On 12/06/2014 16:12, Edward Ned Harvey (mono) wrote:
From: [email protected] [mailto:mono-list-
[email protected]] On Behalf Of David Burnett
I may have found a compiler bug, but as I'm fairly new to c# I thought I'd
First things first, how can we recreate the bug? I tried some rudimentary
testing based on the code you posted, and I failed to get the described result.
In all the cases I tried, I got x += x behaving as you would expect it to
behave. The same as x *= 2 (for ints between 1 and 2047).
What version of mono are you using?
Macintosh:Release vargol$ mono --version
Mono JIT compiler version 3.2.7 ((no/40f92d5 Thu Feb 6 18:29:16 EST 2014)
Copyright (C) 2002-2014 Novell, Inc, Xamarin Inc and Contributors.
www.mono-project.com
TLS: normal
SIGSEGV: altstack
Notification: kqueue
Architecture: x86
Disabled: none
Misc: softdebug
LLVM: yes(3.4svn-mono-(no/e656cac)
GC: sgen
running on OSX 10.6.8, 32 bit edition.
On advice of Eric [email protected] I've run monodis on the fixed and 'broken'
versions of the Assembly and the il created looks valid the diff is below.
I'm by no means an expert I'm assuming ldloc.0 twice followed by add
is loading median into two registers and adding.
*** 33324,33331 ****
IL_0022: bgt IL_0036
IL_0027: ldloc.0
! IL_0028: ldc.i4.2
! IL_0029: mul
IL_002a: stloc.0
IL_002b: ldloc.0
IL_002c: ldarg.3
--- 33324,33331 ----
IL_0022: bgt IL_0036
IL_0027: ldloc.0
! IL_0028: ldloc.0
! IL_0029: add
IL_002a: stloc.0
IL_002b: ldloc.0
IL_002c: ldarg.3
So its not a compiler bug, but maybe run time or JIT compiler bug.
I've tried running the bad version using --llvm and it seems to work correctly.
A fresh compile against .net also works correctly.
I've created a branch on my github repository holding the broken code and an
example file.
The repository is
https://github.com/Vargol/PhotonPump.git
The branch is mono_bug
to run the example
cd to the PhotonPump/SunflowSharp.Test/bin/Release directory and run
mono SunflowSharp.Test.exe ../../../examples/particle_chau.sc
It should eventually fail
...
LIGHT info: Balancing caustics photon map ...
index 1, start 1, end 3
4 median 1
3 median 1
index 3, start 2, end 3
4 median 1
System.IndexOutOfRangeException: Array index is out of range.
...
followed by a stack crawl
A successful run looks like
...
LIGHT info: Balancing caustics photon map ...
index 1, start 1, end 3
4 median 1
3 median 2
LIGHT info: Caustic photon map:
...
followed by much more
I guess however that this is off to mono-devel-list and a proper bug report.
and I've got a better test case to build.
Dave
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