[Issue 9387] New: Compiler switch -O changes behavior of correct code

[d-bugmail at puremagic.com]

http://d.puremagic.com/issues/show_bug.cgi?id=9387

           Summary: Compiler switch -O changes behavior of correct code
           Product: D
           Version: D2
          Platform: x86_64
        OS/Version: Mac OS X
            Status: NEW
          Severity: major
          Priority: P2
         Component: DMD
        AssignedTo: nobody at puremagic.com
        ReportedBy: stephan.schiffels at mac.com


--- Comment #0 from Stephan <stephan.schiffels at mac.com> 2013-01-24 07:56:09 PST ---
Created an attachment (id=1182)
Source file with program that

The attached program implements a part of Brent's minimization algorithm for
one-dimensionsal functions. The code is from Numerical Recipes 3rd edition.

I use dmd 2.061/

When I run the program with "rdmd brent_test.d" it runs fine and gives the
correct result.

When I run it with optimization, i.e. with "rdmd -O brent_test.d", it behaves
differently. It enters some infinite loop and eventually throws the expected
exception for too many iterations.

You can see that I placed a writefln() into line 45, which outputs the value of
variable a. When you move this writefln statement just one line below, i.e.
below the if-statement, the code runs fine, even with optimization.

I colleague of mine suggested that there might be a bug related to a large
number of local variables. Maybe some limiting number of registers causes the
machine to cache things into memory and pulling them back in a wrong way or
something.

Appreciate help!

Stephan

-- 
Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email
------- You are receiving this mail because: -------