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scr1 test suite: processing passes get stuck, and allocate huge amounts of system RAM when verilog contains memory blocks #1286

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veripoolbot opened this issue Mar 8, 2018 · 4 comments
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scr1 test suite: processing passes get stuck, and allocate huge amounts of system RAM when verilog contains memory blocks #1286

veripoolbot opened this issue Mar 8, 2018 · 4 comments
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effort: days Expect this issue to require roughly days of invested effort to resolve

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Author Name: Joel Holdsworth
Original Redmine Issue: 1286 from https://www.veripool.org

Verilator gets stuck allocating huge amounts of memory when processing SystemVerilog code like this...

module test(input reset);

parameter MEM_POWER_SIZE = 16;
logic [7:0] memory [0:2**MEM_POWER_SIZE-1];

always @(negedge reset) begin
  memory = '{2**MEM_POWER_SIZE{'0}};
end

endmodule
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Original Redmine Comment
Author Name: Wilson Snyder (@wsnyder)
Original Date: 2018-03-09T04:45:02Z

Verilator needs enough memory to fit the entire model, times some inefficiency factor.

The fix could be to throw an error on very large structures (which of course should instead be sparse models), but it's hard to determine what is too large as that depends on system constraints. So my inclination is to leave it as is, but other ideas are welcome.

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Original Redmine Comment
Author Name: Joel Holdsworth
Original Date: 2018-03-09T17:10:54Z

It would be nice to get an error or a warning. I only figured out the source of the problem by reading the file & line-number out of the AST in gdb.

I could try making the RAM block smaller. At the moment it's allocating more system RAM than I have; at least 2Gb. I'm not sure to what extent the test suite relies on this block being the size it is.

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Original Redmine Comment
Author Name: Joel Holdsworth
Original Date: 2018-03-10T04:21:31Z

The block was 16Mb in size. Fortunately nothing in the test suite needs this much memory, so I reduced it to 64kB, and now Verilator is much happier

@veripoolbot veripoolbot added the effort: days Expect this issue to require roughly days of invested effort to resolve label Dec 22, 2019
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wsnyder commented May 27, 2023

Closing due to age; not sure what can be fixed here, if someone wants to contribute ideas or a patch please reopen.

@wsnyder wsnyder closed this as completed May 27, 2023
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