[GHC] #9407: Program produces different output when compiled with -O
#9407: Program produces different output when compiled with -O -------------------------------------+------------------------------------- Reporter: arotenberg | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.3 Keywords: | Operating System: Windows Architecture: x86_64 (amd64) | Type of failure: Incorrect Difficulty: Unknown | result at runtime Blocked By: | Test Case: Related Tickets: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- When compiled and run as {{{ ghc Subtlety.hs Subtlety }}} the attached program generates the correct output of {{{ Just (Vec3 0.0 0.0 1.0) }}} but when compiled and run using {{{ ghc -O Subtlety.hs Subtlety }}} the program's output is {{{ Just (Vec3 0.0 0.9805806756909202 0.19611613513818404) }}} Furthermore, subtle changes to the source code (like removing the strictness on the `Vec3` type's fields) can alter the behavior of the compiled program. I am using GHC 7.8.3 x86-64 from Haskell Platform 2014.2.0.0 RC2 on Windows 8. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9407 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#9407: Program produces different output when compiled with -O -------------------------------------+------------------------------------- Reporter: arotenberg | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.3 Resolution: | Keywords: Operating System: Windows | Architecture: x86_64 (amd64) Type of failure: Incorrect | Difficulty: Unknown result at runtime | Blocked By: Test Case: | Related Tickets: Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Comment (by rwbarton): How odd. I can't reproduce on GHC 7.8.3 x86-64 on Debian. Note that the output of the optimized program is `normalized (Vec3 0 5 1)`, so it looks like some of the x/y/z-coordinates are getting mixed up somehow. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9407#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#9407: Program produces different output when compiled with -O -------------------------------------+------------------------------------- Reporter: arotenberg | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.3 Resolution: | Keywords: Operating System: Windows | Architecture: x86_64 (amd64) Type of failure: Incorrect | Difficulty: Unknown result at runtime | Blocked By: Test Case: | Related Tickets: Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Comment (by simonpj): I can't reproduce the behaviour either, though I am not using precisely 7.8.3. Can other people reproduce? Can you compile both ways with `-dverbose-core2core -ddump-occur-anal -ddump-rule-rewrites -ddump-inlinings` and attach the results? Simon -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9407#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#9407: Program produces different output when compiled with -O -------------------------------------+------------------------------------- Reporter: arotenberg | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.3 Resolution: | Keywords: Operating System: Windows | Architecture: x86_64 (amd64) Type of failure: Incorrect | Difficulty: Unknown result at runtime | Blocked By: Test Case: | Related Tickets: Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Comment (by simonpj): Note to self: however with HEAD (but not with 7.8) I get {{{ WARNING: file compiler/simplCore/SimplCore.lhs, line 629 Simplifier bailing out after 4 iterations [584, 82, 104, 18] Size = {terms: 655, types: 264, coercions: 12} }}} so I'm getting more simplifier iterations apparently. Not related to the issue at hand, though. Simon -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9407#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#9407: Program produces different output when compiled with -O -------------------------------------+------------------------------------- Reporter: arotenberg | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.3 Resolution: | Keywords: Operating System: Windows | Architecture: x86_64 (amd64) Type of failure: Incorrect | Difficulty: Unknown result at runtime | Blocked By: Test Case: | Related Tickets: Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Comment (by arotenberg): I have verified that I can consistently recreate the issue on another computer running Windows 7 x86-64 with GHC 7.8.3. I believe the issue was also present in 7.8.2, since I upgraded to 7.8.3 with the express purpose of seeing if this issue had been fixed. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9407#comment:4 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#9407: Program produces different output when compiled with -O -------------------------------------+------------------------------------- Reporter: arotenberg | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.3 Resolution: | Keywords: Operating System: Windows | Architecture: x86_64 (amd64) Type of failure: Incorrect | Difficulty: Unknown result at runtime | Blocked By: Test Case: | Related Tickets: Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Comment (by arotenberg): I have now also verified that this problem does ''not'' occur on 32-bit Windows nor when using 32-bit GHC on 64-bit Windows. But you should be able to reproduce it if you use 64-bit Windows and 64-bit GHC 7.8.3. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9407#comment:5 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#9407: Program produces different output when compiled with -O -------------------------------------+------------------------------------- Reporter: arotenberg | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.3 Resolution: | Keywords: Operating System: Windows | Architecture: x86_64 (amd64) Type of failure: Incorrect | Difficulty: Unknown result at runtime | Blocked By: Test Case: | Related Tickets: Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Comment (by simonpj): OK so it seems likely to be something to do with 64-bit floating-point arithmetic. I wonder if it makes a difference whether you use the native code generator or LLVM? Does anyone feel able to investigate? The program isn't very big, and has no dependencies other than `Prelude`. Simon -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9407#comment:6 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#9407: Program produces different output when compiled with -O -------------------------------------+------------------------------------- Reporter: arotenberg | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.3 Resolution: | Keywords: Operating System: Windows | Architecture: x86_64 Type of failure: Incorrect result | (amd64) at runtime | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by rdragon): It looks like this issue has been fixed in GHC 7.10.2 or before. I can reproduce the problem with GHC 7.8.3, but not with 7.10.2. In both cases I use the 64-bit version. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9407#comment:7 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#9407: Program produces different output when compiled with -O
-------------------------------------+-------------------------------------
Reporter: arotenberg | Owner:
Type: bug | Status: new
Priority: normal | Milestone:
Component: Compiler | Version: 7.8.3
Resolution: | Keywords:
Operating System: Windows | Architecture: x86_64
Type of failure: Incorrect result | (amd64)
at runtime | Test Case:
Blocked By: | Blocking:
Related Tickets: | Differential Rev(s):
Wiki Page: |
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Comment (by Thomas Miedema
#9407: Program produces different output when compiled with -O -------------------------------------+------------------------------------- Reporter: arotenberg | Owner: Type: bug | Status: closed Priority: normal | Milestone: Component: Compiler | Version: 7.8.3 Resolution: fixed | Keywords: Operating System: Windows | Architecture: x86_64 | (amd64) Type of failure: Incorrect result | Test Case: at runtime | numeric/should_run/T9407 Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by thomie): * status: new => closed * testcase: => numeric/should_run/T9407 * resolution: => fixed Comment: Replying to [comment:7 rdragon]:
It looks like this issue has been fixed in GHC 7.10.2 or before. I can reproduce the problem with GHC 7.8.3, but not with 7.10.2. In both cases I use the 64-bit version.
Since bisecting pre-7.10 commit ranges is rather difficult, I say we leave it at this. Let's hope it's really fixed! If someone really wants to investigate further, they can of course do so, and reopen this ticket. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9407#comment:9 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#9407: Program produces different output when compiled with -O -------------------------------------+------------------------------------- Reporter: arotenberg | Owner: Type: bug | Status: closed Priority: normal | Milestone: Component: Compiler | Version: 7.8.3 Resolution: fixed | Keywords: Operating System: Windows | Architecture: x86_64 | (amd64) Type of failure: Incorrect result | Test Case: at runtime | numeric/should_run/T9407 Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by rwbarton): I wonder if this might have been the same bug as #10521. If so then it should be broken in 7.8 and 7.10.1 but not 7.6 or 7.10.2. I have no specific theory about why it would be Windows-only though. If someone would care to test 7.10.1 and 7.6 on Windows, I would be curious to know the results. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9407#comment:10 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#9407: Program produces different output when compiled with -O -------------------------------------+------------------------------------- Reporter: arotenberg | Owner: Type: bug | Status: closed Priority: normal | Milestone: Component: Compiler | Version: 7.8.3 Resolution: fixed | Keywords: Operating System: Windows | Architecture: x86_64 | (amd64) Type of failure: Incorrect result | Test Case: at runtime | numeric/should_run/T9407 Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by rdragon): Replying to [comment:10 rwbarton]:
If someone would care to test 7.10.1 and 7.6 on Windows, I would be curious to know the results.
I tested with GHC 7.6.3 and 7.10.1 on Windows 64bit. The issue was already present in 7.6.3 (I got the wrong output), but was already fixed in 7.10.1. Looks like a different bug, I'm afraid. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9407#comment:11 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
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