| Copyright | (c) The University of Glasgow 2001 |
|---|---|
| License | BSD-style (see the file LICENSE) |
| Maintainer | Jeffrey Young <jeffrey.young@iohk.io> Luite Stegeman <luite.stegeman@iohk.io> Sylvain Henry <sylvain.henry@iohk.io> Josh Meredith <josh.meredith@iohk.io> |
| Stability | experimental |
| Safe Haskell | None |
| Language | GHC2021 |
GHC.StgToJS.Stack
Contents
Description
Utilities and wrappers for Stack manipulation in JS Land.
In general, functions suffixed with a tick do the actual work, functions
suffixed with an I are identical to the non-I versions but work on Idents
The stack in JS land is held in the special JS array 'h$stack' and the stack pointer is held in 'h$sp'. The top of the stack thus exists at 'h$stack[h$sp]'. h$stack[h$sp + i] where i > 0, moves deeper into the stack into older entries, whereas h$stack[h$sp - i] moves towards the top of the stack.
The stack layout algorithm is slightly peculiar. It makes an effort to remember recently popped things so that if these values need to be pushed then they can be quickly. The implementation for this is storing these values above the stack pointer, and the pushing will skip slots that we know we will use and fill in slots marked as unknown. Thus, you may find that our push and pop functions do some non-traditional stack manipulation such as adding slots in pop or removing slots in push.
Synopsis
- resetSlots :: G a -> G a
- isolateSlots :: G a -> G a
- setSlots :: [StackSlot] -> G ()
- getSlots :: G [StackSlot]
- addSlots :: [StackSlot] -> G ()
- dropSlots :: Int -> G ()
- addUnknownSlots :: Int -> G ()
- push :: [JStgExpr] -> G JStgStat
- push' :: StgToJSConfig -> [JStgExpr] -> JStgStat
- adjSpN :: Int -> G JStgStat
- adjSpN' :: Int -> JStgStat
- adjSp' :: Int -> JStgStat
- adjSp :: Int -> G JStgStat
- pushNN :: Array Integer Ident
- pushNN' :: Array Integer JStgExpr
- pushN' :: Array Int JStgExpr
- pushN :: Array Int Ident
- pushOptimized' :: [(Id, Int)] -> G JStgStat
- pushOptimized :: [(JStgExpr, Bool)] -> G JStgStat
- pushLneFrame :: HasDebugCallStack => Int -> ExprCtx -> G JStgStat
- popN :: Int -> G JStgStat
- popSkip :: Int -> [JStgExpr] -> JStgStat
- popSkipI :: Int -> [(Ident, StackSlot)] -> G JStgStat
- loadSkip :: Int -> [JStgExpr] -> JStgStat
- updateThunk :: G JStgStat
- updateThunk' :: StgToJSConfig -> JStgStat
- bhStats :: StgToJSConfig -> Bool -> JStgStat
Documentation
resetSlots :: G a -> G a Source #
Run the action, m, with no stack info
isolateSlots :: G a -> G a Source #
run the action, m, with current stack info, but don't let modifications
propagate
addUnknownSlots :: Int -> G () Source #
add n unknown slots to our stack knowledge
adjSpN :: Int -> G JStgStat Source #
Shrink the stack and stack pointer. NB: This function is unsafe when the
input n, is negative. This function wraps around adjSpN which actually
performs the work.
adjSpN' :: Int -> JStgStat Source #
Shrink the stack pointer by n. The stack grows downward so substract
adjSp' :: Int -> JStgStat Source #
Grow the stack pointer by n without modifying the stack depth. The stack
is just a JS array so we add to grow (instead of the traditional subtract)
pushNN :: Array Integer Ident Source #
Partial Push functions. Like pushN except these push functions skip
slots. For example,
function h$pp33(x1, x2) {
h$sp += 6;
h$stack[(h$sp - 5)] = x1;
h$stack[(h$sp - 0)] = x2;
};
The 33rd entry skips slots 1-4 to bind the top of the stack and the 6th
slot. See pushOptimized and pushOptimized' for use cases.
pushN' :: Array Int JStgExpr Source #
Convert all function symbols in pushN to global top-level functions. This
is a hack which converts the function symbols to variables. This hack is
caught in prettyBlock' to turn these into global
functions.
pushN :: Array Int Ident Source #
A constant array that holds global function symbols which do N pushes onto
the stack. For example:
function h$p1(x1) {
++h$sp;
h$stack[(h$sp - 0)] = x1;
};
function h$p2(x1, x2) {
h$sp += 2;
h$stack[(h$sp - 1)] = x1;
h$stack[(h$sp - 0)] = x2;
};
and so on up to 32.
Arguments
| :: [(JStgExpr, Bool)] | contents of the slots, True if same value is already there |
| -> G JStgStat |
optimized push that reuses existing values on stack automatically chooses an optimized partial push (h$ppN) function when possible.
pushLneFrame :: HasDebugCallStack => Int -> ExprCtx -> G JStgStat Source #
push a let-no-escape frame onto the stack
Pop things, don't update the stack knowledge in G
loadSkip :: Int -> [JStgExpr] -> JStgStat Source #
Load 'length (xs :: [JStgExpr])' things from the stack at offset 'n :: Int'.
This function does no stack pointer manipulation, it merely indexes into the
stack and loads payloads into xs.
Thunk update
updateThunk :: G JStgStat Source #
Wrapper around updateThunk', performs the stack manipulation before
updating the Thunk.
updateThunk' :: StgToJSConfig -> JStgStat Source #
Update a thunk by checking StgToJSConfig. If the config inlines black
holes then update inline, else make an explicit call to the black hole
handler.