[Bug target/88234] UBsan and runtime error: signed integer overflow using unsigned vector

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88234

--- Comment #7 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
--- gcc/config/rs6000/rs6000.c.jj       2018-11-27 16:40:23.821758250 +0100
+++ gcc/config/rs6000/rs6000.c  2018-11-28 15:15:08.254736153 +0100
@@ -15328,6 +15328,7 @@ rs6000_gimple_fold_builtin (gimple_stmt_
   enum rs6000_builtins fn_code
     = (enum rs6000_builtins) DECL_FUNCTION_CODE (fndecl);
   tree arg0, arg1, lhs, temp;
+  enum tree_code bcode;
   gimple *g;

   size_t uns_fncode = (size_t) fn_code;
@@ -15366,10 +15367,32 @@ rs6000_gimple_fold_builtin (gimple_stmt_
     case P8V_BUILTIN_VADDUDM:
     case ALTIVEC_BUILTIN_VADDFP:
     case VSX_BUILTIN_XVADDDP:
+      bcode = PLUS_EXPR;
+    do_binary:
       arg0 = gimple_call_arg (stmt, 0);
       arg1 = gimple_call_arg (stmt, 1);
       lhs = gimple_call_lhs (stmt);
-      g = gimple_build_assign (lhs, PLUS_EXPR, arg0, arg1);
+      if (INTEGRAL_TYPE_P (TREE_TYPE (TREE_TYPE (lhs)))
+         && !TYPE_OVERFLOW_WRAPS (TREE_TYPE (TREE_TYPE (lhs))))
+       {
+         /* Ensure the binary operation is performed in a type
+            that wraps if it is integral type.  */
+         gimple_seq stmts = NULL;
+         tree type = unsigned_type_for (TREE_TYPE (lhs));
+         tree uarg0 = gimple_build (&stmts, VIEW_CONVERT_EXPR,
+                                    type, arg0);
+         tree uarg1 = gimple_build (&stmts, VIEW_CONVERT_EXPR,
+                                    type, arg1);
+         tree res = gimple_build (&stmts, gimple_location (stmt), bcode,
+                                  type, uarg0, uarg1);
+         gsi_insert_seq_before (gsi, stmts, GSI_SAME_STMT);
+         g = gimple_build_assign (lhs, VIEW_CONVERT_EXPR,
+                                  build1 (VIEW_CONVERT_EXPR,
+                                          TREE_TYPE (lhs), res));
+         gsi_replace (gsi, g, true);
+         return true;
+       }
+      g = gimple_build_assign (lhs, bcode, arg0, arg1);
       gimple_set_location (g, gimple_location (stmt));
       gsi_replace (gsi, g, true);
       return true;
@@ -15381,13 +15404,8 @@ rs6000_gimple_fold_builtin (gimple_stmt_
     case P8V_BUILTIN_VSUBUDM:
     case ALTIVEC_BUILTIN_VSUBFP:
     case VSX_BUILTIN_XVSUBDP:
-      arg0 = gimple_call_arg (stmt, 0);
-      arg1 = gimple_call_arg (stmt, 1);
-      lhs = gimple_call_lhs (stmt);
-      g = gimple_build_assign (lhs, MINUS_EXPR, arg0, arg1);
-      gimple_set_location (g, gimple_location (stmt));
-      gsi_replace (gsi, g, true);
-      return true;
+      bcode = MINUS_EXPR;
+      goto do_binary;
     case VSX_BUILTIN_XVMULSP:
     case VSX_BUILTIN_XVMULDP:
       arg0 = gimple_call_arg (stmt, 0);

handles this, but I'm not sure if it is correct for all the builtins that can
show up and if it isn't needed for some other builtins (e.g. some
multiplications too).