O2: allocateRegsAndSpill: Cannot read from uninitialized register %vI_s154O (GHC version 7.8.2 for x86_64-unknown-linux)

When building all world with -O2 I've stuck on wxhaskell (all versions):

[11 of 16] Compiling Graphics.UI.WX.Controls ( src/Graphics/UI/WX/Controls.hs, dist/build/Graphics/UI/WX/Controls.o )

<no location info>:
    ghc: panic! (the 'impossible' happened)
  (GHC version 7.8.2 for x86_64-unknown-linux):
        allocateRegsAndSpill: Cannot read from uninitialized register
    %vI_s154O

I've stripped it down to minimal complete example (but it significantly changed error message)

ghc: panic! (the 'impossible' happened)
  (GHC version 7.8.2 for x86_64-unknown-linux):
        RegAlloc.Liveness.computeLivenss
    SCCs aren't in reverse dependent order
    bad blockId c1tU
    [NONREC
        c1uc:
                movq $-8,%rbx
                andq $main:M.AlignLeft{v rb}_closure+1,%rbx
                addq $8,%rbp
                jmp *(%rbx),
     NONREC
...

Trac metadata

Trac field	Value
Version	7.8.2
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
Test case
Differential revisions
BlockedBy
Related
Blocking
CC
Operating system
Architecture	Unknown/Multiple

changed weight to 5

added Tbug Trac import labels

Attached file M.hs ($988).

test case

changed title from allocateRegsAndSpill: Cannot read from uninitialized register %vI_s154O (GHC version 7.8.2 for x86_64-unknown-linux) to O2: allocateRegsAndSpill: Cannot read from uninitialized register %vI_s154O (GHC version 7.8.2 for x86_64-unknown-linux)

Compile as:

ghc -c --make -hide-all-packages -package base -O2 M

-HEAD has the same disease:

[sf] ~/dev/git/ghc:inplace/bin/ghc-stage2 --make -O2 /tmp/M.hs 
[1 of 1] Compiling M                ( /tmp/M.hs, /tmp/M.o )
ghc-stage2: panic! (the 'impossible' happened)
  (GHC version 7.9.20140531 for x86_64-unknown-linux):
        RegAlloc.Liveness.computeLivenss
    SCCs aren't in reverse dependent order
    bad blockId c1cG
...

Trac metadata

Trac field	Value
TypeOfFailure	OtherFailure → CompileTimeCrash
Component	Compiler → Compiler (NCG)
Architecture	Unknown/Multiple → x86_64 (amd64)

The issue disappears when I revert commit f5879acd

changed milestone to %7.8.3

changed weight to 10

assigned to @simonmar

Investigating.

Trac metadata

Trac field	Value
Priority	normal → highest

I have a fix for this, indeed f5879acd was buggy. I'll do some more testing and measurement before I push. This is a blocker for 7.8.3.

Just to let you know I'm still working on this, hope to have it done today or tomorrow.

mentioned in commit e577a523

added 1 deleted label

closed

Merged.

Trac metadata

Trac field	Value
Resolution	Unresolved → ResolvedFixed

removed 1 deleted label

mentioned in issue #9303 (closed)