tree-optimization/104064 - UBSAN issue in vect dataref analysis

Since we order DRs after DR_INIT we know the difference will be
positive and thus can avoid signed overflow issues by using
unsigned arithmetic to produce the known unsigned result.

2022-01-18  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/104064
	* tree-vect-data-refs.cc (vect_analyze_data_ref_accesses): Check
	DR_INIT fits in a signed HWI, represent the difference from the
	first DR in unsigned.

diff --git a/gcc/tree-vect-data-refs.cc b/gcc/tree-vect-data-refs.cc
index dd20ed974af3cee00ca215a15945620ddb8881a7..09223baf71890b34ebed004560fafbd60691530d 100644 (file)
--- a/gcc/tree-vect-data-refs.cc
+++ b/gcc/tree-vect-data-refs.cc
@@ -3172,8 +3172,8 @@ vect_analyze_data_ref_accesses (vec_info *vinfo,
            break;
 
          /* Check that the DR_INITs are compile-time constants.  */
-         if (TREE_CODE (DR_INIT (dra)) != INTEGER_CST
-             || TREE_CODE (DR_INIT (drb)) != INTEGER_CST)
+         if (!tree_fits_shwi_p (DR_INIT (dra))
+             || !tree_fits_shwi_p (DR_INIT (drb)))
            break;
 
          /* Different .GOMP_SIMD_LANE calls still give the same lane,
@@ -3203,15 +3203,18 @@ vect_analyze_data_ref_accesses (vec_info *vinfo,
            {
              /* If init_b == init_a + the size of the type * k, we have an
                 interleaving, and DRA is accessed before DRB.  */
-             HOST_WIDE_INT type_size_a = tree_to_uhwi (sza);
+             unsigned HOST_WIDE_INT type_size_a = tree_to_uhwi (sza);
              if (type_size_a == 0
-                 || (init_b - init_a) % type_size_a != 0)
+                 || (((unsigned HOST_WIDE_INT)init_b - init_a)
+                     % type_size_a != 0))
                break;
 
              /* If we have a store, the accesses are adjacent.  This splits
                 groups into chunks we support (we don't support vectorization
                 of stores with gaps).  */
-             if (!DR_IS_READ (dra) && init_b - init_prev != type_size_a)
+             if (!DR_IS_READ (dra)
+                 && (((unsigned HOST_WIDE_INT)init_b - init_prev)
+                     != type_size_a))
                break;
 
              /* If the step (if not zero or non-constant) is smaller than the
@@ -3222,7 +3225,7 @@ vect_analyze_data_ref_accesses (vec_info *vinfo,
                  unsigned HOST_WIDE_INT step
                    = absu_hwi (tree_to_shwi (DR_STEP (dra)));
                  if (step != 0
-                     && step <= (unsigned HOST_WIDE_INT)(init_b - init_a))
+                     && step <= ((unsigned HOST_WIDE_INT)init_b - init_a))
                    break;
                }
            }