[GHC] #10010: LLVM/optimized code for sqrt incorrect for negative values
#10010: LLVM/optimized code for sqrt incorrect for negative values -------------------------------------+------------------------------------- Reporter: glguy | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.4 (LLVM) | Operating System: Unknown/Multiple Keywords: | Type of failure: Incorrect result Architecture: | at runtime Unknown/Multiple | Blocked By: Test Case: | Related Tickets: Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- The LLVM sqrt intrinsic is undefined below values of -0.0 See http://llvm.org/docs/LangRef.html#llvm-sqrt-intrinsic In some versions of LLVM it returns 0.0 in this case, but in newer versions the return value is undefined. This causes the result of Haskell's sqrt to vary at negative values based on the codegen and optimization flags chosen. {{{ main = print (sqrt (-7 :: Double)) }}} {{{ $ ghc -O -fllvm Sqrt.hs [1 of 1] Compiling Main ( Sqrt.hs, Sqrt.o ) Linking Sqrt ... $ ./Sqrt 0.0 $ ghc -O Sqrt.hs [1 of 1] Compiling Main ( Sqrt.hs, Sqrt.o ) Linking Sqrt ... $ ./Sqrt NaN }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10010 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#10010: LLVM/optimized code for sqrt incorrect for negative values -------------------------------------+------------------------------------- Reporter: glguy | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler (LLVM) | Version: 7.8.4 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Incorrect result | Unknown/Multiple at runtime | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by tjakway): This works for me on HEAD (f21eedbc223c33b71ba323a44c25fcd512f61b52) All of the below were tried with -O0, -O1, and -O2 ghc 8.0.1 (doesn't support LLVM 3.8) and llvm 3.7 gives NaN HEAD with 3.7 also gives NaN HEAD with 3.8 gives NaN So at least it's OK going forward. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10010#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#10010: LLVM/optimized code for sqrt incorrect for negative values -------------------------------------+------------------------------------- Reporter: glguy | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler (LLVM) | Version: 7.8.4 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Incorrect result | Unknown/Multiple at runtime | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by tjakway): * cc: tjakway (added) -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10010#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#10010: LLVM/optimized code for sqrt incorrect for negative values -------------------------------------+------------------------------------- Reporter: glguy | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler (LLVM) | Version: 7.8.4 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Incorrect result | Unknown/Multiple at runtime | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by mpickering): @tjakway, does that mean this is fixed now? -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10010#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#10010: LLVM/optimized code for sqrt incorrect for negative values -------------------------------------+------------------------------------- Reporter: glguy | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler (LLVM) | Version: 7.8.4 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Incorrect result | Unknown/Multiple at runtime | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by tjakway): Replying to [comment:3 mpickering]:
@tjakway, does that mean this is fixed now? I don't remember why I didn't test it with LLVM 3.6 (probably just forgot) but we should probably do that before closing the ticket. I don't have any reason to think 3.6 would be different but just to be sure. Unless we don't support 3.6 with the latest version of GHC, then we can just close it now.
-- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10010#comment:4 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#10010: LLVM/optimized code for sqrt incorrect for negative values -------------------------------------+------------------------------------- Reporter: glguy | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler (LLVM) | Version: 7.8.4 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Incorrect result | Unknown/Multiple at runtime | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by George): This appears to be fixed in ghc 8.4.1 and llvm 6.0. The supported llvm for 8.4.1 is 5.0 but I have 6.0 as I'm on a Mac and did a brew update which overwrote 5.0 and installed 6.0. Can somebody verify with llvm 5.0? The following shows it works as described above: {{{ bash-3.2$ ghc --version The Glorious Glasgow Haskell Compilation System, version 8.4.1 bash-3.2$ opt -version LLVM (http://llvm.org/): LLVM version 6.0.0 Optimized build. Default target: x86_64-apple-darwin17.4.0 Host CPU: nehalem bash-3.2$ llc -version LLVM (http://llvm.org/): LLVM version 6.0.0 Optimized build. Default target: x86_64-apple-darwin17.4.0 Host CPU: nehalem ... ghc -O -fllvm Sqrt.hs [1 of 1] Compiling Main ( Sqrt.hs, Sqrt.o ) You are using an unsupported version of LLVM! Currently only 5.0 is supported. We will try though... Linking Sqrt ... bash-3.2$ ./Sqrt NaN bash-3.2$ }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10010#comment:5 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#10010: LLVM/optimized code for sqrt incorrect for negative values -------------------------------------+------------------------------------- Reporter: glguy | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler (LLVM) | Version: 7.8.4 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Incorrect result | Unknown/Multiple at runtime | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by George): * cc: George (added) -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10010#comment:6 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#10010: LLVM/optimized code for sqrt incorrect for negative values -------------------------------------+------------------------------------- Reporter: glguy | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.2.1 Component: Compiler (LLVM) | Version: 7.8.4 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: Incorrect result | Test Case: at runtime | libraries/base/tests/Numeric/sqrt Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by bgamari): * testcase: => libraries/base/tests/Numeric/sqrt * milestone: => 8.2.1 Comment: I'm rather surprised that wasn't caught by any existing testcase. Added a test in Phab:D4543. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10010#comment:7 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#10010: LLVM/optimized code for sqrt incorrect for negative values
-------------------------------------+-------------------------------------
Reporter: glguy | Owner: (none)
Type: bug | Status: new
Priority: normal | Milestone: 8.2.1
Component: Compiler (LLVM) | Version: 7.8.4
Resolution: | Keywords:
Operating System: Unknown/Multiple | Architecture:
| Unknown/Multiple
Type of failure: Incorrect result | Test Case:
at runtime | libraries/base/tests/Numeric/sqrt
Blocked By: | Blocking:
Related Tickets: | Differential Rev(s):
Wiki Page: |
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Comment (by Ben Gamari
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