[wwwdocs] changes.html - Fortran changes

[wwwdocs] changes.html - Fortran changes

[Martin Liška]

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Hello.

Following patch documents DO loop changes which were done for upcoming GCC 7.1.

Thanks for feedback,
Martin

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Index: htdocs/gcc-7/changes.html
===================================================================
RCS file: /cvs/gcc/wwwdocs/htdocs/gcc-7/changes.html,v
retrieving revision 1.40
diff --unified -r1.40 changes.html
--- htdocs/gcc-7/changes.html	25 Jan 2017 10:10:56 -0000	1.40
+++ htdocs/gcc-7/changes.html	25 Jan 2017 13:09:28 -0000
@@ -362,6 +362,27 @@
     derived-type variables.
   </li>
 
+  <li>
+    DO loops with step equal to 1 or -1 generate faster code as they do not
+    have a loop preheader.  New warning <code>-Wundefined-do-loop</code>
+    warns when a loop iterates either to <code>HUGE(i)</code> (with step equal
+    to 1), or to <code>-HUGE(i)</code> (with step equal to -1). Apart from
+    that the invalid behaviour can be caught during run-time of a program with
+    <code>-fcheck=do</code>:
+    <blockquote><pre>
+program test
+  implicit none
+  integer(1) :: i
+  do i = -HUGE(i)+10, -HUGE(i)-1, -1
+    print *, i
+  end do
+end program test
+
+At line 8 of file /home/marxin/Programming/gcc/gcc/testsuite/gfortran.dg/do_check_12.f90
+Fortran runtime error: Loop iterates infinitely
+    </pre></blockquote>
+  </li>
+
 </ul>
 
 <!-- <h3 id="go">Go</h3> -->

Re: [wwwdocs] changes.html - Fortran changes

[Gerald Pfeifer]

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Hi Martin,

On Wed, 25 Jan 2017, Martin Liška wrote:
> Following patch documents DO loop changes which were done for upcoming 
> GCC 7.1.

thanks for putting this together.

Index: htdocs/gcc-7/changes.html
===================================================================
+  <li>
+    DO loops with step equal to 1 or -1 generate faster code as they do not
+    have a loop preheader.  New warning <code>-Wundefined-do-loop</code>
+    warns when a loop iterates either to <code>HUGE(i)</code> (with step equal
+    to 1), or to <code>-HUGE(i)</code> (with step equal to -1). Apart from
+    that the invalid behaviour can be caught during run-time of a program with
+    <code>-fcheck=do</code>:

Can you makr up DO as <code>DO</code> since it is a keyword?

"A new warning..."

"behavior" (since we use American English, or it also would be
programme ;-).

"run time" (according to https://gcc.gnu.org/codingconventions.html )

+At line 8 of file /home/marxin/Programming/gcc/gcc/testsuite/gfortran.dg/do_check_12.f90
+Fortran runtime error: Loop iterates infinitely
+    </pre></blockquote>

Here, can you shorten the filename to 
".../gcc/testsuite/gfortran.dg/do_check_12.f90" ?


This is fine with the changes above.

Thanks,
Gerald

Re: [wwwdocs] changes.html - Fortran changes

[Martin Liška]

On 01/26/2017 06:12 PM, Gerald Pfeifer wrote:
> Hi Martin,
> 
> On Wed, 25 Jan 2017, Martin Liška wrote:
>> Following patch documents DO loop changes which were done for upcoming 
>> GCC 7.1.
> 
> thanks for putting this together.
> 
> Index: htdocs/gcc-7/changes.html
> ===================================================================
> +  <li>
> +    DO loops with step equal to 1 or -1 generate faster code as they do not
> +    have a loop preheader.  New warning <code>-Wundefined-do-loop</code>
> +    warns when a loop iterates either to <code>HUGE(i)</code> (with step equal
> +    to 1), or to <code>-HUGE(i)</code> (with step equal to -1). Apart from
> +    that the invalid behaviour can be caught during run-time of a program with
> +    <code>-fcheck=do</code>:
> 
> Can you makr up DO as <code>DO</code> since it is a keyword?
> 
> "A new warning..."
> 
> "behavior" (since we use American English, or it also would be
> programme ;-).
> 
> "run time" (according to https://gcc.gnu.org/codingconventions.html )
> 
> +At line 8 of file /home/marxin/Programming/gcc/gcc/testsuite/gfortran.dg/do_check_12.f90
> +Fortran runtime error: Loop iterates infinitely
> +    </pre></blockquote>
> 
> Here, can you shorten the filename to 
> ".../gcc/testsuite/gfortran.dg/do_check_12.f90" ?
> 
> 
> This is fine with the changes above.
> 
> Thanks,
> Gerald
> 

Hi Gerald.

Thanks for review, all notes are fixed.

Martin