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(*
* This module manages the spill/reload process.
* The reason this is detached from the main module is that
* I can't understand the old code.
*
* Okay, now I understand the code.
*
* The new code does things slightly differently.
* Here, we are given an instruction and a list of registers to spill
* and reload. We rewrite the instruction until all instances of these
* registers are rewritten.
*
* (12/13/99) Some major caveats when spill coalescing/coloring is used:
* When parallel copies are generated and spill coalescing/coloring is used,
* two special cases have to be identified:
*
* Case 1 (spillLoc dst = spillLoc src)
* Suppose we have a parallel copy
* (u,v) <- (x,y)
* where u has to be spilled and y has to reloaded. When both
* u and y are mapped to location M. The following wrong code may
* be generated:
* M <- x (spill u)
* v <- M (reload y)
* This is incorrect. Instead, we generate a dummy copy and
* delay the spill after the reload, like this:
*
* tmp <- x (save value of u)
* v <- M (reload y)
* M <- tmp (spill u)
* Case 2 (spillLoc copyTmp = spillLoc src)
* Another case that can cause problems is when the spill location of
* the copy temporary is the same as that of one of the sources:
*
* (a, b, v) <- (b, a, u) where spillLoc(u) = spillLoc(tmp) = v
*
* The incorrect code is
* (a, b) <- (b, a)
* v <- M
* But then the shuffle code for the copy can clobber the location M.
*
* tmp <- M
* (a, b) <- (b, a)
* v <- tmp
*
* (Note that spillLoc copyTmp = spillLoc src can never happen)
*
* -- Allen
*)
functor RASpill
(structure InsnProps : INSN_PROPERTIES
structure Asm : INSTRUCTION_EMITTER (* where I = InsnProps.I *)
where type I.addressing_mode = InsnProps.I.addressing_mode
and type I.ea = InsnProps.I.ea
and type I.instr = InsnProps.I.instr
and type I.instruction = InsnProps.I.instruction
and type I.operand = InsnProps.I.operand
) : RA_SPILL =
struct
val debug = false
structure I = InsnProps.I
structure P = InsnProps
structure C = I.C
structure Core = RACore
structure G = Core.G
structure CB = CellsBasis
fun error msg = MLRiscErrorMsg.error("RASpill",msg)
val keep_dead_copies =
MLRiscControl.mkFlag
("ra-preserve-dead-copies",
"Dead copies are not removed when spilling")
fun dec1 n = Word.toIntX(Word.fromInt n - 0w1)
fun dec{block,insn} = {block=block,insn=dec1 insn}
structure T = RASpillTypes(I)
open T
fun uniq s = CB.SortedCells.return(CB.SortedCells.uniq s)
val i2s = Int.toString
fun pt2s{block,insn} = "b"^i2s block^":"^i2s insn
val Asm.S.STREAM{emit, ...} = Asm.makeStream[]
(* val spilledCopyTmps = MLRiscControl.getCounter "ra-spilled-copy-temps" *)
(*
* The following function performs spilling.
*)
fun spillRewrite
{graph=G as G.GRAPH{showReg, spilledRegs, nodes, mode, ...},
spill : spill,
spillCopyTmp : spillCopyTmp,
spillSrc : spillSrc,
renameSrc : renameSrc,
reload : reload,
reloadDst : reloadDst,
copyInstr : copyInstr,
cellkind,
spillSet, reloadSet, killSet
} =
let
(* Must do this to make sure the interference graph is
* reflected to the cells
*)
val _ = Core.updateCellAliases G
val getSpillLoc = Core.spillLoc G
fun spillLocOf(CB.CELL{id, ...}) = getSpillLoc id
val spillLocsOf = map spillLocOf
val getnode = IntHashTable.lookup nodes
val getnode = fn CB.CELL{id, ...} => getnode id
val insnDefUse = P.defUse cellkind
(* Merge prohibited registers *)
val enterSpill = IntHashTable.insert spilledRegs
val addProh = app (fn c => enterSpill(CellsBasis.registerId c,true))
val getSpills = G.PPtHashTable.find spillSet
val getSpills = fn p => case getSpills p of SOME s => s | NONE => []
val getReloads = G.PPtHashTable.find reloadSet
val getReloads = fn p => case getReloads p of SOME s => s | NONE => []
val getKills = G.PPtHashTable.find killSet
val getKills = fn p => case getKills p of SOME s => s | NONE => []
fun getLoc(G.NODE{color=ref(G.ALIASED n), ...}) = getLoc n
| getLoc(G.NODE{color=ref(G.MEMREG(_, m)), ...}) = G.MEM_REG m
| getLoc(G.NODE{color=ref(G.SPILL_LOC s), ...}) = G.FRAME s
| getLoc(G.NODE{color=ref(G.SPILLED), number, ...}) = G.FRAME number
| getLoc(G.NODE{color=ref(G.PSEUDO), number, ...}) = G.FRAME number
| getLoc _ = error "getLoc"
fun printRegs regs =
app (fn r => print(CellsBasis.toString r^" ["^
Core.spillLocToString G (CellsBasis.cellId r)^"] ")) regs
val parallelCopies = Word.andb(Core.HAS_PARALLEL_COPIES, mode) <> 0w0
fun chase(CB.CELL{col=ref(CB.ALIASED c), ...}) = chase c
| chase c = c
fun cellId(CB.CELL{id, ...}) = id
fun sameCell(CB.CELL{id=x,...}, CB.CELL{id=y, ...}) = x=y
fun same(x,regToSpill) = sameCell(chase x,regToSpill)
(*
* Rewrite the instruction given that a bunch of registers have
* to be spilled and reloaded.
*)
fun spillRewrite{pt, instrs, annotations} =
let
(*
* Insert reloading code for an instruction.
* Note: reload code goes after the instruction, if any.
*)
fun reloadInstr(instr,regToSpill,spillLoc) =
let val {code, proh, newReg} =
reload{instr=instr,reg=regToSpill,
spillLoc=spillLoc,annotations=annotations}
in addProh(proh);
code
end
(*
* Renaming the source for an instruction.
*)
fun renameInstr(instr,regToSpill,toSrc) =
let val {code, proh, newReg} =
renameSrc{instr=instr, fromSrc=regToSpill,toSrc=toSrc}
in addProh(proh);
code
end
(*
* Remove uses of regToSpill from a set of parallel copies.
* If there are multiple uses, then return multiple moves.
*)
fun extractUses(regToSpill, rds, rss) =
let fun loop(rd::rds, rs::rss, newRds, rds', rss') =
if same(rs,regToSpill) then
loop(rds, rss, rd::newRds, rds', rss')
else
loop(rds, rss, newRds, rd::rds', rs::rss')
| loop(_, _, newRds, rds', rss') = (newRds, rds', rss')
in loop(rds, rss, [], [], []) end
(*
* Insert reload code for the sources of a copy.
* Transformation:
* d1..dn <- s1..sn
* =>
* d1..dn/r <- s1...sn/r.
* reload code
* reload copies
*
*)
fun reloadCopySrc(instr,regToSpill,spillLoc) =
let val (dst, src) = P.moveDstSrc instr
val (rds, copyDst, copySrc) = extractUses(regToSpill, dst, src)
fun processMoves([], reloadCode) = reloadCode
| processMoves(rd::rds, reloadCode) =
let val code =
reloadDst{spillLoc=spillLoc,reg=regToSpill,
dst=rd,annotations=annotations}
in processMoves(rds, code@reloadCode)
end
val reloadCode = processMoves(rds, [])
in case copyDst of
[] => reloadCode
| _ => copyInstr((copyDst, copySrc), instr) @ reloadCode
end
(*
* Insert reload code
*)
fun reload(instr,regToSpill,spillLoc) =
if P.moveInstr instr then
reloadCopySrc(instr,regToSpill,spillLoc)
else
reloadInstr(instr,regToSpill,spillLoc)
(*
* Check whether the id is in a list
*)
fun containsId(id,[]) = false
| containsId(id:CB.cell_id,r::rs) = r = id orelse containsId(id,rs)
fun spillConflict(G.FRAME loc, rs) = containsId(~loc, rs)
| spillConflict(G.MEM_REG(CB.CELL{id, ...}), rs) =
containsId(id, rs)
fun contains(r',[]) = false
| contains(r',r::rs) = sameCell(r',r) orelse contains(r',rs)
(*
* Insert spill code for an instruction.
* Spill code occur after the instruction.
* If the value in regToSpill is never used, the client also
* has the opportunity to remove the instruction.
*)
fun spillInstr(instr,regToSpill,spillLoc,kill) =
let val {code, proh, newReg} =
spill{instr=instr,
kill=kill, spillLoc=spillLoc,
reg=regToSpill, annotations=annotations}
in addProh(proh);
code
end
(* Remove the definition regToSpill <- from
* parallel copies rds <- rss.
* Note, there is a guarantee that regToSpill is not aliased
* to another register in the rds set.
*)
fun extractDef(regToSpill,rds,rss,kill) =
let fun loop(rd::rds, rs::rss, rds', rss') =
if spillLocOf rd = spillLocOf rs then
(rs, rds@rds', rss@rss', true)
else if same(rd, regToSpill) then
(rs, rds@rds', rss@rss', kill)
else loop(rds, rss, rd::rds', rs::rss')
| loop _ =
(print("rds=");
app (fn r => print(CellsBasis.toString r^":"^
i2s(spillLocOf r)^" ")) rds;
print("\nrss=");
app (fn r => print(CellsBasis.toString r^":"^
i2s(spillLocOf r)^" ")) rss;
print "\n";
error("extractDef: "^CellsBasis.toString regToSpill))
in loop(rds, rss, [], []) end
(*
* Insert spill code for a destination of a copy
* suppose d = r and we have a copy d <- s in
* d1...dn <- s1...sn
*
* d1...dn <- s1...sn
* =>
* spill s to spillLoc
* d1...dn/d <- s1...sn/s
*
* However, if the spill code may ovewrite the spill location
* shared by other uses, we do the following less
* efficient scheme:
*
* /* save the result of d */
* d1...dn, tmp <- s1...sn, s
* spill tmp to spillLoc /* spill d */
*
*)
fun spillCopyDst(instr,regToSpill,spillLoc,kill,don'tOverwrite) =
let val (dst, src) = P.moveDstSrc instr
val (mvSrc,copyDst,copySrc,kill) =
extractDef(regToSpill,dst,src,kill)
val copy = case copyDst of
[] => []
| _ => copyInstr((copyDst,copySrc),instr)
in
if kill andalso not(!keep_dead_copies)
then (* kill the move *)
((* print ("Copy "^Int.toString(hd mvDst)^" <- "^
Int.toString(hd mvSrc)^" removed\n"); *)
copy
)
else (* normal spill *)
if spillConflict(spillLoc, don'tOverwrite) then
let (* cycle found *)
(*val _ = print("Register r"^Int.toString regToSpill^
" overwrites ["^Int.toString spillLoc^"]\n")*)
val tmp = C.newVar regToSpill (* new temporary *)
val copy = copyInstr((tmp::copyDst, mvSrc::copySrc),
instr)
val spillCode = spillSrc{src=tmp,reg=regToSpill,
spillLoc=spillLoc,
annotations=annotations}
in copy @ spillCode
end
else
let (* spill the move instruction *)
val spillCode = spillSrc{src=mvSrc,reg=regToSpill,
spillLoc=spillLoc,
annotations=annotations}
in spillCode @ copy
end
end
(*
* Insert spill code for a copy
*)
fun spillCopy(instr,regToSpill,spillLoc,kill,don'tOverwrite) =
case P.moveTmpR instr of
NONE => spillCopyDst(instr,regToSpill,spillLoc,kill,
don'tOverwrite)
| SOME tmp =>
if same(tmp, regToSpill)
then ((* spilledCopyTmps := !spilledCopyTmps + 1; *)
[spillCopyTmp{copy=instr, reg=regToSpill,
spillLoc=spillLoc,
annotations=annotations}])
else spillCopyDst(instr,regToSpill,spillLoc,kill,
don'tOverwrite)
(*
* Insert spill code
*)
fun spill(instr,regToSpill,spillLoc,killSet,don'tOverwrite) =
let val kill = contains(regToSpill,killSet)
in if P.moveInstr instr then
spillCopy(instr,regToSpill,spillLoc,kill,don'tOverwrite)
else
spillInstr(instr,regToSpill,spillLoc,kill)
end
fun contains([],reg) = false
| contains(r::rs,reg) = same(r,reg) orelse contains(rs,reg)
fun hasDef(i,reg) = contains(#1(insnDefUse i),reg)
fun hasUse(i,reg) = contains(#2(insnDefUse i),reg)
fun spillOneReg([],_,_,_,_) = []
| spillOneReg(i::instrs,r,spillLoc,killSet,don'tOverwrite) =
if hasDef(i,r)
then
spillOneReg(spill(i,r,spillLoc,killSet,don'tOverwrite)@instrs,
r,spillLoc,killSet,don'tOverwrite)
else i::spillOneReg(instrs,r,spillLoc,killSet,don'tOverwrite)
fun reloadOneReg([],_,_) = []
| reloadOneReg(i::instrs,r,spillLoc) =
if hasUse(i,r)
then reloadOneReg(reload(i,r,spillLoc)@instrs,
r,spillLoc)
else i::reloadOneReg(instrs,r,spillLoc)
(* This function spills a set of registers for an instruction *)
fun spillAll(instrs,[],killSet,don'tOverwrite) = instrs
| spillAll(instrs,r::rs,killSet,don'tOverwrite) =
let val node = getnode r
val spillLoc = getLoc node
in spillAll(
spillOneReg(instrs,r,spillLoc,killSet,don'tOverwrite),
rs,killSet,don'tOverwrite)
end
(* This function reloads a set of registers for an instruction *)
fun reloadAll(instrs,[]) = instrs
| reloadAll(instrs,r::rs) =
let val node = getnode r
val spillLoc = getLoc node
in reloadAll(reloadOneReg(instrs,r,spillLoc),rs)
end
fun loop([], pt, newInstrs) = newInstrs
| loop(instr::rest, pt, newInstrs) =
let val spillRegs = getSpills pt
val reloadRegs = getReloads pt
in case (spillRegs, reloadRegs) of
([], []) => loop(rest, dec pt, instr::newInstrs)
| _ =>
(* Eliminate duplicates from the spill/reload candidates *)
let val killRegs = getKills pt
val spillRegs = uniq spillRegs
val reloadRegs = uniq reloadRegs
(* spill locations that we can't overwrite if we
* are spilling a parallel copy
*)
val don'tOverwrite =
if parallelCopies then spillLocsOf reloadRegs
else []
val instrs = spillAll([instr],spillRegs,killRegs,
don'tOverwrite)
val _ = if debug then
(print("pt="^pt2s pt^"\n");
case spillRegs of
[] => ()
| _ => (print("Spilling ");
printRegs spillRegs;
print "\n");
case reloadRegs of
[] => ()
| _ => (print("Reloading ");
printRegs reloadRegs;
print "\n");
print "Before:"; emit instr
) else ()
val instrs = reloadAll(instrs,reloadRegs)
val _ = if debug then
(print "After:"; app emit instrs;
print "------------------\n")
else ()
fun concat([], l) = l
| concat(a::b, l) = concat(b, a::l)
in loop(rest, dec pt, concat(instrs, newInstrs))
end
end
in loop(rev instrs, pt, [])
end
in spillRewrite
end
end
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