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wasm: align heap to 16 bytes #2014

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Merged
merged 1 commit into from
Jul 30, 2021
Merged

wasm: align heap to 16 bytes #2014

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6 changes: 4 additions & 2 deletions src/runtime/arch_tinygowasm.go
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Original file line number Diff line number Diff line change
Expand Up @@ -32,9 +32,11 @@ var (

const wasmPageSize = 64 * 1024

// Align on word boundary.
func align(ptr uintptr) uintptr {
return (ptr + 3) &^ 3
// Align to 16, which is the alignment of max_align_t:
// https://godbolt.org/z/dYqTsWrGq
const heapAlign = 16
return (ptr + heapAlign - 1) &^ (heapAlign - 1)
}

func getCurrentStackPointer() uintptr
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8 changes: 8 additions & 0 deletions src/runtime/gc_conservative.go
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Expand Up @@ -228,6 +228,14 @@ func setHeapEnd(newHeapEnd uintptr) {
// This function can be called again when the heap size increases. The caller is
// responsible for copying the metadata to the new location.
func calculateHeapAddresses() {
if GOARCH == "wasm" {
// This is a workaround for a bug in wasm-ld: wasm-ld doesn't always
// align __heap_base and when this memory is shared through an API, it
// might result in unaligned memory. For details, see:
// https://reviews.llvm.org/D106499
// It should be removed once we switch to LLVM 13, where this is fixed.
heapStart = align(heapStart)
}
totalSize := heapEnd - heapStart

// Allocate some memory to keep 2 bits of information about every block.
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