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This removes the OldCmm data type and the CmmCvt pass that converts
new Cmm to OldCmm.  The backends (NCGs, LLVM and C) have all been
converted to consume new Cmm.

The main difference between the two data types is that conditional
branches in new Cmm have both true/false successors, whereas in OldCmm
the false case was a fallthrough.  To generate slightly better code we
occasionally need to invert a conditional to ensure that the
branch-not-taken becomes a fallthrough; this was previously done in
CmmCvt, and it is now done in CmmContFlowOpt.

We could go further and use the Hoopl Block representation for native
code, which would mean that we could use Hoopl's postorderDfs and
analyses for native code, but for now I've left it as is, using the
old ListGraph representation for native code.

All Cmm procedures now include the set of global registers that are live on
procedure entry, i.e., the global registers used to pass arguments to the
procedure. Only global registers that are use to pass arguments are included in
this list.

(PicBaseReg + lit) + N  ==>  PicBaseReg + (lit+N)

The main change here is that the Cmm parser now allows high-level cmm
code with argument-passing and function calls.  For example:

foo ( gcptr a, bits32 b )
{
  if (b > 0) {
     // we can make tail calls passing arguments:
     jump stg_ap_0_fast(a);
  }

  return (x,y);
}

More details on the new cmm syntax are in Note [Syntax of .cmm files]
in CmmParse.y.

The old syntax is still more-or-less supported for those occasional
code fragments that really need to explicitly manipulate the stack.
However there are a couple of differences: it is now obligatory to
give a list of live GlobalRegs on every jump, e.g.

  jump %ENTRY_CODE(Sp(0)) [R1];

Again, more details in Note [Syntax of .cmm files].

I have rewritten most of the .cmm files in the RTS into the new
syntax, except for AutoApply.cmm which is generated by the genapply
program: this file could be generated in the new syntax instead and
would probably be better off for it, but I ran out of enthusiasm.

Some other changes in this batch:

 - The PrimOp calling convention is gone, primops now use the ordinary
   NativeNodeCall convention.  This means that primops and "foreign
   import prim" code must be written in high-level cmm, but they can
   now take more than 10 arguments.

 - CmmSink now does constant-folding (should fix #7219)

 - .cmm files now go through the cmmPipeline, and as a result we
   generate better code in many cases.  All the object files generated
   for the RTS .cmm files are now smaller.  Performance should be
   better too, but I haven't measured it yet.

 - RET_DYN frames are removed from the RTS, lots of code goes away

 - we now have some more canned GC points to cover unboxed-tuples with
   2-4 pointers, which will reduce code size a little.

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

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.

This reverts commit 5ff03ca7.

This reverts commit 3d8ab554.

No special-casing in any NCGs yet

 - inline x = R1, even if x occurs many times
 - inline past a store, if the expression is not a load
   (we could further refine this of course, but the idea here
   is to get reasonable code for not much effort)

We now carry around with CmmJump statements a list of
the STG registers that are live at that jump site.
This is used by the LLVM backend so it can avoid
unnesecarily passing around dead registers, improving
perfromance. This gives us the framework to finally
fix trac #4308.

This field was doing nothing.  I think it originally appeared in a
very old incarnation of the new code generator.

Simon Peyton Jones authored Aug 23, 2011 and Simon Marlow committed Aug 25, 2011

   CmmTop -> CmmDecl
   CmmPgm -> CmmGroup

I introduced this to support explicitly recording the info table label
in RawCmm for another patch I am working on, but it turned out to lead
to significant simplification in those parts of the compiler that
consume RawCmm.

Now, instead of lots of tests for null [CmmStatic] we have a simple
test of a Maybe, and have reduced the number of guys that need to know
how to convert entry->info labels by a TON. There are only 3 callers
of that function now!

Before this change the constant expression

   _ccI::I64 = (16 >> 7) + 1;

wouldn't be propagated, as it wouldn't be completely folded.  This
meant that this expression wouldn't be unrolled

    thawArray# arr# 0# 16# s#

The new code generator already does this correctly.

    * Rewrote cmmMachOpFold to cmmMachOpFoldM, which returns
      Nothing if no folding took place.
    * Wrote some generic mapping functions which take functions
      of form 'a -> Maybe a' and are smart about sharing.
    * Split up optimizations from PIC and PPC work in the native
      codegen, so they'll be easier to turn off later
      (they are not currently being turned off, however.)
    * Whitespace fixes!

ToDo: Turn off MachOp folding when new codegenerator is being used.
Signed-off-by: Edward Z. Yang <ezyang@mit.edu>

tibbe authored May 06, 2011 and Simon Marlow committed Jun 01, 2011

This exposes new constants that can be propagated.

tibbe authored May 06, 2011 and Simon Marlow committed Jun 01, 2011

Currently the mini-inliner would only forward substitute assignments
to registers that were used exactly once, to not risk duplicating
computation.  For constants there's no such risk so we always
substitute.  Prior to the change the Cmm

    fn
    {
        bits64 a, b;

        a = 1;
        b = a + a;
        RET_N(b);
    }

would be optimized as

    fn()    { []
            }
        ca: _cb::I64 = 1;
            R1 = _cb::I64 + _cb::I64;
            jump (I64[Sp + 0]) ();
    }

but after it would be optimized as

    fn()    { []
            }
        ca: R1 = 2;
            jump (I64[Sp + 0]) ();
    }

Note that this pass does not deal with the now dead assignment.

Signed-off-by: Edward Z. Yang <ezyang@mit.edu>

Signed-off-by: Edward Z. Yang <ezyang@mit.edu>

This change may constitute a substantial performance hit, due to the new
creation of a set for every instruction we emit.
Signed-off-by: Edward Z. Yang <ezyang@mit.edu>

This changes the new code generator to make use of the Hoopl package
for dataflow analysis.  Hoopl is a new boot package, and is maintained
in a separate upstream git repository (as usual, GHC has its own
lagging darcs mirror in http://darcs.haskell.org/packages/hoopl).

During this merge I squashed recent history into one patch.  I tried
to rebase, but the history had some internal conflicts of its own
which made rebase extremely confusing, so I gave up. The history I
squashed was:

  - Update new codegen to work with latest Hoopl
  - Add some notes on new code gen to cmm-notes
  - Enable Hoopl lag package.
  - Add SPJ note to cmm-notes
  - Improve GC calls on new code generator.

Work in this branch was done by:
   - Milan Straka <fox@ucw.cz>
   - John Dias <dias@cs.tufts.edu>
   - David Terei <davidterei@gmail.com>

Edward Z. Yang <ezyang@mit.edu> merged in further changes from GHC HEAD
and fixed a few bugs.