Host/Target confusion in Dwarf output

Dave Korn dave.korn@artimi.com
Thu Jul 12 16:38:00 GMT 2007


On 12 July 2007 17:23, Michael Eager wrote:

> I was looking through dwarf2out.c, tracking down the
> cause for different assembly code being generated
> when gcc was run on 32-bit and 64-bit hosts.
> 
> In dwarf2out.c, there are several places where decisions
> about what to generate in the .s file are based on
> HOST_BITS_PER_WIDE_INT or HOST_BITS_PER_WIDE_LONG or
> similar.  For example, when generating a long long value,
> on a 32-bit host, the *target* assembly code will contain
> two .4byte ops, while on a 64-bit host, a single .8byte
> op is generated.  There are a number of other differences.
> 
> The assembler for a 32-bit target might not have a .8byte
> operator.  So, when run on a 32-bit host, everything is OK.
> On a 64-bit host, the assembly fails.
> 
> It seems to me that the same assembly code should be generated
> independent of whether gcc is run on a 32-bit or 64-bit
> host and all of these HOST_* tests should actually be
> target domain parameters, like BITS_PER_WORD.
> 
> Comments?


  Sounds right to me.  Basing codegen decisions on HOST_xxxx is just plain wrong and has been an ongoing source of bugs down the years.


    cheers,
      DaveK
-- 
Can't think of a witty .sigline today....



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