Entity_Id gnat_entity, tree gnu_expr, bool definition)
 	  if (is_by_ref && !VOID_TYPE_P (gnu_type))
 	    TYPE_BY_REFERENCE_P (gnu_type) = 1;
 
-	  /* Record whether an alignment clause was specified.  */
-	  if (align > 0 && Present (Alignment_Clause (gnat_entity)))
+	  /* Record whether an alignment clause was specified.  At this point
+	     scalar types with a non-confirming clause have been wrapped into
+	     a record type, so only scalar types with a confirming clause are
+	     left untouched; we do not set the flag on them except if they are
+	     types whose default alignment is specifically capped in order not
+	     to lose the specified alignment.  */
+	  if ((AGGREGATE_TYPE_P (gnu_type)
+	       && Present (Alignment_Clause (gnat_entity)))
+	      || (double_float_alignment > 0
+		  && is_double_float_or_array (gnat_entity, &align_clause)
+		  && align_clause)
+	      || (double_scalar_alignment > 0
+		  && is_double_scalar_or_array (gnat_entity, &align_clause)
+		  && align_clause))
 	    TYPE_USER_ALIGN (gnu_type) = 1;
 
 	  /* Record whether a pragma Universal_Aliasing was specified.  */