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Verific: guard large-mem RAM width/word-count against int overflow

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Address review feedback on the large-memory fix:
- comment explaining the 64-bit promotion and the remaining int limits
- log_error if the per-word width or word count would overflow RTLIL's
  int memory->width / memory->size fields, instead of silently truncating

Co-authored-by: Cursor <cursoragent@cursor.com>
This commit is contained in:
Akash Levy 2026-06-24 23:33:55 -07:00
parent 2c790e52cd
commit 2f8c9327b3
1 changed files with 17 additions and 0 deletions
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17
frontends/verific/verific.cc
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@ -1822,6 +1822,12 @@ void VerificImporter::import_netlist(RTLIL::Design *design, Netlist *nl, std::ma
module->memories[memory->name] = memory;
import_attributes(memory->attributes, net, nl);
// net->Size() returns a 64-bit count of the RAM's total bits. For very
// large memories this exceeds 2^31, so these running totals must be kept
// in 64-bit values; a 32-bit int would truncate (e.g. to 0), which then
// set memory->width to 0 and tripped log_assert(width != 0) in opt_mem.
// The final per-word width and word count still have to fit in RTLIL's
// int fields (memory->width / memory->size); that is checked below.
long long number_of_bits = net->Size();
long long min_bits_in_word = number_of_bits;
int max_bits_in_addr = 0;
@ -1846,6 +1852,17 @@ void VerificImporter::import_netlist(RTLIL::Design *design, Netlist *nl, std::ma
long long number_of_words = number_of_bits / min_bits_in_word;
// memory->width and memory->size are ints in RTLIL (and memory->size is
// later derived from int address bounds), so the per-word width and the
// word count must each fit in an int. Bail out rather than silently
// storing a truncated/corrupt value.
if (min_bits_in_word > INT_MAX)
log_error("Verific RamNet %s has a word width of %lld bits, which exceeds the maximum supported width of %d.\n",
net->Name(), (long long)min_bits_in_word, INT_MAX);
if (number_of_words > INT_MAX)
log_error("Verific RamNet %s has %lld words, which exceeds the maximum supported size of %d.\n",
net->Name(), (long long)number_of_words, INT_MAX);
memory->width = (int)min_bits_in_word;
memory->size = 0;
memory->start_offset = INT_MAX;