[project @ 2005-03-18 13:53:34 by simonmar]

Undo rev. 1.6, these changes shouldn't have been in this tree

diff --git a/ghc/compiler/nativeGen/RegisterAlloc.hs b/ghc/compiler/nativeGen/RegisterAlloc.hs
index 7c5a4bd..4f71fe1 100644 (file)
--- a/ghc/compiler/nativeGen/RegisterAlloc.hs
+++ b/ghc/compiler/nativeGen/RegisterAlloc.hs
@@ -80,58 +80,6 @@ The algorithm is roughly:
 
 -}
 
-{-
-Possible plan for x86 floating pt register alloc:
-
-  - The standard reg alloc procedure allocates pretend floating point
-    registers to the GXXX instructions.  We need to convert these GXXX
-    instructions to proper x86 FXXX instructions, using the FP stack for
-    registers.
-
-    We could do this in a separate pass, but it helps to have the
-    information about which real registers are live after the
-    instruction, so we do it at reg alloc time where that information
-    is already available.
-
-  - keep a mapping from %fakeN to FP stack slot in the monad.
-
-  - after assigning registers to the GXXX instruction, convert the
-    instruction to an FXXX instruction.  eg. 
-       - for GMOV just update the mapping, and ffree any dead regs.
-       - GLD:  just fld and update mapping
-         GLDZ: just fldz and update mapping
-         GLD1: just fld1 and update mapping
-       - GST: just fst and update mapping, ffree dead regs.
-          - special case for GST reg, where reg is st(0), we can fstp.
-       - for GADD fp1, fp2, fp3:
-         - easy way: fld fp2
-                     fld fp1
-                     faddp
-                     -- record that fp3 is now in %st(0), and all other
-                     -- slots are pushed down one.
-                     ffree fp1 -- if fp1 is dead now
-                     ffree fp2 -- if fp2 is dead now
-         - optimisation #1
-           - if fp1 is in %st(0) and is dead afterward
-               fadd %st(0), fp2
-               -- record fp3 is in %st(0)
-               ffree fp2 -- if fp2 is dead now
-           - if fp2 is in %st(0) and is dead afterward
-               fadd %st(0), fp1
-               -- record fp3 is in %st(0)
-           - if fp1 is in %st(0), fp2 is dead afterward
-               fadd fp2, %st(0)
-               -- record fp3 is in fp2's locn
-           - if fp2 is in %st(0), fp1 is dead afterward
-               fadd fp1, %st(0)
-               -- record fp3 is in fp1's locn
-
-  - we should be able to avoid the nasty ffree problems of the current
-    scheme.  The stack should be empty before doing a non-local
-    jump/call - we can assert that this is the case.
--}
-
-
 module RegisterAlloc (
        regAlloc
   ) where