ghc-9.6.3: The GHC API

Safe Haskell | Safe-Inferred
Language | Haskell2010

GHC.CmmToAsm

Contents

- Test-only exports: see trac #12744

Description

Native code generator

The native-code generator has machine-independent and machine-dependent modules.

This module (GHC.CmmToAsm) is the top-level machine-independent module. Before entering machine-dependent land, we do some machine-independent optimisations (defined below) on the `CmmStmts`s.

We convert to the machine-specific `Instr` datatype with `cmmCodeGen`, assuming an infinite supply of registers. We then use a machine-independent register allocator (`regAlloc`) to rejoin reality. Obviously, `regAlloc` has machine-specific helper functions (see about RegAllocInfo below).

Finally, we order the basic blocks of the function so as to minimise the number of jumps between blocks, by utilising fallthrough wherever possible.

The machine-dependent bits break down as follows:

- [MachRegs] Everything about the target platform's machine registers (and immediate operands, and addresses, which tend to intermingle/interact with registers).
- [MachInstrs] Includes the `Instr` datatype (possibly should have a module of its own), plus a miscellany of other things (e.g., `targetDoubleSize`, `smStablePtrTable`, ...)
- [MachCodeGen] is where `Cmm` stuff turns into machine instructions.
- [PprMach] `pprInstr` turns an `Instr` into text (well, really a `SDoc`).
- [RegAllocInfo] In the register allocator, we manipulate `MRegsState`s, which are `BitSet`s, one bit per machine register. When we want to say something about a specific machine register (e.g., ``it gets clobbered by this instruction''), we set/unset its bit. Obviously, we do this `BitSet` thing for efficiency reasons.

The `RegAllocInfo` module collects together the machine-specific info needed to do register allocation.

- [RegisterAlloc] The (machine-independent) register allocator. -}

Synopsis

- nativeCodeGen :: forall a. Logger -> ToolSettings -> NCGConfig -> ModLocation -> Handle -> UniqSupply -> Stream IO RawCmmGroup a -> IO a
- cmmNativeGen :: forall statics instr jumpDest. (Instruction instr, OutputableP Platform statics, Outputable jumpDest) => Logger -> NcgImpl statics instr jumpDest -> UniqSupply -> DwarfFiles -> LabelMap DebugBlock -> RawCmmDecl -> Int -> IO (UniqSupply, DwarfFiles, [NatCmmDecl statics instr], [CLabel], Maybe [RegAllocStats statics instr], Maybe [RegAllocStats], LabelMap [UnwindPoint])
- data NcgImpl statics instr jumpDest = NcgImpl {
  - ncgConfig :: !NCGConfig
  - cmmTopCodeGen :: RawCmmDecl -> NatM [NatCmmDecl statics instr]
  - generateJumpTableForInstr :: instr -> Maybe (NatCmmDecl statics instr)
  - getJumpDestBlockId :: jumpDest -> Maybe BlockId
  - canShortcut :: instr -> Maybe jumpDest
  - shortcutStatics :: (BlockId -> Maybe jumpDest) -> statics -> statics
  - shortcutJump :: (BlockId -> Maybe jumpDest) -> instr -> instr
  - pprNatCmmDeclS :: NatCmmDecl statics instr -> SDoc
  - pprNatCmmDeclH :: NatCmmDecl statics instr -> HDoc
  - maxSpillSlots :: Int
  - allocatableRegs :: [RealReg]
  - ncgAllocMoreStack :: Int -> NatCmmDecl statics instr -> UniqSM (NatCmmDecl statics instr, [(BlockId, BlockId)])
  - ncgMakeFarBranches :: LabelMap RawCmmStatics -> [NatBasicBlock instr] -> [NatBasicBlock instr]
  - extractUnwindPoints :: [instr] -> [UnwindPoint]
  - invertCondBranches :: Maybe CFG -> LabelMap RawCmmStatics -> [NatBasicBlock instr] -> [NatBasicBlock instr]
  }

# Documentation

nativeCodeGen :: forall a. Logger -> ToolSettings -> NCGConfig -> ModLocation -> Handle -> UniqSupply -> Stream IO RawCmmGroup a -> IO a Source #

# Test-only exports: see trac #12744

cmmNativeGen Source #

Arguments

:: forall statics instr jumpDest. (Instruction instr, OutputableP Platform statics, Outputable jumpDest) |
=> Logger |
-> NcgImpl statics instr jumpDest |
-> UniqSupply |
-> DwarfFiles |
-> LabelMap DebugBlock |
-> RawCmmDecl | the cmm to generate code for
-> Int | sequence number of this top thing
-> IO (UniqSupply, DwarfFiles, [NatCmmDecl statics instr], [CLabel], Maybe [RegAllocStats statics instr], Maybe [RegAllocStats], LabelMap [UnwindPoint]) |

Complete native code generation phase for a single top-level chunk of Cmm. Dumping the output of each stage along the way. Global conflict graph and NGC stats

data NcgImpl statics instr jumpDest Source #

Constructors

NcgImpl |

Fields

- ncgConfig :: !NCGConfig
- cmmTopCodeGen :: RawCmmDecl -> NatM [NatCmmDecl statics instr]
- generateJumpTableForInstr :: instr -> Maybe (NatCmmDecl statics instr)
- getJumpDestBlockId :: jumpDest -> Maybe BlockId
- canShortcut :: instr -> Maybe jumpDest
- shortcutStatics :: (BlockId -> Maybe jumpDest) -> statics -> statics
- shortcutJump :: (BlockId -> Maybe jumpDest) -> instr -> instr
- pprNatCmmDeclS :: NatCmmDecl statics instr -> SDoc

  `GenModule` is only for printing internal labels. See Note [Internal proc labels] in CLabel.

- pprNatCmmDeclH :: NatCmmDecl statics instr -> HDoc
- maxSpillSlots :: Int
- allocatableRegs :: [RealReg]
- ncgAllocMoreStack :: Int -> NatCmmDecl statics instr -> UniqSM (NatCmmDecl statics instr, [(BlockId, BlockId)])

  The list of block ids records the redirected jumps to allow us to update the CFG.

- ncgMakeFarBranches :: LabelMap RawCmmStatics -> [NatBasicBlock instr] -> [NatBasicBlock instr]
- extractUnwindPoints :: [instr] -> [UnwindPoint]

  given the instruction sequence of a block, produce a list of the block's `UnwindPoint`s See Note [What is this unwinding business?] in GHC.Cmm.DebugBlock and Note [Unwinding information in the NCG] in this module.

- invertCondBranches :: Maybe CFG -> LabelMap RawCmmStatics -> [NatBasicBlock instr] -> [NatBasicBlock instr]

  Turn the sequence of `jcc l1; jmp l2` into `jncc l2; <block_l1>` when possible.