Add WASI platform support.

This includes the following significant changes:
  * Patching ezsat and minisat to disable resource limiting code
    on WASM/WASI, since the POSIX functions they use are unavailable.
  * Adding a new definition, YOSYS_DISABLE_SPAWN, present if platform
    does not support spawning subprocesses (i.e. Emscripten or WASI).
    This definition hides the definition of `run_command()`.
  * Adding a new Makefile flag, DISABLE_SPAWN, present in the same
    condition. This flag disables all passes that require spawning
    subprocesses for their function.

passes/cmds/Makefile.inc

@@ -1,5 +1,7 @@
 
+ifeq ($(DISABLE_SPAWN),0)
 OBJS += passes/cmds/exec.o
+endif
 OBJS += passes/cmds/add.o
 OBJS += passes/cmds/delete.o
 OBJS += passes/cmds/design.o
@@ -32,6 +34,8 @@ OBJS += passes/cmds/chformal.o
 OBJS += passes/cmds/chtype.o
 OBJS += passes/cmds/blackbox.o
 OBJS += passes/cmds/ltp.o
+ifeq ($(DISABLE_SPAWN),0)
 OBJS += passes/cmds/bugpoint.o
+endif
 OBJS += passes/cmds/scratchpad.o
 OBJS += passes/cmds/logger.o

passes/cmds/cover.cc

@@ -101,8 +101,8 @@ struct CoverPass : public Pass {
 				const std::string &filename = args[++argidx];
 				FILE *f = nullptr;
 				if (args[argidx-1] == "-d") {
-			#ifdef _WIN32
-					log_cmd_error("The 'cover -d' option is not supported on win32.\n");
+			#if defined(_WIN32) || defined(__wasm)
+					log_cmd_error("The 'cover -d' option is not supported on this platform.\n");
 			#else
 					char filename_buffer[4096];
 					snprintf(filename_buffer, 4096, "%s/yosys_cover_%d_XXXXXX.txt", filename.c_str(), getpid());

passes/cmds/show.cc

@@ -682,7 +682,7 @@ struct ShowPass : public Pass {
 		std::vector<std::pair<std::string, RTLIL::Selection>> color_selections;
 		std::vector<std::pair<std::string, RTLIL::Selection>> label_selections;
 
-#if defined(EMSCRIPTEN) || defined(_WIN32)
+#if defined(_WIN32) || defined(YOSYS_DISABLE_SPAWN)
 		std::string format = "dot";
 		std::string prefix = "show";
 #else
@@ -849,10 +849,15 @@ struct ShowPass : public Pass {
 			std::string cmd = stringf(DOT_CMD, format.c_str(), dot_file.c_str(), out_file.c_str(), out_file.c_str(), out_file.c_str());
 			#undef DOT_CMD
 			log("Exec: %s\n", cmd.c_str());
-			if (run_command(cmd) != 0)
-				log_cmd_error("Shell command failed!\n");
+			#if !defined(YOSYS_DISABLE_SPAWN)
+				if (run_command(cmd) != 0)
+					log_cmd_error("Shell command failed!\n");
+			#endif
 		}
 
+		#if defined(YOSYS_DISABLE_SPAWN)
+			log_assert(viewer_exe.empty() && !format.empty());
+		#else
 		if (!viewer_exe.empty()) {
 			#ifdef _WIN32
 				// system()/cmd.exe does not understand single quotes nor
@@ -876,6 +881,7 @@ struct ShowPass : public Pass {
 			if (run_command(cmd) != 0)
 				log_cmd_error("Shell command failed!\n");
 		}
+		#endif
 
 		if (flag_pause) {
 		#ifdef YOSYS_ENABLE_READLINE

passes/sat/Makefile.inc

@@ -13,5 +13,6 @@ OBJS += passes/sat/fmcombine.o
 OBJS += passes/sat/mutate.o
 OBJS += passes/sat/cutpoint.o
 OBJS += passes/sat/fminit.o
+ifeq ($(DISABLE_SPAWN),0)
 OBJS += passes/sat/qbfsat.o
-
+endif

passes/techmap/Makefile.inc

@@ -57,7 +57,7 @@ passes/techmap/techmap.inc: techlibs/common/techmap.v
 
 passes/techmap/techmap.o: passes/techmap/techmap.inc
 
-ifneq ($(CONFIG),emcc)
+ifeq ($(DISABLE_SPAWN),0)
 TARGETS += $(PROGRAM_PREFIX)yosys-filterlib$(EXE)
 EXTRA_OBJS += passes/techmap/filterlib.o
 

passes/techmap/abc.cc

@@ -771,7 +771,10 @@ void abc_module(RTLIL::Design *design, RTLIL::Module *current_module, std::strin
 		if (abc_script[i] == ';' && abc_script[i+1] == ' ')
 			abc_script[i+1] = '\n';
 
-	FILE *f = fopen(stringf("%s/abc.script", tempdir_name.c_str()).c_str(), "wt");
+	std::string buffer = stringf("%s/abc.script", tempdir_name.c_str());
+	FILE *f = fopen(buffer.c_str(), "wt");
+	if (f == nullptr)
+		log_error("Opening %s for writing failed: %s\n", buffer.c_str(), strerror(errno));
 	fprintf(f, "%s\n", abc_script.c_str());
 	fclose(f);
 
@@ -807,7 +810,7 @@ void abc_module(RTLIL::Design *design, RTLIL::Module *current_module, std::strin
 
 	handle_loops();
 
-	std::string buffer = stringf("%s/input.blif", tempdir_name.c_str());
+	buffer = stringf("%s/input.blif", tempdir_name.c_str());
 	f = fopen(buffer.c_str(), "wt");
 	if (f == nullptr)
 		log_error("Opening %s for writing failed: %s\n", buffer.c_str(), strerror(errno));
@@ -1541,11 +1544,15 @@ struct AbcPass : public Pass {
 
 		size_t argidx, g_argidx;
 		bool g_arg_from_cmd = false;
+#if defined(__wasm)
+		const char *pwd = ".";
+#else
 		char pwd [PATH_MAX];
 		if (!getcwd(pwd, sizeof(pwd))) {
 			log_cmd_error("getcwd failed: %s\n", strerror(errno));
 			log_abort();
 		}
+#endif
 		for (argidx = 1; argidx < args.size(); argidx++) {
 			std::string arg = args[argidx];
 			if (arg == "-exe" && argidx+1 < args.size()) {

passes/techmap/abc9_exe.cc

@@ -420,11 +420,15 @@ struct Abc9ExePass : public Pass {
 		}
 
 		size_t argidx;
+#if defined(__wasm)
+		const char *pwd = ".";
+#else
 		char pwd [PATH_MAX];
 		if (!getcwd(pwd, sizeof(pwd))) {
 			log_cmd_error("getcwd failed: %s\n", strerror(errno));
 			log_abort();
 		}
+#endif
 		for (argidx = 1; argidx < args.size(); argidx++) {
 			std::string arg = args[argidx];
 			if (arg == "-exe" && argidx+1 < args.size()) {