Parser.y.pp needs special treatment with -fcmm-sink

This bug is really more of a reminder, but it's critical for the 7.8.1 release.

Right now, Parser.y.pp uses a very weird hack to pass -fcmm-sink to the compiler. Here's the relevant comment:

-- CPP tricks because we want the directives in the output of the
-- first CPP pass.
--
-- Clang note, 6/17/2013 by aseipp: It is *extremely* important (for
-- some reason) that there be a line of whitespace between the two
-- definitions here, and the subsequent use of __IF_GHC_77__ - this
-- seems to be a bug in clang or something, where having the line of
-- whitespace will make the preprocessor correctly format the rendered
-- lines in the 'two step' CPP pass. No, this is not a joke.
#define __IF_GHC_77__ #if __GLASGOW_HASKELL__ >= 707
#define __ENDIF__ #endif

__IF_GHC_77__
-- Required on x86 to avoid the register allocator running out of
-- stack slots when compiling this module with -fPIC -dynamic.
{-# OPTIONS_GHC -fcmm-sink #-}
__ENDIF__

This is because the parser is first preprocessed before being run with GHC (which again preprocesses,) so we want the resulting #ifdef in the final .hs file.

Things to note:

• We really shouldn't be doing this, it's amazingly fragile. I think the correct thing to do is to ensure the build system correctly passes -fcmm-sink during the stage[2,3] build.
• ./configure.ac needs to check to see if the bootstrapping compiler is ghc >= 7.7 (or 7.8) and if it is, also pass -fcmm-sink during the stage1 build.
• This hack needs to be removed once we can rely on >= 7.8 for bootstrap. Probably something like the hypothetical 7.12-7.14 timeframe.

Trac metadata

Trac field	Value
Version	7.7
Type	Bug
TypeOfFailure	OtherFailure
Priority	highest
Resolution	Unresolved
Component	Build System
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