tinygo-org/tinygo
1
0
Fork 0
mirror of https://github.com/tinygo-org/tinygo.git synced 2026-08-16 18:53:29 +00:00
Code Issues Packages Projects Releases 6 Wiki Activity

src/runtime: make hashmap calculations more uintptr-size independent

Browse Source
This commit is contained in:
Damian Gryski
2022-04-09 18:59:44 -07:00
committed by Ron Evans
parent 8b360ec911
commit 1abe1203a3
1 changed files with 14 additions and 19 deletions
Download Patch File Download Diff File Expand all files Collapse all files
src/runtime/hashmap.go
+14 -19
View File
@@ -109,27 +109,22 @@ func hashmapKeyHashAlg(alg hashmapAlgorithm) func(key unsafe.Pointer, n uintptr)
} }
func hashmapShouldGrow(m *hashmap) bool { func hashmapShouldGrow(m *hashmap) bool {
// with 29 bucket bits, we have potentially 8*(1 << 29) == 2^32 elements if m.bucketBits > uint8((unsafe.Sizeof(uintptr(0))*8)-3) {
if m.bucketBits <= 29 { // Over this limit, we're likely to overflow uintptrs during calculations
// "maximum" number of elements is 0.75 * buckets * elements per bucket // or numbers of hash elements. Don't allow any more growth.
// to avoid overflow, this is calculated as // With 29 bits, this is 2^32 elements anyway.
// max = 3 * (1/4 * buckets * elements per bucket) return false
// = 3 * (buckets * (elements per bucket)/4)
// = 3 * (buckets * (8/4)
// = 3 * (buckets * 2)
// = 6 * buckets
max := (uintptr(6) << m.bucketBits)
return m.count > max
} }
if m.bucketBits == 30 && m.count > uintptr(0xe0000000) { // "maximum" number of elements is 0.75 * buckets * elements per bucket
return true // to avoid overflow, this is calculated as
} // max = 3 * (1/4 * buckets * elements per bucket)
// = 3 * (buckets * (elements per bucket)/4)
// bucketBits == 32 will cause overflow problems on 32-bit platforms, so we limit it to 31. // = 3 * (buckets * (8/4)
// We're also likely to overflow the `int`-sized map length, causing other issues. // = 3 * (buckets * 2)
// = 6 * buckets
return false max := (uintptr(6) << m.bucketBits)
return m.count > max
} }
// Return the number of entries in this hashmap, called from the len builtin. // Return the number of entries in this hashmap, called from the len builtin.