[gcc r11-9332] ranger: Fix up fold_using_range::range_of_address [PR103255]

[Jakub Jelinek <jakub@gcc.gnu.org>]

https://gcc.gnu.org/g:a6219e8e0719b14f474b0dcaa7bde2f4e57474f9

commit r11-9332-ga6219e8e0719b14f474b0dcaa7bde2f4e57474f9
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Wed Nov 17 13:45:53 2021 +0100

    ranger: Fix up fold_using_range::range_of_address [PR103255]
    
    If on &base->member the offset isn't constant or isn't zero and
    -fdelete-null-pointer-checks and not -fwrapv-pointer and base has a range
    that doesn't include NULL, we return the range of the base.
    Usually it isn't a big deal, because for most pointers we just use
    varying, range_zero and range_nonzero ranges and nothing beyond that,
    but if a pointer is initialized from a constant, we actually track the
    exact range and in that case this causes miscompilation.
    As discussed on IRC, I think doing something like:
                  offset_int off2;
                  if (off_cst && off.is_constant (&off2))
                    {
                      tree cst = wide_int_to_tree (sizetype, off2 / BITS_PER_UNIT);
                      // adjust range r with POINTER_PLUS_EXPR cst
                      if (!range_includes_zero_p (&r))
                        return true;
                    }
                  // Fallback
                  r = range_nonzero (TREE_TYPE (gimple_assign_rhs1 (stmt)));
                  return true;
    could work, given that most of the pointer ranges are just the simple ones
    perhaps it is too much for little benefit.
    
    2021-11-17  Jakub Jelinek  <jakub@redhat.com>
    
            PR tree-optimization/103255
            * gimple-range.cc (fold_using_range::range_of_address): Return
            range_nonzero rather than unadjusted base's range.  Formatting fixes.
    
            * gcc.c-torture/execute/pr103255.c: New test.
    
    (cherry picked from commit c39cb6bf835ca12e590eaa6f90222e51be207c50)

Diff:
---
 gcc/gimple-range.cc                            | 16 ++++++----
 gcc/testsuite/gcc.c-torture/execute/pr103255.c | 41 ++++++++++++++++++++++++++
 2 files changed, 52 insertions(+), 5 deletions(-)

diff --git a/gcc/gimple-range.cc b/gcc/gimple-range.cc
index fd7fa5e3dbb..f71ee6663fd 100644
--- a/gcc/gimple-range.cc
+++ b/gcc/gimple-range.cc
@@ -491,14 +491,20 @@ gimple_ranger::range_of_address (irange &r, gimple *stmt)
 	}
       /* If &X->a is equal to X, the range of X is the result.  */
       if (off_cst && known_eq (off, 0))
-	  return true;
+	return true;
       else if (flag_delete_null_pointer_checks
 	       && !TYPE_OVERFLOW_WRAPS (TREE_TYPE (expr)))
 	{
-	 /* For -fdelete-null-pointer-checks -fno-wrapv-pointer we don't
-	 allow going from non-NULL pointer to NULL.  */
-	   if(!range_includes_zero_p (&r))
-	    return true;
+	  /* For -fdelete-null-pointer-checks -fno-wrapv-pointer we don't
+	     allow going from non-NULL pointer to NULL.  */
+	  if (!range_includes_zero_p (&r))
+	    {
+	      /* We could here instead adjust r by off >> LOG2_BITS_PER_UNIT
+		 using POINTER_PLUS_EXPR if off_cst and just fall back to
+		 this.  */
+	      r = range_nonzero (TREE_TYPE (gimple_assign_rhs1 (stmt)));
+	      return true;
+	    }
 	}
       /* If MEM_REF has a "positive" offset, consider it non-NULL
 	 always, for -fdelete-null-pointer-checks also "negative"
diff --git a/gcc/testsuite/gcc.c-torture/execute/pr103255.c b/gcc/testsuite/gcc.c-torture/execute/pr103255.c
new file mode 100644
index 00000000000..d74b054252f
--- /dev/null
+++ b/gcc/testsuite/gcc.c-torture/execute/pr103255.c
@@ -0,0 +1,41 @@
+/* PR tree-optimization/103255 */
+
+struct H
+{
+  unsigned a;
+  unsigned b;
+  unsigned c;
+};
+
+#if __SIZEOF_POINTER__ >= 4
+#define ADDR 0x400000
+#else
+#define ADDR 0x4000
+#endif
+#define OFF 0x20
+
+int
+main ()
+{
+  struct H *h = 0;
+  unsigned long o;
+  volatile int t = 1;
+
+  for (o = OFF; o <= OFF; o += 0x1000)
+    {
+      struct H *u;
+      u = (struct H *) (ADDR + o);
+      if (t)
+	{
+	  h = u;
+	  break;
+	}
+    }
+
+  if (h == 0)
+    return 0;
+  unsigned *tt = &h->b;
+  if ((__SIZE_TYPE__) tt != (ADDR + OFF + __builtin_offsetof (struct H, b)))
+    __builtin_abort ();
+  return 0;
+}