[patch] PR tree-optimization/96818 - cast label range to type of switch operand

Jakub Jelinek jakub@redhat.com
Mon Aug 31 08:38:54 GMT 2020


On Mon, Aug 31, 2020 at 10:33:20AM +0200, Richard Biener wrote:
> In any case type mismatches here are of course unfortunate
> and both more verification and documentation would be
> nice.  verify_gimple_switch only verifies all case labels
> have the same type, the type of the switch argument is
> not verified in any way against that type.

When looking at the verification, I have noticed a bug in it.

The verification that CASE_HIGH (if present) has the same type as CASE_LOW
is only performed for the case label 2 and higher, case label 1 (the first
one after the default label) isn't checked.

The following patch fixes that, it will uselessly also compare
TREE_TYPE (CASE_LOW (elt)) != elt_type for the case label 1, but I think
that isn't that expensive and helps readability of the code.

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

2020-08-31  Jakub Jelinek  <jakub@redhat.com>

	* tree-cfg.c (verify_gimple_switch): If the first non-default case
	label has CASE_HIGH, verify it has the same type as CASE_LOW.

--- gcc/tree-cfg.c.jj	2020-08-27 18:42:35.660711349 +0200
+++ gcc/tree-cfg.c	2020-08-27 22:46:34.574154370 +0200
@@ -4809,17 +4809,7 @@ verify_gimple_switch (gswitch *stmt)
 	  return true;
 	}
 
-      if (elt_type)
-	{
-	  if (TREE_TYPE (CASE_LOW (elt)) != elt_type
-	      || (CASE_HIGH (elt) && TREE_TYPE (CASE_HIGH (elt)) != elt_type))
-	    {
-	      error ("type mismatch for case label in switch statement");
-	      debug_generic_expr (elt);
-	      return true;
-	    }
-	}
-      else
+      if (! elt_type)
 	{
 	  elt_type = TREE_TYPE (CASE_LOW (elt));
 	  if (TYPE_PRECISION (index_type) < TYPE_PRECISION (elt_type))
@@ -4828,6 +4818,13 @@ verify_gimple_switch (gswitch *stmt)
 	      return true;
 	    }
 	}
+      if (TREE_TYPE (CASE_LOW (elt)) != elt_type
+          || (CASE_HIGH (elt) && TREE_TYPE (CASE_HIGH (elt)) != elt_type))
+	{
+	  error ("type mismatch for case label in switch statement");
+	  debug_generic_expr (elt);
+	  return true;
+	}
 
       if (prev_upper_bound)
 	{


	Jakub



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