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author | whitequark <whitequark@whitequark.org> | 2019-01-29 02:24:00 +0000 |
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committer | whitequark <whitequark@whitequark.org> | 2019-01-29 02:24:00 +0000 |
commit | da65e1e8d9552f64e1e03c08108ca0532719bbfe (patch) | |
tree | bfdf72ced308dd77096bc29d4445f640dc50bc33 /backends/verilog/verilog_backend.cc | |
parent | 266511b29eb66486bd17210eb28454a2efee218a (diff) | |
download | yosys-da65e1e8d9552f64e1e03c08108ca0532719bbfe.tar.gz yosys-da65e1e8d9552f64e1e03c08108ca0532719bbfe.tar.bz2 yosys-da65e1e8d9552f64e1e03c08108ca0532719bbfe.zip |
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.
Diffstat (limited to 'backends/verilog/verilog_backend.cc')
-rw-r--r-- | backends/verilog/verilog_backend.cc | 79 |
1 files changed, 41 insertions, 38 deletions
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<std::string>(); - } - 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<std::string>(); + } + 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); } } |