Re: Patch to extend the fix PR53676 to unsigned char

[Richard Biener]

On Mon, Apr 22, 2013 at 5:21 PM, Laurent Alfonsi  wrote:
> The patch well fix the adobe_cpp performance regression on the int8_t type.
> But the same degradation exists on uint8_t type, which is not fixed by the
> patch referenced in PR53676.
>
> With the signed version, the code:
>result_5 = (signed char) ((int) result_2 + 2)
> is now well narrowed to:
>result_5 = (signed char) ((unsigned char) result_2 + 2)
>
> But with the unsigned version:
>result_5 = (unsigned char) ((int) result_2 + 2)
> is not narrowed to:
>result_5 = (unsigned char) ((unsigned char) result_2 + 2)
>
> As a consequence, result_5 is not detected as polynomial, and the loop is
> not removed.
> Tested on SH target. bootstrap + regression tests on
> x86_64-unknown-linux-gnu in progress.

Ok if testing succeeds, but please also adjust the comment before
the 2nd hunk and add a testcase that fails before and succeeds after.

Thanks,
Richard.

> Regards,
> Laurent
>

Patch to extend the fix PR53676 to unsigned char

[Laurent Alfonsi]

The patch well fix the adobe_cpp performance regression on the int8_t 
type. But the same degradation exists on uint8_t type, which is not 
fixed by the patch referenced in PR53676.


With the signed version, the code:
   result_5 = (signed char) ((int) result_2 + 2)
is now well narrowed to:
   result_5 = (signed char) ((unsigned char) result_2 + 2)

But with the unsigned version:
   result_5 = (unsigned char) ((int) result_2 + 2)
is not narrowed to:
   result_5 = (unsigned char) ((unsigned char) result_2 + 2)

As a consequence, result_5 is not detected as polynomial, and the loop 
is not removed.
Tested on SH target. bootstrap + regression tests on 
x86_64-unknown-linux-gnu in progress.


Regards,
Laurent

--- gcc.orig/gcc/tree-chrec.c	2013-04-22 13:20:03.0 +0200
+++ gcc/gcc/tree-chrec.c	2013-04-22 13:22:51.0 +0200
@@ -1346,13 +1346,12 @@
 res = fold_build2 (TREE_CODE (chrec), type,
 		   fold_convert (type, TREE_OPERAND (chrec, 0)),
 		   fold_convert (type, TREE_OPERAND (chrec, 1)));
-  /* Similar perform the trick that (signed char)((int)x + 2) can be
- narrowed to (signed char)((unsigned char)x + 2).  */
+  /* Similar perform the trick that ([un]signed char)((int)x + 2) can be
+ narrowed to ([un]signed char)((unsigned char)x + 2).  */
   else if (use_overflow_semantics
 	   && TREE_CODE (chrec) == POLYNOMIAL_CHREC
 	   && TREE_CODE (ct) == INTEGER_TYPE
 	   && TREE_CODE (type) == INTEGER_TYPE
-	   && TYPE_OVERFLOW_UNDEFINED (type)
 	   && TYPE_PRECISION (type) < TYPE_PRECISION (ct))
 {
   tree utype = unsigned_type_for (type);
--- gcc.orig/gcc/tree-scalar-evolution.c	2013-04-22 13:20:12.0 +0200
+++ gcc/gcc/tree-scalar-evolution.c	2013-04-22 13:21:43.0 +0200
@@ -1767,7 +1767,6 @@
   if (TREE_CODE (type) == INTEGER_TYPE
 	  && TREE_CODE (TREE_TYPE (rhs1)) == INTEGER_TYPE
 	  && TYPE_PRECISION (type) < TYPE_PRECISION (TREE_TYPE (rhs1))
-	  && TYPE_OVERFLOW_UNDEFINED (type)
 	  && TREE_CODE (rhs1) == SSA_NAME
 	  && (def = SSA_NAME_DEF_STMT (rhs1))
 	  && is_gimple_assign (def)