From da65e1e8d9552f64e1e03c08108ca0532719bbfe Mon Sep 17 00:00:00 2001 From: whitequark Date: Tue, 29 Jan 2019 02:24:00 +0000 Subject: write_verilog: correctly emit asynchronous transparent ports. This commit fixes two related issues: * For asynchronous ports, clock is no longer added to domain list. (This would lead to absurd constructs like `always @(posedge 0)`. * The logic to distinguish synchronous and asynchronous ports is changed to correctly use or avoid clock in all cases. Before this commit, the following RTLIL snippet (after memory_collect) cell $memrd $2 parameter \MEMID "\\mem" parameter \ABITS 2 parameter \WIDTH 4 parameter \CLK_ENABLE 0 parameter \CLK_POLARITY 1 parameter \TRANSPARENT 1 connect \CLK 1'0 connect \EN 1'1 connect \ADDR \mem_r_addr connect \DATA \mem_r_data end would lead to invalid Verilog: reg [1:0] _0_; always @(posedge 1'h0) begin _0_ <= mem_r_addr; end assign mem_r_data = mem[_0_]; Note that there are two potential pitfalls remaining after this change: * For asynchronous ports, the \EN input and \TRANSPARENT parameter are silently ignored. (Per discussion in #760 this is the correct behavior.) * For synchronous transparent ports, the \EN input is ignored. This matches the behavior of the $mem simulation cell. Again, see #760. --- backends/verilog/verilog_backend.cc | 79 +++++++++++++++++++------------------ 1 file changed, 41 insertions(+), 38 deletions(-) (limited to 'backends') diff --git a/backends/verilog/verilog_backend.cc b/backends/verilog/verilog_backend.cc index a7f329ef8..60668f1f0 100644 --- a/backends/verilog/verilog_backend.cc +++ b/backends/verilog/verilog_backend.cc @@ -1065,43 +1065,46 @@ bool dump_cell_expr(std::ostream &f, std::string indent, RTLIL::Cell *cell) use_rd_clk = cell->parameters["\\RD_CLK_ENABLE"].extract(i).as_bool(); rd_clk_posedge = cell->parameters["\\RD_CLK_POLARITY"].extract(i).as_bool(); rd_transparent = cell->parameters["\\RD_TRANSPARENT"].extract(i).as_bool(); + if (use_rd_clk) { - std::ostringstream os; - dump_sigspec(os, sig_rd_clk); - clk_domain_str = stringf("%sedge %s", rd_clk_posedge ? "pos" : "neg", os.str().c_str()); - if( clk_to_lof_body.count(clk_domain_str) == 0 ) - clk_to_lof_body[clk_domain_str] = std::vector(); - } - if (use_rd_clk && !rd_transparent) - { - // for clocked read ports make something like: - // reg [..] temp_id; - // always @(posedge clk) - // if (rd_en) temp_id <= array_reg[r_addr]; - // assign r_data = temp_id; - std::string temp_id = next_auto_id(); - lof_reg_declarations.push_back( stringf("reg [%d:0] %s;\n", sig_rd_data.size() - 1, temp_id.c_str()) ); { std::ostringstream os; - if (sig_rd_en != RTLIL::SigBit(true)) + dump_sigspec(os, sig_rd_clk); + clk_domain_str = stringf("%sedge %s", rd_clk_posedge ? "pos" : "neg", os.str().c_str()); + if( clk_to_lof_body.count(clk_domain_str) == 0 ) + clk_to_lof_body[clk_domain_str] = std::vector(); + } + if (!rd_transparent) + { + // for clocked read ports make something like: + // reg [..] temp_id; + // always @(posedge clk) + // if (rd_en) temp_id <= array_reg[r_addr]; + // assign r_data = temp_id; + std::string temp_id = next_auto_id(); + lof_reg_declarations.push_back( stringf("reg [%d:0] %s;\n", sig_rd_data.size() - 1, temp_id.c_str()) ); + { + std::ostringstream os; + if (sig_rd_en != RTLIL::SigBit(true)) + { + os << stringf("if ("); + dump_sigspec(os, sig_rd_en); + os << stringf(") "); + } + os << stringf("%s <= %s[", temp_id.c_str(), mem_id.c_str()); + dump_sigspec(os, sig_rd_addr); + os << stringf("];\n"); + clk_to_lof_body[clk_domain_str].push_back(os.str()); + } { - os << stringf("if ("); - dump_sigspec(os, sig_rd_en); - os << stringf(") "); + std::ostringstream os; + dump_sigspec(os, sig_rd_data); + std::string line = stringf("assign %s = %s;\n", os.str().c_str(), temp_id.c_str()); + clk_to_lof_body[""].push_back(line); } - os << stringf("%s <= %s[", temp_id.c_str(), mem_id.c_str()); - dump_sigspec(os, sig_rd_addr); - os << stringf("];\n"); - clk_to_lof_body[clk_domain_str].push_back(os.str()); } + else { - std::ostringstream os; - dump_sigspec(os, sig_rd_data); - std::string line = stringf("assign %s = %s;\n", os.str().c_str(), temp_id.c_str()); - clk_to_lof_body[""].push_back(line); - } - } else { - if (rd_transparent) { // for rd-transparent read-ports make something like: // reg [..] temp_id; // always @(posedge clk) @@ -1121,15 +1124,15 @@ bool dump_cell_expr(std::ostream &f, std::string indent, RTLIL::Cell *cell) std::string line = stringf("assign %s = %s[%s];\n", os.str().c_str(), mem_id.c_str(), temp_id.c_str()); clk_to_lof_body[""].push_back(line); } - } else { - // for non-clocked read-ports make something like: - // assign r_data = array_reg[r_addr]; - std::ostringstream os, os2; - dump_sigspec(os, sig_rd_data); - dump_sigspec(os2, sig_rd_addr); - std::string line = stringf("assign %s = %s[%s];\n", os.str().c_str(), mem_id.c_str(), os2.str().c_str()); - clk_to_lof_body[""].push_back(line); } + } else { + // for non-clocked read-ports make something like: + // assign r_data = array_reg[r_addr]; + std::ostringstream os, os2; + dump_sigspec(os, sig_rd_data); + dump_sigspec(os2, sig_rd_addr); + std::string line = stringf("assign %s = %s[%s];\n", os.str().c_str(), mem_id.c_str(), os2.str().c_str()); + clk_to_lof_body[""].push_back(line); } } -- cgit v1.2.3