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We used to add the options when the way was enabled, but this caused
problems with the static/dynamic choice, as once the 'dynamic' options
had been added it wasn't easy to remove them. We therefore didn't allow
-static on the commandline if we'd already seen -static, which kludged
around the issue.

But apart from being unsatisfactory in the first place, this is a
problem if we want to allow -dynamic being on by default, as there
wouldn't be any way to turn it off.

So now we add C/CPP/linker flags required by the 'way's when flags
are requested, rather than during flag parsing.

The current fix is relatively dumb as far as where to add HpLim
checks: it will always perform a check unless we know that we're
returning from a closure or we are doing a non let-no-escape case
analysis.  The performance impact on the nofib suite looks like this:

            Min          +5.7%     -0.0%     -6.5%     -6.4%    -50.0%
            Max          +6.3%     +5.8%     +5.0%     +5.5%     +0.8%
 Geometric Mean          +6.2%     +0.1%     +0.5%     +0.5%     -0.8%

Overall, the executable bloat is the biggest problem, so we keep the old
omit-yields optimization on by default. Remember that if you need an
interruptibility guarantee, you need to recompile all of your libraries
with -fno-omit-yields.

A better fix would involve only inserting the yields necessary to break
loops; this is left as future work.
Signed-off-by: Edward Z. Yang <ezyang@mit.edu>

This frees wORD_SIZE up to be moved out of HaskellConstants

We now also generate nice wrappers for the platformConstants
methods. For now it's all commented out as the definitions
conflict with those in Constants.

We now generate a platformConstants file that we can read at runtime.

It's now just 'dopt Opt_Ticky'

We used to use a list lookup that couldn't fail. Now we just use
functions.

There were 3 overlapping entries for WayPar; I've commented out the ones
that were shadowed for now.

To explicitly choose whether you want an unregisterised build you now
need to use the "--enable-unregisterised"/"--disable-unregisterised"
configure flags.

This is a bit odd by itself, but it's a stepping stone on the way to
putting "target unregisterised" into the settings file.

Related to #4862

They were getting baked into Config.hs before.

Instead of relying on common-block-elimination to share return
continuations in the common case (case-alternative heap checks) we do
it explicitly.  This isn't hard to do, is more robust, and saves some
compilation time.  Full commentary in Note [sharing continuations].

Proc-point splitting is only required by backends that do not support
having proc-points within a code block (that is, everything except the
native backend, i.e. LLVM and C).

Not doing proc-point splitting saves some compilation time, and might
produce slightly better code in some cases.

Keep the warning off for template-haskell and bytestring for the moment.

All the flags that 'ways' imply are now dynamic

Also, temporarely disable that warning for validate builds, until we
finish fixing them all.

I suspect I have done the wrong thing; I hope someone can improve.

The only difference between SevDump and SevOutput in defaultLogAction is
an extra blank line, so we don't need a separate hPrintDump function.

Also make -ddump-to-file consistent with the stdout version, by avoiding
to add the extra empty line when dumping rules.

Hopefully I've kept the logic the same, and we now generate warnings if
the user does -fno-PIC but we ignore them (e.g. because they're on OS X
amd64).

We now handle the preprocessor options the same way as the gcc options
(picCCOpts).