alias: Perform offset arithmetics in poly_offset_int rather than poly_int64 [PR118819]

This PR is about ubsan error on the c - cx1 + cy1 evaluation in the first
hunk.

The following patch hopefully fixes that by doing the additions/subtractions
in poly_offset_int rather than poly_int64 and then converting back to poly_int64.
If it doesn't fit, -1 is returned (which means it is unknown if there is a conflict
or not).

2025-02-27  Jakub Jelinek  <jakub@redhat.com>

	PR middle-end/118819
	* alias.cc (memrefs_conflict_p): Perform arithmetics on c, xsize and
	ysize in poly_offset_int and return -1 if it is not representable in
	poly_int64.

diff --git a/gcc/alias.cc b/gcc/alias.cc
index 497c2ac0e33a60596170347b0486a07bd57fc18c..4f17664c15b3fc1a1ffa1f1bb99cae8aea5c90b8 100644 (file)
--- a/gcc/alias.cc
+++ b/gcc/alias.cc
@@ -2535,19 +2535,39 @@ memrefs_conflict_p (poly_int64 xsize, rtx x, poly_int64 ysize, rtx y,
            return memrefs_conflict_p (xsize, x1, ysize, y1, c);
          if (poly_int_rtx_p (x1, &cx1))
            {
+             poly_offset_int co = c;
+             co -= cx1;
              if (poly_int_rtx_p (y1, &cy1))
-               return memrefs_conflict_p (xsize, x0, ysize, y0,
-                                          c - cx1 + cy1);
+               {
+                 co += cy1;
+                 if (!co.to_shwi (&c))
+                   return -1;
+                 return memrefs_conflict_p (xsize, x0, ysize, y0, c);
+               }
+             else if (!co.to_shwi (&c))
+               return -1;
              else
-               return memrefs_conflict_p (xsize, x0, ysize, y, c - cx1);
+               return memrefs_conflict_p (xsize, x0, ysize, y, c);
            }
          else if (poly_int_rtx_p (y1, &cy1))
-           return memrefs_conflict_p (xsize, x, ysize, y0, c + cy1);
+           {
+             poly_offset_int co = c;
+             co += cy1;
+             if (!co.to_shwi (&c))
+               return -1;
+             return memrefs_conflict_p (xsize, x, ysize, y0, c);
+           }
 
          return -1;
        }
       else if (poly_int_rtx_p (x1, &cx1))
-       return memrefs_conflict_p (xsize, x0, ysize, y, c - cx1);
+       {
+         poly_offset_int co = c;
+         co -= cx1;
+         if (!co.to_shwi (&c))
+           return -1;
+         return memrefs_conflict_p (xsize, x0, ysize, y, c);
+       }
     }
   else if (GET_CODE (y) == PLUS)
     {
@@ -2563,7 +2583,13 @@ memrefs_conflict_p (poly_int64 xsize, rtx x, poly_int64 ysize, rtx y,
 
       poly_int64 cy1;
       if (poly_int_rtx_p (y1, &cy1))
-       return memrefs_conflict_p (xsize, x, ysize, y0, c + cy1);
+       {
+         poly_offset_int co = c;
+         co += cy1;
+         if (!co.to_shwi (&c))
+           return -1;
+         return memrefs_conflict_p (xsize, x, ysize, y0, c);
+       }
       else
        return -1;
     }
@@ -2616,8 +2642,16 @@ memrefs_conflict_p (poly_int64 xsize, rtx x, poly_int64 ysize, rtx y,
          if (maybe_gt (xsize, 0))
            xsize = -xsize;
          if (maybe_ne (xsize, 0))
-           xsize += sc + 1;
-         c -= sc + 1;
+           {
+             poly_offset_int xsizeo = xsize;
+             xsizeo += sc + 1;
+             if (!xsizeo.to_shwi (&xsize))
+               return -1;
+           }
+         poly_offset_int co = c;
+         co -= sc + 1;
+         if (!co.to_shwi (&c))
+           return -1;
          return memrefs_conflict_p (xsize, canon_rtx (XEXP (x, 0)),
                                     ysize, y, c);
        }
@@ -2631,8 +2665,16 @@ memrefs_conflict_p (poly_int64 xsize, rtx x, poly_int64 ysize, rtx y,
          if (maybe_gt (ysize, 0))
            ysize = -ysize;
          if (maybe_ne (ysize, 0))
-           ysize += sc + 1;
-         c += sc + 1;
+           {
+             poly_offset_int ysizeo = ysize;
+             ysizeo += sc + 1;
+             if (!ysizeo.to_shwi (&ysize))
+               return -1;
+           }
+         poly_offset_int co = c;
+         co += sc + 1;
+         if (!co.to_shwi (&c))
+           return -1;
          return memrefs_conflict_p (xsize, x,
                                     ysize, canon_rtx (XEXP (y, 0)), c);
        }
@@ -2643,7 +2685,11 @@ memrefs_conflict_p (poly_int64 xsize, rtx x, poly_int64 ysize, rtx y,
       poly_int64 cx, cy;
       if (poly_int_rtx_p (x, &cx) && poly_int_rtx_p (y, &cy))
        {
-         c += cy - cx;
+         poly_offset_int co = c;
+         co += cy;
+         co -= cx;
+         if (!co.to_shwi (&c))
+           return -1;
          return offset_overlap_p (c, xsize, ysize);
        }