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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.
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