[PATCH] [strub] improve handling of indirected volatile parms [PR112938]

[Alexandre Oliva <oliva@adacore.com>]

The earlier patch for PR112938 arranged for volatile parms to be made
indirect in internal strub wrapped bodies.

The first problem that remained, more evident, was that the indirected
parameter remained volatile, despite the indirection, but it wasn't
regimplified, so indirecting it was malformed gimple.

Regimplifying turned out not to be needed.  The best course of action
was to drop the volatility from the by-reference parm, that was being
unexpectedly inherited from the original volatile parm.

That exposed another problem: the dereferences would then lose their
volatile status, so we had to bring volatile back to them.

Regstrapped on x86_64-linux-gnu.  Ok to install?


for  gcc/ChangeLog

	PR middle-end/112938
	* ipa-strub.cc (pass_ipa_strub::execute): Drop volatility from
	indirected parm.
	(maybe_make_indirect): Restore volatility in dereferences.

for  gcc/testsuite/ChangeLog

	PR middle-end/112938
	* g++.dg/strub-internal-pr112938.cc: New.
---
 gcc/ipa-strub.cc                                |    7 +++++++
 gcc/testsuite/g++.dg/strub-internal-pr112938.cc |   12 ++++++++++++
 2 files changed, 19 insertions(+)
 create mode 100644 gcc/testsuite/g++.dg/strub-internal-pr112938.cc

diff --git a/gcc/ipa-strub.cc b/gcc/ipa-strub.cc
index dff94222351ad..8fa7bdf530023 100644
--- a/gcc/ipa-strub.cc
+++ b/gcc/ipa-strub.cc
@@ -1940,6 +1940,9 @@ maybe_make_indirect (indirect_parms_t &indirect_parms, tree op, int *rec)
 			  TREE_TYPE (TREE_TYPE (op)),
 			  op,
 			  build_int_cst (TREE_TYPE (op), 0));
+	  if (TYPE_VOLATILE (TREE_TYPE (TREE_TYPE (op)))
+	      && !TREE_THIS_VOLATILE (ret))
+	    TREE_SIDE_EFFECTS (ret) = TREE_THIS_VOLATILE (ret) = 1;
 	  return ret;
 	}
     }
@@ -2894,6 +2897,10 @@ pass_ipa_strub::execute (function *)
 	     probably drop the TREE_ADDRESSABLE and keep the TRUE.  */
 	  tree ref_type = build_ref_type_for (nparm);
 
+	  if (TREE_THIS_VOLATILE (nparm)
+	      && TYPE_VOLATILE (TREE_TYPE (nparm))
+	      && !TYPE_VOLATILE (ref_type))
+	    TREE_SIDE_EFFECTS (nparm) = TREE_THIS_VOLATILE (nparm) = 0;
 	  DECL_ARG_TYPE (nparm) = TREE_TYPE (nparm) = ref_type;
 	  relayout_decl (nparm);
 	  TREE_ADDRESSABLE (nparm) = 0;
diff --git a/gcc/testsuite/g++.dg/strub-internal-pr112938.cc b/gcc/testsuite/g++.dg/strub-internal-pr112938.cc
new file mode 100644
index 0000000000000..5a74becc2697e
--- /dev/null
+++ b/gcc/testsuite/g++.dg/strub-internal-pr112938.cc
@@ -0,0 +1,12 @@
+/* { dg-do compile } */
+/* { dg-options "-fdump-tree-optimized -O2" } */
+/* { dg-require-effective-target strub } */
+
+bool __attribute__ ((__strub__ ("internal")))
+f(bool i, volatile bool j)
+{
+  return (i ^ j) == j;
+}
+
+/* Check for two dereferences of the indirected volatile j parm.  */
+/* { dg-final { scan-tree-dump-times {={v} \*j_[0-9][0-9]*(D)} 2 "optimized" } } */

-- 
Alexandre Oliva, happy hacker            https://FSFLA.org/blogs/lxo/
   Free Software Activist                   GNU Toolchain Engineer
More tolerance and less prejudice are key for inclusion and diversity
Excluding neuro-others for not behaving ""normal"" is *not* inclusive