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author | Kartik Agaram <vc@akkartik.com> | 2018-06-25 13:39:19 -0700 |
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committer | Kartik Agaram <vc@akkartik.com> | 2018-06-25 13:39:19 -0700 |
commit | ad778b63d05a55d97e79bcf286a2c29264de15d7 (patch) | |
tree | bf9aafdc637d92530c5aab0ba345106d95c32219 /036abandon.cc | |
parent | 2caaa7f18f391995feae550c59fa175af86b6817 (diff) | |
download | mu-ad778b63d05a55d97e79bcf286a2c29264de15d7.tar.gz |
4273
Diffstat (limited to '036abandon.cc')
-rw-r--r-- | 036abandon.cc | 132 |
1 files changed, 132 insertions, 0 deletions
diff --git a/036abandon.cc b/036abandon.cc new file mode 100644 index 00000000..c2b9125e --- /dev/null +++ b/036abandon.cc @@ -0,0 +1,132 @@ +//: Reclaiming memory when it's no longer used. + +:(scenario new_reclaim) +def main [ + 10:&:num <- new number:type + 20:num <- deaddress 10:&:num + abandon 10:&:num + 30:&:num <- new number:type # must be same size as abandoned memory to reuse + 40:num <- deaddress 30:&:num + 50:bool <- equal 20:num, 40:num +] +# both allocations should have returned the same address ++mem: storing 1 in location 50 + +//: When abandoning addresses we'll save them to a 'free list', segregated by size. + +//: Before, suppose variable V contains address A which points to payload P: +//: location V contains an alloc-id N +//: location V+1 contains A +//: location A contains alloc-id N +//: location A+1 onwards contains P +//: Additionally, suppose the head of the free list is initially F. +//: After abandoning: +//: location V contains invalid alloc-id -1 +//: location V+1 contains 0 +//: location A contains invalid alloc-id N +//: location A+1 contains the previous head of free-list F + +:(before "End routine Fields") +map<int, int> free_list; + +:(before "End Primitive Recipe Declarations") +ABANDON, +:(before "End Primitive Recipe Numbers") +put(Recipe_ordinal, "abandon", ABANDON); +:(before "End Primitive Recipe Checks") +case ABANDON: { + if (!inst.products.empty()) { + raise << maybe(get(Recipe, r).name) << "'abandon' shouldn't write to any products in '" << to_original_string(inst) << "'\n" << end(); + break; + } + for (int i = 0; i < SIZE(inst.ingredients); ++i) { + if (!is_mu_address(inst.ingredients.at(i))) + raise << maybe(get(Recipe, r).name) << "ingredients of 'abandon' should be addresses, but ingredient " << i << " is '" << to_string(inst.ingredients.at(i)) << '\n' << end(); + break; + } + break; +} +:(before "End Primitive Recipe Implementations") +case ABANDON: { + for (int i = 0; i < SIZE(current_instruction().ingredients); ++i) { + reagent/*copy*/ ingredient = current_instruction().ingredients.at(i); + canonize(ingredient); + abandon(get_or_insert(Memory, ingredient.value+/*skip alloc id*/1), payload_size(ingredient)); +//? cerr << "clear after abandon: " << ingredient.value << '\n'; + put(Memory, /*alloc id*/ingredient.value, /*invalid*/-1); + put(Memory, /*address*/ingredient.value+1, 0); + } + break; +} + +:(code) +void abandon(int address, int payload_size) { + put(Memory, address, /*invalid alloc-id*/-1); +//? cerr << "abandon: " << address << '\n'; + // clear rest of payload + for (int curr = address+1; curr < address+payload_size; ++curr) + put(Memory, curr, 0); + // append existing free list to address + trace("abandon") << "saving " << address << " in free-list of size " << payload_size << end(); + put(Memory, address+/*skip invalid alloc-id*/1, get_or_insert(Current_routine->free_list, payload_size)); + put(Current_routine->free_list, payload_size, address); +} + +int payload_size(reagent/*copy*/ x) { + x.properties.push_back(pair<string, string_tree*>("lookup", NULL)); + lookup_memory_core(x, /*check_for_null*/false); + return size_of(x)+/*alloc id*/1; +} + +:(after "Allocate Special-cases") +if (get_or_insert(Current_routine->free_list, size)) { + trace("abandon") << "picking up space from free-list of size " << size << end(); + int result = get_or_insert(Current_routine->free_list, size); + trace("mem") << "new alloc from free list: " << result << end(); + put(Current_routine->free_list, size, get_or_insert(Memory, result+/*skip alloc id*/1)); + // clear 'deleted' tag + put(Memory, result, 0); + // clear next pointer + put(Memory, result+/*skip alloc id*/1, 0); + for (int curr = result; curr < result+size; ++curr) { + if (get_or_insert(Memory, curr) != 0) { + raise << maybe(current_recipe_name()) << "memory in free list was not zeroed out: " << curr << '/' << result << "; somebody wrote to us after free!!!\n" << end(); + break; // always fatal + } + } + return result; +} + +:(scenario new_differing_size_no_reclaim) +def main [ + 1:&:num <- new number:type + 2:num <- deaddress 1:&:num + abandon 1:&:num + 3:&:@:num <- new number:type, 2 # different size + 4:num <- deaddress 3:&:@:num + 5:bool <- equal 2:num, 4:num +] +# no reuse ++mem: storing 0 in location 5 + +:(scenario new_reclaim_array) +def main [ + 10:&:@:num <- new number:type, 2 + 20:num <- deaddress 10:&:@:num + abandon 10:&:@:num + 30:&:@:num <- new number:type, 2 # same size + 40:num <- deaddress 30:&:@:num + 50:bool <- equal 20:num, 40:num +] +# both calls to new returned identical addresses ++mem: storing 1 in location 50 + +:(scenario lookup_of_abandoned_address_raises_error) +% Hide_errors = true; +def main [ + 1:&:num <- new num:type + 3:&:num <- copy 1:&:num + abandon 1:&:num + 5:num/raw <- copy *3:&:num +] ++error: main: address is already abandoned in '5:num/raw <- copy *3:&:num' |