Re: patch to fix constant math - first small patch - patch ping for the next stage 1

[Richard Biener <richard dot guenther at gmail dot com>]

On Tue, Apr 2, 2013 at 9:08 PM, Kenneth Zadeck <zadeck@naturalbridge.com> wrote:
> this time for sure.

Almost ...

diff --git a/gcc/hwint.c b/gcc/hwint.c
index 330b42c..92d54a3 100644
--- a/gcc/hwint.c
+++ b/gcc/hwint.c
@@ -204,3 +204,35 @@ least_common_multiple (HOST_WIDE_INT a, HOST_WIDE_INT b)
 {
   return mul_hwi (abs_hwi (a) / gcd (a, b), abs_hwi (b));
 }
+
+#ifndef ENABLE_CHECKING

#ifdef ENABLE_CHECKING

+/* Sign extend SRC starting from PREC.  */
+
+HOST_WIDE_INT
+sext_hwi (HOST_WIDE_INT src, unsigned int prec)
+{
+  gcc_checking_assert (prec <= HOST_BITS_PER_WIDE_INT);
+

Ok with that change.  (maybe catch one random use of the pattern
in code and use the helpers - that would have catched this issue)

Thanks,
Richard.



> kenny
>
> On 04/02/2013 10:54 AM, Richard Biener wrote:
>>
>> On Tue, Apr 2, 2013 at 3:49 PM, Kenneth Zadeck <zadeck@naturalbridge.com>
>> wrote:
>>>
>>> Richard,
>>>
>>> did everything that you asked here.  bootstrapped and regtested on
>>> x86-64.
>>> ok to commit?
>>
>> diff --git a/gcc/hwint.c b/gcc/hwint.c
>> index 330b42c..7e5b85c 100644
>> --- a/gcc/hwint.c
>> +++ b/gcc/hwint.c
>> @@ -204,3 +204,33 @@ least_common_multiple (HOST_WIDE_INT a, HOST_WIDE_INT
>> b)
>>   {
>>     return mul_hwi (abs_hwi (a) / gcd (a, b), abs_hwi (b));
>>   }
>> +
>> +#ifndef ENABLE_CHECKING
>> +/* Sign extend SRC starting from PREC.  */
>> +
>> +HOST_WIDE_INT
>> +sext_hwi (HOST_WIDE_INT src, unsigned int prec)
>>
>> this should go to hwint.h, and without the masking of prec.
>> while ...
>>
>> diff --git a/gcc/hwint.h b/gcc/hwint.h
>> index da62fad..9dddf05 100644
>> --- a/gcc/hwint.h
>> +++ b/gcc/hwint.h
>> @@ -276,4 +316,42 @@ extern HOST_WIDE_INT pos_mul_hwi (HOST_WIDE_INT,
>> HOST_WIDE_INT);
>>   extern HOST_WIDE_INT mul_hwi (HOST_WIDE_INT, HOST_WIDE_INT);
>>   extern HOST_WIDE_INT least_common_multiple (HOST_WIDE_INT,
>> HOST_WIDE_INT);
>>
>> +/* Sign extend SRC starting from PREC.  */
>> +
>> +#ifdef ENABLE_CHECKING
>> +extern HOST_WIDE_INT sext_hwi (HOST_WIDE_INT, unsigned int);
>> +#else
>> +static inline HOST_WIDE_INT
>> +sext_hwi (HOST_WIDE_INT src, unsigned int prec)
>> +{
>> +  gcc_checking_assert (prec <= HOST_BITS_PER_WIDE_INT);
>>
>> this should go to hwint.c (also without masking prec).
>>
>> Richard.
>>
>>
>>
>>
>>> kenny
>>>
>>>
>>> On 04/02/2013 05:38 AM, Richard Biener wrote:
>>>>
>>>> On Sun, Mar 31, 2013 at 7:51 PM, Kenneth Zadeck
>>>> <zadeck@naturalbridge.com> wrote:
>>>>>
>>>>> richard,
>>>>>
>>>>> I was able to add everything except for the checking asserts.    While
>>>>> I
>>>>> think that this is a reasonable idea, it is difficult to add that to a
>>>>> function that is defined in hwint.h because of circular includes.   I
>>>>> could
>>>>> move this another file (though this appears to be the logical correct
>>>>> place
>>>>> for it), or we can do without the asserts.
>>>>>
>>>>> The context is that [sz]ext_hwi is that are used are over the compiler
>>>>> but
>>>>> are generally written out long.   The wide-int class uses them also,
>>>>> but
>>>>> wide-int did not see like the right place for them to live and i
>>>>> believe
>>>>> that you suggested that i move them.
>>>>>
>>>>> ok to commit, or do you have a suggested resolution to the assert
>>>>> issue?
>>>>
>>>> Yes, do
>>>>
>>>> #ifdef ENABLE_CHECKING
>>>> extern HOST_WIDE_INT sext_hwi (HOST_WIDE_INT, unsigned int);
>>>> #else
>>>> +/* Sign extend SRC starting from PREC.  */
>>>> +
>>>> +static inline HOST_WIDE_INT
>>>> +sext_hwi (HOST_WIDE_INT src, unsigned int prec)
>>>> +{
>>>> +  if (prec == HOST_BITS_PER_WIDE_INT)
>>>> +    return src;
>>>> +  else
>>>> +    {
>>>>           int shift = HOST_BITS_PER_WIDE_INT - prec;
>>>> +      return (src << shift) >> shift;
>>>> +    }
>>>> +}
>>>> #endif
>>>>
>>>> and for ENABLE_CHECKING only provide an out-of-line implementation
>>>> in hwint.c.  That's how we did it with abs_hwi (well, we just do not
>>>> provide
>>>> an inline variant there - that's another possibility).
>>>>
>>>> Note that hwint.h is always included after config.h so the
>>>> ENABLE_CHECKING
>>>> definition should be available.
>>>>
>>>> Richard.
>>>>
>>>>> kenny
>>>>>
>>>>>
>>>>> On 03/27/2013 10:13 AM, Richard Biener wrote:
>>>>>>
>>>>>> On Wed, Feb 27, 2013 at 1:22 AM, Kenneth Zadeck
>>>>>> <zadeck@naturalbridge.com> wrote:
>>>>>>>
>>>>>>> Here is the first of my wide int patches with joseph's comments and
>>>>>>> the
>>>>>>> patch rot removed.
>>>>>>>
>>>>>>> I would like to get these pre approved for the next stage 1.
>>>>>>
>>>>>> +      int shift = HOST_BITS_PER_WIDE_INT - (prec &
>>>>>> (HOST_BITS_PER_WIDE_INT - 1));
>>>>>>
>>>>>> I think this should gcc_checking_assert that prec is not out of range
>>>>>> (any reason why prec is signed int and not unsigned int?) rather than
>>>>>> ignore bits in prec.
>>>>>>
>>>>>> +static inline HOST_WIDE_INT
>>>>>> +zext_hwi (HOST_WIDE_INT src, int prec)
>>>>>> +{
>>>>>> +  if (prec == HOST_BITS_PER_WIDE_INT)
>>>>>> +    return src;
>>>>>> +  else
>>>>>> +    return src & (((HOST_WIDE_INT)1
>>>>>> +                  << (prec & (HOST_BITS_PER_WIDE_INT - 1))) - 1);
>>>>>> +}
>>>>>>
>>>>>> likewise.  Also I'm not sure I agree about the signedness of the
>>>>>> result
>>>>>> /
>>>>>> src.
>>>>>> zext_hwi (-1, HOST_BITS_PER_WIDE_INT) < 0 is true which is odd.
>>>>>>
>>>>>> The patch misses context of uses, so I'm not sure what the above
>>>>>> functions
>>>>>> are intended to do.
>>>>>>
>>>>>> Richard.
>>>>>>
>>>>>>> On 10/05/2012 08:14 PM, Joseph S. Myers wrote:
>>>>>>>>
>>>>>>>> On Fri, 5 Oct 2012, Kenneth Zadeck wrote:
>>>>>>>>
>>>>>>>>> +# define HOST_HALF_WIDE_INT_PRINT "h"
>>>>>>>>
>>>>>>>> This may cause problems on hosts not supporting %hd (MinGW?), and
>>>>>>>> there's
>>>>>>>> no real need for using "h" here given the promotion of short to int;
>>>>>>>> you
>>>>>>>> can just use "" (rather than e.g. needing special handling in
>>>>>>>> xm-mingw32.h
>>>>>>>> like is done for HOST_LONG_LONG_FORMAT).
>>>>>>>>
>