[gcc(refs/vendors/ARM/heads/morello)] Allow capability->non-capability pointer conversions

[gcc(refs/vendors/ARM/heads/morello)] Allow capability->non-capability pointer conversions

[Matthew Malcomson]

https://gcc.gnu.org/g:2912ef897f2684d69ee05eca50a42ac2e61749ab

commit 2912ef897f2684d69ee05eca50a42ac2e61749ab
Author: Richard Sandiford <richard.sandiford@arm.com>
Date:   Thu Apr 7 16:14:11 2022 +0100

    Allow capability->non-capability pointer conversions
    
    This patch allows a capability pointer to be converted to a
    non-capability pointer, dropping the metadata in the process.
    Such conversions can only occur for hybrid capabilities;
    in other cases, all pointers are capabilities or all pointers
    are not.
    
    Co-authored-by: Matthew Malcolmson <matthew.malcomson@arm.com>

Diff:
---
 gcc/testsuite/gcc.target/aarch64/morello/pointer-arith-3.c |  9 +++++++++
 gcc/tree.h                                                 | 14 +++++++-------
 2 files changed, 16 insertions(+), 7 deletions(-)

diff --git a/gcc/testsuite/gcc.target/aarch64/morello/pointer-arith-3.c b/gcc/testsuite/gcc.target/aarch64/morello/pointer-arith-3.c
new file mode 100644
index 00000000000..59d92287ba6
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/morello/pointer-arith-3.c
@@ -0,0 +1,9 @@
+/* { dg-do assemble } */
+/* { dg-additional-options "-save-temps" } */
+/* { dg-final { check-function-bodies "**" ""  { {-O[123s]} } } } */
+
+/*
+** foo:
+**	ret
+*/
+int *foo(int *__capability x) { return (int *)x; }
diff --git a/gcc/tree.h b/gcc/tree.h
index e5706f13340..0085afb091f 100644
--- a/gcc/tree.h
+++ b/gcc/tree.h
@@ -6426,15 +6426,15 @@ capability_args_valid (const_tree type,
 		|| (TYPE_MODE (type) != TYPE_MODE (rhs_type))))
 	  return false;
 
-	/* Any conversions *from* a capability type must be either to
-	   another capability type of the same machine mode, to an
-	   integral type with precision less than or equal to that of
-	   the value of a given capability, or to void_type_node.  The
-	   first case is handled by the above clause, while we handle
-	   the other cases here.  */
+	/* Any conversions *from* a capability type must be either to another
+	   capability type of the same machine mode, to an integral type or
+	   non-capability pointer type with a precision less than or equal to
+	   the precision of the value of a given capability, or to
+	   void_type_node.  The first case is handled by the above clause,
+	   while we handle the other cases here.  */
 	if (capability_type_p (rhs_type)
 	    && !capability_type_p (type)
-	    && (!INTEGRAL_TYPE_P (type)
+	    && (!(INTEGRAL_TYPE_P (type) || POINTER_TYPE_P (type))
 		|| (TYPE_PRECISION (type) > TYPE_NONCAP_PRECISION (rhs_type)))
 	    && type != void_type_node)
 	  return false;