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Re: [RFA][PATCH] Improve VRP of COND_EXPR_CONDs


On 04/08/2013 03:45 AM, Richard Biener wrote:

@@ -8584,6 +8584,43 @@ simplify_cond_using_ranges (gimple stmt)
         }
      }

+  /* If we have a comparison of a SSA_NAME boolean against
+     a constant (which obviously must be [0..1]).  See if the
+     SSA_NAME was set by a type conversion where the source
+     of the conversion is another SSA_NAME with a range [0..1].
+
+     If so, we can replace the SSA_NAME in the comparison with
+     the RHS of the conversion.  This will often make the type
+     conversion dead code which DCE will clean up.  */
+  if (TREE_CODE (op0) == SSA_NAME
+      && TREE_CODE (TREE_TYPE (op0)) == BOOLEAN_TYPE

Use

        (TREE_CODE (TREE_TYPE (op0)) == BOOLEAN_TYPE
         || (INTEGRAL_TYPE_P (TREE_TYPE (op0))
             && TYPE_PRECISION (TREE_TYPE (op0)) == 1))

to catch some more cases.
Good catch.  Done.


+      && is_gimple_min_invariant (op1))

In this case it's simpler to test TREE_CODE (op1) == INTEGER_CST.
Agreed & fixed.


+    {
+      gimple def_stmt = SSA_NAME_DEF_STMT (op0);
+      tree innerop;
+
+      if (!is_gimple_assign (def_stmt)
+         || !CONVERT_EXPR_CODE_P (gimple_assign_rhs_code (def_stmt)))
+       return false;
+
+      innerop = gimple_assign_rhs1 (def_stmt);
+
+      if (!SSA_NAME_OCCURS_IN_ABNORMAL_PHI (innerop))

As Steven said, the abnormal check is not necessary, but for completeness
you should check TREE_CODE (innerop) == SSA_NAME.  Valid (but
unfolded) GIMPLE can have (_Bool) 1, too.
Agreed & fixed.


Note that we already have code with similar functionality (see if a
conversion would alter the value of X) as part of optimizing
(T1)(T2)X to (T1)X in simplify_conversion_using_ranges.  Maybe
a part of it can be split out and used to simplify conditions for
a bigger range of types than just compares against boolean 0/1.
That may be a follow-up -- there's still several of these things I'm looking at. I wanted to go ahead and start pushing out those which were clearly improvements rather than queue them while I looked at all the oddities I'm seeing in the dumps.

jeff


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