From: Alexandre Oliva <oliva@adacore.com>
Date: Mon, 11 Dec 2023 18:09:13 +0000 (-0300)
Subject: strub: add note on attribute access
X-Git-Tag: basepoints/gcc-15~3713
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=e4fc59e0d50cd3d2bb3a004fff135f5955621d01;p=thirdparty%2Fgcc.git

strub: add note on attribute access

Document why attribute access doesn't need the same treatment as fn
spec, and check that the assumption behind it holds.


for  gcc/ChangeLog

	* ipa-strub.cc (pass_ipa_strub::execute): Check that we don't
	add indirection to pointer parameters, and document attribute
	access non-interactions.
---

diff --git a/gcc/ipa-strub.cc b/gcc/ipa-strub.cc
index 2afb7a455751..8ec6824e8a80 100644
--- a/gcc/ipa-strub.cc
+++ b/gcc/ipa-strub.cc
@@ -2889,6 +2889,13 @@ pass_ipa_strub::execute (function *)
 		&& (tree_to_uhwi (TYPE_SIZE_UNIT (TREE_TYPE (nparm)))
 		    <= 4 * UNITS_PER_WORD))))
 	{
+	  /* No point in indirecting pointer types.  Presumably they
+	     won't ever pass the size-based test above, but check the
+	     assumption here, because getting this wrong would mess
+	     with attribute access and possibly others.  We deal with
+	     fn spec below.  */
+	  gcc_checking_assert (!POINTER_TYPE_P (TREE_TYPE (nparm)));
+
 	  indirect_nparms.add (nparm);
 
 	  /* ??? Is there any case in which it is not safe to suggest the parms
@@ -2976,7 +2983,9 @@ pass_ipa_strub::execute (function *)
 		}
 	    }
 
-	/* ??? Maybe we could adjust it instead.  */
+	/* ??? Maybe we could adjust it instead.  Note we don't need
+	   to mess with attribute access: pointer-typed parameters are
+	   not modified, so they can remain unchanged.  */
 	if (drop_fnspec)
 	  remove_named_attribute_unsharing ("fn spec",
 					    &TYPE_ATTRIBUTES (nftype));