pprCallishMachOp_for_C: MO_Prefetch_Data 0 not supported

Compiling on linux-powerpc64, the build fails on:

ghc-stage1: panic! (the 'impossible' happened)
  (GHC version 7.7.20131010 for powerpc64-unknown-linux):
        pprCallishMachOp_for_C: MO_Prefetch_Data 0 not supported!

Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug

From file compiler/cmm/PprC.hs :

        (MO_Prefetch_Data _ ) -> unsupported
        --- we could support prefetch via "__builtin_prefetch"
        --- Not adding it for now

Anyone have ideas on how to make this work?

Trac metadata

Trac field	Value
Version	7.7
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
Test case
Differential revisions
BlockedBy
Related
Blocking
CC
Operating system
Architecture

mentioned in issue #3827 (closed)

changed weight to 5

added Tbug Trac import labels

The function prototype for __builtin_prefetch is:

void __builtin_prefetch( const void *addr, int rw, int locality );

but the MO_Prefetch_Data constructor only has one element.

Funny, someone else (I assume!) was also building HEAD on linux-powerpc64 last night and ran into this same issue.

For now, you can try this (untested) patch to simply make prefetches a no-op in the C backend: http://lpaste.net/94144

Ideally, you would output a __builtin_prefetch call where rw is 0, locality is the argument of the MO_Prefetch_Data constructor, and addr comes from the args field of the CmmUnsafeForeignCall. That looks pretty easy to do, by adding another special case for fn_addr and sending MO_Prefetch_Data _ to __builtin_prefetch in pprCallishMachOp_for_C.

urk, this is absolutely my fault, I didn't realize the c backend is used anymore! (seriously, had no idea, thought it was just a bitrotting thing in tree....). Otherwise i'd have added that too. My sincerest apologies for that.

reid's noop patch and sketch for how to do prefetch right sound.

mentioned in commit 896cee02

closed

Replying to [ticket:8437#comment:76046 rwbarton]:

Ideally, you would output a __builtin_prefetch call where rw is 0, locality is the argument of the MO_Prefetch_Data constructor, and addr comes from the args field of the CmmUnsafeForeignCall. That looks pretty easy to do, by adding another special case for fn_addr and sending MO_Prefetch_Data _ to __builtin_prefetch in pprCallishMachOp_for_C.

Please open a new task ticket if that is still needed. Commit 896cee02 should have fixed the powerpc64 build, so I'm closing this ticket if you agree.

Trac metadata

Trac field	Value
TypeOfFailure	OtherFailure → BuildingGhcFailed
Resolution	Unresolved → ResolvedFixed
Component	Compiler → Build System

added ghc build failure label

The new Hadrian build system has been merged. Relabeling the tickets concerning the legacy make build system to prevent confusion.

Trac metadata

Trac field	Value
Component	Build System → Build System (make)

added Pnormal label