GHC/CmmToAsm/X86/Regs.hs

    {-# LANGUAGE CPP #-}

    module GHC.CmmToAsm.X86.Regs (
            -- squeese functions for the graph allocator
            virtualRegSqueeze,
            realRegSqueeze,

            -- immediates
            Imm(..),
            strImmLit,
            litToImm,

            -- addressing modes
            AddrMode(..),
            addrOffset,

            -- registers
            spRel,
            argRegs,
            allArgRegs,
            allIntArgRegs,
            callClobberedRegs,
            instrClobberedRegs,
            allMachRegNos,
            classOfRealReg,
            showReg,

            -- machine specific
            EABase(..), EAIndex(..), addrModeRegs,

            eax, ebx, ecx, edx, esi, edi, ebp, esp,

            rax, rbx, rcx, rdx, rsi, rdi, rbp, rsp,
            r8,  r9,  r10, r11, r12, r13, r14, r15,
            lastint,
            xmm0, xmm1, xmm2, xmm3, xmm4, xmm5, xmm6, xmm7,
            xmm8, xmm9, xmm10, xmm11, xmm12, xmm13, xmm14, xmm15,
            xmm,
            firstxmm, lastxmm,

            ripRel,
            allFPArgRegs,

            allocatableRegs
    )

    where

    #include "HsVersions.h"

    import GHC.Prelude

    import GHC.Platform.Regs
    import GHC.Platform.Reg
    import GHC.Platform.Reg.Class

    import GHC.Cmm
    import GHC.Cmm.CLabel           ( CLabel )
    import GHC.Utils.Outputable
    import GHC.Platform

    import qualified Data.Array as A

    -- | regSqueeze_class reg
    --      Calculate the maximum number of register colors that could be
    --      denied to a node of this class due to having this reg
    --      as a neighbour.
    --
    {-# INLINE virtualRegSqueeze #-}
    virtualRegSqueeze :: RegClass -> VirtualReg -> Int

    virtualRegSqueeze cls vr
     = case cls of
            RcInteger
             -> case vr of
                    VirtualRegI{}           -> 1
                    VirtualRegHi{}          -> 1
                    _other                  -> 0

            RcDouble
             -> case vr of
                    VirtualRegD{}           -> 1
                    VirtualRegF{}           -> 0
                    _other                  -> 0

            _other -> 0

    {-# INLINE realRegSqueeze #-}
    realRegSqueeze :: RegClass -> RealReg -> Int
    realRegSqueeze cls rr
     = case cls of
            RcInteger
             -> case rr of
                    RealRegSingle regNo
                            | regNo < firstxmm -> 1
                            | otherwise     -> 0

                    RealRegPair{}           -> 0

            RcDouble
             -> case rr of
                    RealRegSingle regNo
                            | regNo >= firstxmm  -> 1
                            | otherwise     -> 0

                    RealRegPair{}           -> 0

            _other -> 0

    -- -----------------------------------------------------------------------------
    -- Immediates

    data Imm
      = ImmInt      Int
      | ImmInteger  Integer     -- Sigh.
      | ImmCLbl     CLabel      -- AbstractC Label (with baggage)
      | ImmLit      SDoc        -- Simple string
      | ImmIndex    CLabel Int
      | ImmFloat    Rational
      | ImmDouble   Rational
      | ImmConstantSum Imm Imm
      | ImmConstantDiff Imm Imm

    strImmLit :: String -> Imm
    strImmLit s = ImmLit (text s)

    litToImm :: CmmLit -> Imm
    litToImm (CmmInt i w)        = ImmInteger (narrowS w i)
                    -- narrow to the width: a CmmInt might be out of
                    -- range, but we assume that ImmInteger only contains
                    -- in-range values.  A signed value should be fine here.
    litToImm (CmmFloat f W32)    = ImmFloat f
    litToImm (CmmFloat f W64)    = ImmDouble f
    litToImm (CmmLabel l)        = ImmCLbl l
    litToImm (CmmLabelOff l off) = ImmIndex l off
    litToImm (CmmLabelDiffOff l1 l2 off _)
                                 = ImmConstantSum
                                   (ImmConstantDiff (ImmCLbl l1) (ImmCLbl l2))
                                   (ImmInt off)
    litToImm _                   = panic "X86.Regs.litToImm: no match"

    -- addressing modes ------------------------------------------------------------

    data AddrMode
            = AddrBaseIndex EABase EAIndex Displacement
            | ImmAddr Imm Int

    data EABase       = EABaseNone  | EABaseReg Reg | EABaseRip
    data EAIndex      = EAIndexNone | EAIndex Reg Int
    type Displacement = Imm

    addrOffset :: AddrMode -> Int -> Maybe AddrMode
    addrOffset addr off
      = case addr of
          ImmAddr i off0      -> Just (ImmAddr i (off0 + off))

          AddrBaseIndex r i (ImmInt n) -> Just (AddrBaseIndex r i (ImmInt (n + off)))
          AddrBaseIndex r i (ImmInteger n)
            -> Just (AddrBaseIndex r i (ImmInt (fromInteger (n + toInteger off))))

          AddrBaseIndex r i (ImmCLbl lbl)
            -> Just (AddrBaseIndex r i (ImmIndex lbl off))

          AddrBaseIndex r i (ImmIndex lbl ix)
            -> Just (AddrBaseIndex r i (ImmIndex lbl (ix+off)))

          _ -> Nothing  -- in theory, shouldn't happen

    addrModeRegs :: AddrMode -> [Reg]
    addrModeRegs (AddrBaseIndex b i _) =  b_regs ++ i_regs
      where
       b_regs = case b of { EABaseReg r -> [r]; _ -> [] }
       i_regs = case i of { EAIndex r _ -> [r]; _ -> [] }
    addrModeRegs _ = []

    -- registers -------------------------------------------------------------------

    -- @spRel@ gives us a stack relative addressing mode for volatile
    -- temporaries and for excess call arguments.  @fpRel@, where
    -- applicable, is the same but for the frame pointer.

    spRel :: Platform
          -> Int -- ^ desired stack offset in bytes, positive or negative
          -> AddrMode
    spRel platform n
     | target32Bit platform
        = AddrBaseIndex (EABaseReg esp) EAIndexNone (ImmInt n)
     | otherwise
        = AddrBaseIndex (EABaseReg rsp) EAIndexNone (ImmInt n)

    -- The register numbers must fit into 32 bits on x86, so that we can
    -- use a Word32 to represent the set of free registers in the register
    -- allocator.

    firstxmm :: RegNo
    firstxmm  = 16

    --  on 32bit platformOSs, only the first 8 XMM/YMM/ZMM registers are available
    lastxmm :: Platform -> RegNo
    lastxmm platform
     | target32Bit platform = firstxmm + 7  -- xmm0 - xmmm7
     | otherwise            = firstxmm + 15 -- xmm0 -xmm15

    lastint :: Platform -> RegNo
    lastint platform
     | target32Bit platform = 7 -- not %r8..%r15
     | otherwise            = 15

    intregnos :: Platform -> [RegNo]
    intregnos platform = [0 .. lastint platform]

    xmmregnos :: Platform -> [RegNo]
    xmmregnos platform = [firstxmm  .. lastxmm platform]

    floatregnos :: Platform -> [RegNo]
    floatregnos platform = xmmregnos platform

    -- argRegs is the set of regs which are read for an n-argument call to C.
    -- For archs which pass all args on the stack (x86), is empty.
    -- Sparc passes up to the first 6 args in regs.
    argRegs :: RegNo -> [Reg]
    argRegs _       = panic "MachRegs.argRegs(x86): should not be used!"

    -- | The complete set of machine registers.
    allMachRegNos :: Platform -> [RegNo]
    allMachRegNos platform = intregnos platform ++ floatregnos platform

    -- | Take the class of a register.
    {-# INLINE classOfRealReg #-}
    classOfRealReg :: Platform -> RealReg -> RegClass
    -- On x86, we might want to have an 8-bit RegClass, which would
    -- contain just regs 1-4 (the others don't have 8-bit versions).
    -- However, we can get away without this at the moment because the
    -- only allocatable integer regs are also 8-bit compatible (1, 3, 4).
    classOfRealReg platform reg
        = case reg of
            RealRegSingle i
                | i <= lastint platform -> RcInteger
                | i <= lastxmm platform -> RcDouble
                | otherwise             -> panic "X86.Reg.classOfRealReg registerSingle too high"
            _   -> panic "X86.Regs.classOfRealReg: RegPairs on this arch"

    -- | Get the name of the register with this number.
    -- NOTE: fixme, we dont track which "way" the XMM registers are used
    showReg :: Platform -> RegNo -> String
    showReg platform n
            | n >= firstxmm && n <= lastxmm  platform = "%xmm" ++ show (n-firstxmm)
            | n >= 8   && n < firstxmm      = "%r" ++ show n
            | otherwise      = regNames platform A.! n

    regNames :: Platform -> A.Array Int String
    regNames platform
        = if target32Bit platform
          then A.listArray (0,8) ["%eax", "%ebx", "%ecx", "%edx", "%esi", "%edi", "%ebp", "%esp"]
          else A.listArray (0,8) ["%rax", "%rbx", "%rcx", "%rdx", "%rsi", "%rdi", "%rbp", "%rsp"]

    -- machine specific ------------------------------------------------------------

    {-
    Intel x86 architecture:
    - All registers except 7 (esp) are available for use.
    - Only ebx, esi, edi and esp are available across a C call (they are callee-saves).
    - Registers 0-7 have 16-bit counterparts (ax, bx etc.)
    - Registers 0-3 have 8 bit counterparts (ah, bh etc.)

    The fp registers are all Double registers; we don't have any RcFloat class
    regs.  @regClass@ barfs if you give it a VirtualRegF, and mkVReg above should
    never generate them.

    TODO: cleanup modelling float vs double registers and how they are the same class.
    -}

    eax, ebx, ecx, edx, esp, ebp, esi, edi :: Reg

    eax   = regSingle 0
    ebx   = regSingle 1
    ecx   = regSingle 2
    edx   = regSingle 3
    esi   = regSingle 4
    edi   = regSingle 5
    ebp   = regSingle 6
    esp   = regSingle 7

    {-
    AMD x86_64 architecture:
    - All 16 integer registers are addressable as 8, 16, 32 and 64-bit values:

      8     16    32    64
      ---------------------
      al    ax    eax   rax
      bl    bx    ebx   rbx
      cl    cx    ecx   rcx
      dl    dx    edx   rdx
      sil   si    esi   rsi
      dil   si    edi   rdi
      bpl   bp    ebp   rbp
      spl   sp    esp   rsp
      r10b  r10w  r10d  r10
      r11b  r11w  r11d  r11
      r12b  r12w  r12d  r12
      r13b  r13w  r13d  r13
      r14b  r14w  r14d  r14
      r15b  r15w  r15d  r15
    -}

    rax, rbx, rcx, rdx, rsp, rbp, rsi, rdi,
      r8, r9, r10, r11, r12, r13, r14, r15,
      xmm0, xmm1, xmm2, xmm3, xmm4, xmm5, xmm6, xmm7,
      xmm8, xmm9, xmm10, xmm11, xmm12, xmm13, xmm14, xmm15 :: Reg

    rax   = regSingle 0
    rbx   = regSingle 1
    rcx   = regSingle 2
    rdx   = regSingle 3
    rsi   = regSingle 4
    rdi   = regSingle 5
    rbp   = regSingle 6
    rsp   = regSingle 7
    r8    = regSingle 8
    r9    = regSingle 9
    r10   = regSingle 10
    r11   = regSingle 11
    r12   = regSingle 12
    r13   = regSingle 13
    r14   = regSingle 14
    r15   = regSingle 15
    xmm0  = regSingle 16
    xmm1  = regSingle 17
    xmm2  = regSingle 18
    xmm3  = regSingle 19
    xmm4  = regSingle 20
    xmm5  = regSingle 21
    xmm6  = regSingle 22
    xmm7  = regSingle 23
    xmm8  = regSingle 24
    xmm9  = regSingle 25
    xmm10 = regSingle 26
    xmm11 = regSingle 27
    xmm12 = regSingle 28
    xmm13 = regSingle 29
    xmm14 = regSingle 30
    xmm15 = regSingle 31

    ripRel :: Displacement -> AddrMode
    ripRel imm      = AddrBaseIndex EABaseRip EAIndexNone imm

     -- so we can re-use some x86 code:
    {-
    eax = rax
    ebx = rbx
    ecx = rcx
    edx = rdx
    esi = rsi
    edi = rdi
    ebp = rbp
    esp = rsp
    -}

    xmm :: RegNo -> Reg
    xmm n = regSingle (firstxmm+n)

    -- | these are the regs which we cannot assume stay alive over a C call.
    callClobberedRegs       :: Platform -> [Reg]
    -- caller-saves registers
    callClobberedRegs platform
     | target32Bit platform = [eax,ecx,edx] ++ map regSingle (floatregnos platform)
     | platformOS platform == OSMinGW32
       = [rax,rcx,rdx,r8,r9,r10,r11]
       -- Only xmm0-5 are caller-saves registers on 64bit windows.
       -- ( https://docs.microsoft.com/en-us/cpp/build/register-usage )
       -- For details check the Win64 ABI.
       ++ map xmm [0  .. 5]
     | otherwise
        -- all xmm regs are caller-saves
        -- caller-saves registers
        = [rax,rcx,rdx,rsi,rdi,r8,r9,r10,r11]
       ++ map regSingle (floatregnos platform)

    allArgRegs :: Platform -> [(Reg, Reg)]
    allArgRegs platform
     | platformOS platform == OSMinGW32 = zip [rcx,rdx,r8,r9]
                                              (map regSingle [firstxmm ..])
     | otherwise = panic "X86.Regs.allArgRegs: not defined for this arch"

    allIntArgRegs :: Platform -> [Reg]
    allIntArgRegs platform
     | (platformOS platform == OSMinGW32) || target32Bit platform
        = panic "X86.Regs.allIntArgRegs: not defined for this platform"
     | otherwise = [rdi,rsi,rdx,rcx,r8,r9]

    -- | on 64bit platforms we pass the first 8 float/double arguments
    -- in the xmm registers.
    allFPArgRegs :: Platform -> [Reg]
    allFPArgRegs platform
     | platformOS platform == OSMinGW32
        = panic "X86.Regs.allFPArgRegs: not defined for this platform"
     | otherwise = map regSingle [firstxmm .. firstxmm + 7 ]

    -- Machine registers which might be clobbered by instructions that
    -- generate results into fixed registers, or need arguments in a fixed
    -- register.
    instrClobberedRegs :: Platform -> [Reg]
    instrClobberedRegs platform
     | target32Bit platform = [ eax, ecx, edx ]
     | otherwise            = [ rax, rcx, rdx ]

    --

    -- allocatableRegs is allMachRegNos with the fixed-use regs removed.
    -- i.e., these are the regs for which we are prepared to allow the
    -- register allocator to attempt to map VRegs to.
    allocatableRegs :: Platform -> [RealReg]
    allocatableRegs platform
       = let isFree i = freeReg platform i
         in  map RealRegSingle $ filter isFree (allMachRegNos platform)