Re: [commit: ghc] master: Fix popcnt calls (2293238)

On 01/11/12 17:29, Ian Lynagh wrote:
> Repository : ssh://darcs.haskell.org//srv/darcs/ghc
>
> On branch  : master
>
> http://hackage.haskell.org/trac/ghc/changeset/229323898b0809047b19b79c181085430cce9850
>
>> ---------------------------------------------------------------
>
> commit 229323898b0809047b19b79c181085430cce9850
> Author: Ian Lynagh <[email protected]>
> Date:   Thu Nov 1 14:13:05 2012 +0000
>
>      Fix popcnt calls
>
>      We don't want to narrow the argument size before making the foreign
>      call: Word8 still gets passed as a Word-sized argument

I'm not sure this is right (I added the narrowing, FWIW).  The fact that 
Word8 gets promoted to Word is part of the C ABI, and we don't want to 
do that when popcnt is being implemented directly by the native codegen. 
  I know it is currently broken on some platforms, but I think the fix 
is to implement the proper type promotion in the compilation of C calls.

Cheers,
	Simon



>> ---------------------------------------------------------------
>
>   compiler/codeGen/StgCmmPrim.hs |   15 +++++----------
>   1 files changed, 5 insertions(+), 10 deletions(-)
>
> diff --git a/compiler/codeGen/StgCmmPrim.hs b/compiler/codeGen/StgCmmPrim.hs
> index 650a12e..fe2a021 100644
> --- a/compiler/codeGen/StgCmmPrim.hs
> +++ b/compiler/codeGen/StgCmmPrim.hs
> @@ -485,16 +485,11 @@ emitPrimOp _      [] SetByteArrayOp [ba,off,len,c] =
>       doSetByteArrayOp ba off len c
>
>   -- Population count
> -emitPrimOp dflags [res] PopCnt8Op [w] =
> -  emitPopCntCall res (CmmMachOp (mo_WordTo8 dflags) [w]) W8
> -emitPrimOp dflags [res] PopCnt16Op [w] =
> -  emitPopCntCall res (CmmMachOp (mo_WordTo16 dflags) [w]) W16
> -emitPrimOp dflags [res] PopCnt32Op [w] =
> -  emitPopCntCall res (CmmMachOp (mo_WordTo32 dflags) [w]) W32
> -emitPrimOp _      [res] PopCnt64Op [w] =
> -  emitPopCntCall res w W64 -- arg always has type W64, no need to narrow
> -emitPrimOp dflags [res] PopCntOp [w] =
> -  emitPopCntCall res w (wordWidth dflags)
> +emitPrimOp _      [res] PopCnt8Op  [w] = emitPopCntCall res w W8
> +emitPrimOp _      [res] PopCnt16Op [w] = emitPopCntCall res w W16
> +emitPrimOp _      [res] PopCnt32Op [w] = emitPopCntCall res w W32
> +emitPrimOp _      [res] PopCnt64Op [w] = emitPopCntCall res w W64
> +emitPrimOp dflags [res] PopCntOp   [w] = emitPopCntCall res w (wordWidth dflags)
>
>   -- The rest just translate straightforwardly
>   emitPrimOp dflags [res] op [arg]
>
>
>
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