From: whitequark <whitequark@whitequark.org>
Date: Mon, 21 Dec 2020 00:22:50 +0000 (+0000)
Subject: cxxrtl: speed up commits on clang.
X-Git-Tag: working-ls180~159^2~1
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=40ca9d038b1e657b9b9ac17e7e5a2969c9922e00;p=yosys.git

cxxrtl: speed up commits on clang.

On Minerva SoC SRAM compiled with clang-11, this change cuts commit
time in half (!) and overall time by 20%. When compiled with gcc-10,
there is no difference.
---

diff --git a/backends/cxxrtl/cxxrtl_backend.cc b/backends/cxxrtl/cxxrtl_backend.cc
index 9875aba60..3b2fb4985 100644
--- a/backends/cxxrtl/cxxrtl_backend.cc
+++ b/backends/cxxrtl/cxxrtl_backend.cc
@@ -1702,19 +1702,19 @@ struct CxxrtlWorker {
 					continue;
 				}
 				if (!module->get_bool_attribute(ID(cxxrtl_blackbox)) || wire->port_id != 0)
-					f << indent << "changed |= " << mangle(wire) << ".commit();\n";
+					f << indent << "if (" << mangle(wire) << ".commit()) changed = true;\n";
 			}
 			if (!module->get_bool_attribute(ID(cxxrtl_blackbox))) {
 				for (auto memory : module->memories) {
 					if (!writable_memories[memory.second])
 						continue;
-					f << indent << "changed |= " << mangle(memory.second) << ".commit();\n";
+					f << indent << "if (" << mangle(memory.second) << ".commit()) changed = true;\n";
 				}
 				for (auto cell : module->cells()) {
 					if (is_internal_cell(cell->type))
 						continue;
 					const char *access = is_cxxrtl_blackbox_cell(cell) ? "->" : ".";
-					f << indent << "changed |= " << mangle(cell) << access << "commit();\n";
+					f << indent << "if (" << mangle(cell) << access << "commit()) changed = true;\n";
 				}
 			}
 			f << indent << "return changed;\n";