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[PATCH] Fix up go regressions caused by my recent switchconv changes (PR go/91617)


Apparently my recent tree-{cfg,switch-conversion}.c changes broke a bunch of
go tests.
The problem is that range_check_type actually doesn't guarantee an unsigned
type; it forces integer type for enum/bool (that was what was really needed
to fix the PR), and for integer types that don't wrap forces unsigned type
(and then verifies the wrap-around).  Seems go uses -fwrapv by default
and we got thus signed types from it.  That is fine if we emit the
x >= low && x < high range tests as x - low >= 0 && x - low < high - low,
but we actually don't emit the >= 0 check and so we do need an unsigned
type.  The other uses of range_check_type also eventually also call
unsigned_type_for, e.g.
  etype = range_check_type (etype);
  if (etype == NULL_TREE)
    return NULL_TREE;
  if (POINTER_TYPE_P (etype))
    etype = unsigned_type_for (etype);
and in the recursion then because low is 0:
      if (! TYPE_UNSIGNED (etype))          
          etype = unsigned_type_for (etype);
          high = fold_convert_loc (loc, etype, high);
          exp = fold_convert_loc (loc, etype, exp);
Similarly match.pd:
        tree etype = range_check_type (TREE_TYPE (@0));
        if (etype)
            if (! TYPE_UNSIGNED (etype))
              etype = unsigned_type_for (etype);
So, the following patch calls unsigned_type_for on the range_check_type

Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

2019-08-31  Jakub Jelinek  <>

	PR go/91617
	* tree-cfg.c (generate_range_test): Call unsigned_type_for on
	the range_check_type result.
	* tree-switch-conversion.c (switch_conversion::build_one_array,
	bit_test_cluster::emit): Likewise.

--- gcc/tree-cfg.c.jj	2019-08-31 12:09:09.135153318 +0200
+++ gcc/tree-cfg.c	2019-08-31 12:48:06.259939680 +0200
@@ -9222,6 +9222,7 @@ generate_range_test (basic_block bb, tre
   tree type = TREE_TYPE (index);
   tree utype = range_check_type (type);
+  utype = unsigned_type_for (utype);
   low = fold_convert (utype, low);
   high = fold_convert (utype, high);
--- gcc/tree-switch-conversion.c.jj	2019-08-31 12:09:09.129153406 +0200
+++ gcc/tree-switch-conversion.c	2019-08-31 12:48:28.340617487 +0200
@@ -616,6 +616,7 @@ switch_conversion::build_one_array (int
       /* We must use type of constructor values.  */
       gimple_seq seq = NULL;
+      type = unsigned_type_for (type);
       tree tmp = gimple_convert (&seq, type, m_index_expr);
       tree tmp2 = gimple_build (&seq, MULT_EXPR, type,
 				wide_int_to_tree (type, coeff_a), tmp);
@@ -1486,6 +1487,7 @@ bit_test_cluster::emit (tree index_expr,
   unsigned int count;
   tree unsigned_index_type = range_check_type (index_type);
+  unsigned_index_type = unsigned_type_for (unsigned_index_type);
   gimple_stmt_iterator gsi;
   gassign *shift_stmt;


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