sccvn: Fix handling of POINTER_PLUS_EXPR in memset offset [PR93582]

> > where POINTER_PLUS_EXPR last operand has sizetype type, thus unsigned,
> > and in the testcase gimple_assign_rhs2 (def) is thus 0xf000000000000001ULL
> > which multiplied by 8 doesn't fit into signed HWI.  If it would be treated
> > as signed offset instead, it would fit (-0xfffffffffffffffLL, multiplied
> > by 8 is -0x7ffffffffffffff8LL).  Unfortunately with the poly_int obfuscation
> > I'm not sure how to convert it from unsigned to signed poly_int.
>
> mem_ref_offset provides a boiler-plate for this:
>
> poly_offset_int::from (wi::to_poly_wide (TREE_OPERAND (t, 1)), SIGNED);

Thanks, that seems to work.
The test now works on both big-endian and little-endian.

2020-03-05  Richard Biener  <rguenther@suse.de>
	    Jakub Jelinek  <jakub@redhat.com>

	PR tree-optimization/93582
	* tree-ssa-sccvn.c (vn_reference_lookup_3): Treat POINTER_PLUS_EXPR
	last operand as signed when looking for memset offset.  Formatting
	fix.

	* gcc.dg/tree-ssa/pr93582-11.c: New test.

Co-authored-by: Richard Biener <rguenther@suse.de>

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 5b2e4a8..897c598 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,11 @@
+2020-03-05  Richard Biener  <rguenther@suse.de>
+           Jakub Jelinek  <jakub@redhat.com>
+
+       PR tree-optimization/93582
+       * tree-ssa-sccvn.c (vn_reference_lookup_3): Treat POINTER_PLUS_EXPR
+       last operand as signed when looking for memset offset.  Formatting
+       fix.
+
 2020-03-04  Andrew Pinski  <apinski@marvell.com>
 
        PR bootstrap/93962

diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 95c8710..d4e7a3a 100644 (file)
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2020-03-05  Jakub Jelinek  <jakub@redhat.com>
+
+       PR tree-optimization/93582
+       * gcc.dg/tree-ssa/pr93582-11.c: New test.
+
 2020-03-04  Martin Sebor  <msebor@redhat.com>
 
        PR c++/90938

diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr93582-11.c b/gcc/testsuite/gcc.dg/tree-ssa/pr93582-11.c
new file mode 100644 (file)
index 0000000..9ff400e
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/pr93582-11.c
@@ -0,0 +1,16 @@
+/* PR tree-optimization/93582 */
+/* { dg-do compile { target lp64 } } */
+/* { dg-options "-O2 -fdump-tree-fre1" } */
+/* { dg-final { scan-tree-dump "return 9223372036854775806;" "fre1" } } */
+
+union U { struct A { unsigned long long a : 1, b : 62, c : 1; } a; unsigned long long i; };
+
+unsigned long long
+foo (char *p)
+{
+  __builtin_memset (p - 0xfffffffffffffffULL, 0, 0xffffffffffffffeULL);
+  __builtin_memset (p + 1, 0, 0xffffffffffffffeULL);
+  union U *q = (union U *) (void *) (p - 4);
+  q->a.b = -1;
+  return q->i;
+}

diff --git a/gcc/tree-ssa-sccvn.c b/gcc/tree-ssa-sccvn.c
index 9ea30ef..b7174cd 100644 (file)
--- a/gcc/tree-ssa-sccvn.c
+++ b/gcc/tree-ssa-sccvn.c
@@ -2656,7 +2656,8 @@ vn_reference_lookup_3 (ao_ref *ref, tree vuse, void *data_,
        {
          poly_int64 soff;
          if (TREE_CODE (base) != MEM_REF
-             || !(mem_ref_offset (base) << LOG2_BITS_PER_UNIT).to_shwi (&soff))
+             || !(mem_ref_offset (base)
+                  << LOG2_BITS_PER_UNIT).to_shwi (&soff))
            return (void *)-1;
          offset += soff;
          offset2 = 0;
@@ -2666,10 +2667,13 @@ vn_reference_lookup_3 (ao_ref *ref, tree vuse, void *data_,
              if (is_gimple_assign (def)
                  && gimple_assign_rhs_code (def) == POINTER_PLUS_EXPR
                  && gimple_assign_rhs1 (def) == TREE_OPERAND (base, 0)
-                 && poly_int_tree_p (gimple_assign_rhs2 (def))
-                 && (wi::to_poly_offset (gimple_assign_rhs2 (def))
-                     << LOG2_BITS_PER_UNIT).to_shwi (&offset2))
+                 && poly_int_tree_p (gimple_assign_rhs2 (def)))
                {
+                 tree rhs2 = gimple_assign_rhs2 (def);
+                 if (!(poly_offset_int::from (wi::to_poly_wide (rhs2),
+                                              SIGNED)
+                       << LOG2_BITS_PER_UNIT).to_shwi (&offset2))
+                   return (void *)-1;
                  ref2 = gimple_assign_rhs1 (def);
                  if (TREE_CODE (ref2) == SSA_NAME)
                    ref2 = SSA_VAL (ref2);