Produce new-style Cmm from the Cmm parser

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.

1 files changed, 3 insertions, 4 deletions

diff --git a/compiler/codeGen/StgCmmUtils.hs b/compiler/codeGen/StgCmmUtils.hs
index 386e7f46d6..138e00ee52 100644
--- a/compiler/codeGen/StgCmmUtils.hs
+++ b/compiler/codeGen/StgCmmUtils.hs
@@ -36,7 +36,6 @@ module StgCmmUtils (
         addToMem, addToMemE, addToMemLbl,
         mkWordCLit,
         newStringCLit, newByteStringCLit,
-        packHalfWordsCLit,
         blankWord
   ) where
 
@@ -196,9 +195,9 @@ emitRtsCallGen res pkg fun args safe
     call updfr_off =
       if safe then
         emit =<< mkCmmCall fun_expr res' args' updfr_off
-      else
-        emit $ mkUnsafeCall (ForeignTarget fun_expr
-                         (ForeignConvention CCallConv arg_hints res_hints)) res' args'
+      else do
+        let conv = ForeignConvention CCallConv arg_hints res_hints CmmMayReturn
+        emit $ mkUnsafeCall (ForeignTarget fun_expr conv) res' args'
     (args', arg_hints) = unzip args
     (res',  res_hints) = unzip res
     fun_expr = mkLblExpr (mkCmmCodeLabel pkg fun)