[gcc r14-2783] tree-optimization/110799 - fix bug in code hoisting

[Richard Biener]

https://gcc.gnu.org/g:565e0e80660dac24e5193873ca07542b99cd8bc3

commit r14-2783-g565e0e80660dac24e5193873ca07542b99cd8bc3
Author: Richard Biener <rguenther@suse.de>
Date:   Wed Jul 26 09:28:10 2023 +0200

    tree-optimization/110799 - fix bug in code hoisting
    
    Code hoisting part of GIMPLE PRE failed to adjust the TBAA behavior
    of common loads in the case the alias set of the ref was the same
    but the base alias set was not.  It also failed to adjust the
    base behavior, assuming it would match.  The following plugs this
    hole.
    
            PR tree-optimization/110799
            * tree-ssa-pre.cc (compute_avail): More thoroughly match
            up TBAA behavior of redundant loads.
    
            * gcc.dg/torture/pr110799.c: New testcase.

Diff:
---
 gcc/testsuite/gcc.dg/torture/pr110799.c | 46 +++++++++++++++++++++++++++++++++
 gcc/tree-ssa-pre.cc                     | 15 +++++++----
 2 files changed, 56 insertions(+), 5 deletions(-)

diff --git a/gcc/testsuite/gcc.dg/torture/pr110799.c b/gcc/testsuite/gcc.dg/torture/pr110799.c
new file mode 100644
index 00000000000..53f06f079e1
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/pr110799.c
@@ -0,0 +1,46 @@
+/* { dg-do run { target { { *-*-linux* *-*-gnu* *-*-uclinux* } && mmap } } } */
+
+#include <unistd.h>
+#include <stdlib.h>
+#include <sys/mman.h>
+
+struct S {
+    int a;
+};
+struct M {
+    int a, b;
+};
+
+int __attribute__((noipa))
+f(struct S *p, int c, int d)
+{
+  int r;
+  if (c)
+    {
+      if (d)
+	r = p->a;
+      else
+	r = ((struct M*)p)->a;
+    }
+  else
+    r = ((struct M*)p)->b;
+  return r;
+}
+
+int main ()
+{
+  long pgsz = sysconf(_SC_PAGESIZE);
+  if (pgsz < sizeof (struct M))
+    return 0;
+  char *p = mmap ((void *) 0, 2 * pgsz, PROT_NONE, MAP_PRIVATE | MAP_ANONYMOUS,
+		  -1, 0);
+  if (p == MAP_FAILED)
+    return 0;
+  if (mprotect (p, pgsz, PROT_READ | PROT_WRITE))
+    return 0;
+  struct S *q = (struct S *)(p + pgsz) - 1;
+  q->a = 42;
+  if (f (q, 1, 1) != 42)
+    abort ();
+  return 0;
+}
diff --git a/gcc/tree-ssa-pre.cc b/gcc/tree-ssa-pre.cc
index e33c5ba80e2..0f2e458395c 100644
--- a/gcc/tree-ssa-pre.cc
+++ b/gcc/tree-ssa-pre.cc
@@ -4217,8 +4217,10 @@ compute_avail (function *fun)
 		      /* TBAA behavior is an obvious part so make sure
 		         that the hashtable one covers this as well
 			 by adjusting the ref alias set and its base.  */
-		      if (ref->set == set
-			  || alias_set_subset_of (set, ref->set))
+		      if ((ref->set == set
+			   || alias_set_subset_of (set, ref->set))
+			  && (ref->base_set == base_set
+			      || alias_set_subset_of (base_set, ref->base_set)))
 			;
 		      else if (ref1->opcode != ref2->opcode
 			       || (ref1->opcode != MEM_REF
@@ -4230,16 +4232,19 @@ compute_avail (function *fun)
 			  operands.release ();
 			  continue;
 			}
-		      else if (alias_set_subset_of (ref->set, set))
+		      else if (ref->set == set
+			       || alias_set_subset_of (ref->set, set))
 			{
+			  tree reft = reference_alias_ptr_type (rhs1);
 			  ref->set = set;
+			  ref->base_set = set;
 			  if (ref1->opcode == MEM_REF)
 			    ref1->op0
-			      = wide_int_to_tree (TREE_TYPE (ref2->op0),
+			      = wide_int_to_tree (reft,
 						  wi::to_wide (ref1->op0));
 			  else
 			    ref1->op2
-			      = wide_int_to_tree (TREE_TYPE (ref2->op2),
+			      = wide_int_to_tree (reft,
 						  wi::to_wide (ref1->op2));
 			}
 		      else