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Handle blocks larger than MAXSIZE in TLSF #1763

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Merged
merged 2 commits into from
Mar 29, 2021
Merged

Handle blocks larger than MAXSIZE in TLSF #1763

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ec114ba
Handle blocks larger than MAXSIZE in TLSF
dcodeIO Mar 28, 2021
1d9a811
fold slightly
dcodeIO Mar 29, 2021
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40 changes: 17 additions & 23 deletions std/assembly/rt/tlsf.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -207,36 +207,30 @@ function insertBlock(root: Root, block: Block): void {

// merge with right block if also free
if (rightInfo & FREE) {
let newSize = (blockInfo & ~TAGS_MASK) + BLOCK_OVERHEAD + (rightInfo & ~TAGS_MASK);
if (newSize < BLOCK_MAXSIZE) {
removeBlock(root, right);
block.mmInfo = blockInfo = (blockInfo & TAGS_MASK) | newSize;
right = GETRIGHT(block);
rightInfo = right.mmInfo;
// 'back' is set below
}
removeBlock(root, right);
block.mmInfo = blockInfo = blockInfo + BLOCK_OVERHEAD + (rightInfo & ~TAGS_MASK); // keep block tags
right = GETRIGHT(block);
rightInfo = right.mmInfo;
// 'back' is set below
}

// merge with left block if also free
if (blockInfo & LEFTFREE) {
let left = GETFREELEFT(block);
let leftInfo = left.mmInfo;
if (DEBUG) assert(leftInfo & FREE); // must be free according to right tags
let newSize = (leftInfo & ~TAGS_MASK) + BLOCK_OVERHEAD + (blockInfo & ~TAGS_MASK);
if (newSize < BLOCK_MAXSIZE) {
removeBlock(root, left);
left.mmInfo = blockInfo = (leftInfo & TAGS_MASK) | newSize;
block = left;
// 'back' is set below
}
removeBlock(root, left);
block = left;
block.mmInfo = blockInfo = leftInfo + BLOCK_OVERHEAD + (blockInfo & ~TAGS_MASK); // keep left tags
// 'back' is set below
}

right.mmInfo = rightInfo | LEFTFREE;
// reference to right is no longer used now, hence rightInfo is not synced

// we now know the size of the block
var size = blockInfo & ~TAGS_MASK;
if (DEBUG) assert(size >= BLOCK_MINSIZE && size < BLOCK_MAXSIZE); // must be a valid size
if (DEBUG) assert(size >= BLOCK_MINSIZE); // must be a valid size
if (DEBUG) assert(changetype<usize>(block) + BLOCK_OVERHEAD + size == changetype<usize>(right)); // must match

// set 'back' to itself at the end of block
Expand All @@ -249,8 +243,9 @@ function insertBlock(root: Root, block: Block): void {
sl = <u32>(size >> AL_BITS);
} else {
const inv: usize = sizeof<usize>() * 8 - 1;
fl = inv - clz<usize>(size);
sl = <u32>((size >> (fl - SL_BITS)) ^ (1 << SL_BITS));
let boundedSize = min(size, BLOCK_MAXSIZE);
fl = inv - clz<usize>(boundedSize);
sl = <u32>((boundedSize >> (fl - SL_BITS)) ^ (1 << SL_BITS));
fl -= SB_BITS - 1;
}
if (DEBUG) assert(fl < FL_BITS && sl < SL_SIZE); // fl/sl out of range
Expand All @@ -272,7 +267,7 @@ function removeBlock(root: Root, block: Block): void {
var blockInfo = block.mmInfo;
if (DEBUG) assert(blockInfo & FREE); // must be free
var size = blockInfo & ~TAGS_MASK;
if (DEBUG) assert(size >= BLOCK_MINSIZE && size < BLOCK_MAXSIZE); // must be valid
if (DEBUG) assert(size >= BLOCK_MINSIZE); // must be valid

// mapping_insert
var fl: usize, sl: u32;
Expand All @@ -281,8 +276,9 @@ function removeBlock(root: Root, block: Block): void {
sl = <u32>(size >> AL_BITS);
} else {
const inv: usize = sizeof<usize>() * 8 - 1;
fl = inv - clz<usize>(size);
sl = <u32>((size >> (fl - SL_BITS)) ^ (1 << SL_BITS));
let boundedSize = min(size, BLOCK_MAXSIZE);
fl = inv - clz<usize>(boundedSize);
sl = <u32>((boundedSize >> (fl - SL_BITS)) ^ (1 << SL_BITS));
fl -= SB_BITS - 1;
}
if (DEBUG) assert(fl < FL_BITS && sl < SL_SIZE); // fl/sl out of range
Expand Down Expand Up @@ -528,8 +524,6 @@ export function reallocateBlock(root: Root, block: Block, size: usize): Block {
let mergeSize = blockSize + BLOCK_OVERHEAD + (rightInfo & ~TAGS_MASK);
if (mergeSize >= payloadSize) {
removeBlock(root, right);
// TODO: this can yield an intermediate block larger than BLOCK_MAXSIZE, which
// is immediately split though. does this trigger any assertions / issues?
block.mmInfo = (blockInfo & TAGS_MASK) | mergeSize;
prepareBlock(root, block, payloadSize);
if (isDefined(ASC_RTRACE)) onresize(block, BLOCK_OVERHEAD + blockSize);
Expand Down
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