Fix #embed support in bbasm and use it when available.

This removes the atomic rename for bbasm outputs because it embeds
the resulting paths into the `.cc` files in embed mode. In any case
the write should be fast enough to not be a big risk for interrupted
builds.

This was tested with Clang 19 only (gcc hasn't had a release that
supports `#embed` yet).

CMakeLists.txt

@@ -4,6 +4,7 @@ project(nextpnr CXX)
 set(CMAKE_MODULE_PATH "${CMAKE_SOURCE_DIR}/cmake" ${CMAKE_MODULE_PATH})
 
 include(CheckCXXCompilerFlag)
+include(CheckCXXCompilerHashEmbed)
 
 if (NOT DEFINED CMAKE_SUPPRESS_DEVELOPER_WARNINGS)
     set(CMAKE_SUPPRESS_DEVELOPER_WARNINGS 1 CACHE INTERNAL "No dev warnings")
@@ -55,7 +56,11 @@ else()
     set(CMAKE_INTERPROCEDURAL_OPTIMIZATION FALSE)
 endif()
 
-if (WIN32)
+check_cxx_compiler_hash_embed(HAS_HASH_EMBED CXX_FLAGS_HASH_EMBED)
+set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${CXX_FLAGS_HASH_EMBED}")
+if (HAS_HASH_EMBED)
+    set(BBASM_MODE "embed")
+elseif (WIN32)
     set(BBASM_MODE "resource")
 elseif (EXTERNAL_CHIPDB)
     set(BBASM_MODE "binary")

bba/CMakeLists.txt

@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.5)
+cmake_minimum_required(VERSION 3.25)
 project(bba CXX)
 
 find_package(Boost REQUIRED COMPONENTS

bba/main.cc

@@ -443,20 +443,20 @@ int main(int argc, char **argv)
         for (auto &s : postText)
             fprintf(fileOut, "%s\n", s.c_str());
     } else if (writeE) {
-        for (auto &s : preText)
-            fprintf(fileOut, "%s\n", s.c_str());
-
-        fprintf(fileOut, "const char %s[%d] =\n", streams[0].name.c_str(), int(data.size()) + 1);
-        fprintf(fileOut, "#embed_str \"%s\"\n", boost::filesystem::path(files.at(2)).stem().c_str());
-        fprintf(fileOut, ";\n");
-
-        for (auto &s : postText)
-            fprintf(fileOut, "%s\n", s.c_str());
-
         FILE *fileBin = fopen(files.at(2).c_str(), "wb");
         assert(fileBin != nullptr);
         fwrite(data.data(), int(data.size()), 1, fileBin);
         fclose(fileBin);
+
+        for (auto &s : preText)
+            fprintf(fileOut, "%s\n", s.c_str());
+
+        fprintf(fileOut, "const char %s[%d] = {\n", streams[0].name.c_str(), int(data.size()) + 1);
+        fprintf(fileOut, "#embed \"%s\"\n", boost::filesystem::path(files.at(2)).c_str());
+        fprintf(fileOut, "};\n");
+
+        for (auto &s : postText)
+            fprintf(fileOut, "%s\n", s.c_str());
     } else {
         fwrite(data.data(), int(data.size()), 1, fileOut);
     }

cmake/BBAsm.cmake

@@ -81,11 +81,7 @@ function(add_bba_compile_command)
             COMMAND
                 bbasm ${BBASM_ENDIAN_FLAG}
                 ${arg_INPUT}
-                ${arg_OUTPUT}.new
+                ${arg_OUTPUT}
-            COMMAND
-                ${CMAKE_COMMAND} -E rename # atomic update
-                    ${arg_OUTPUT}.new
-                    ${arg_OUTPUT}
             DEPENDS
                 bbasm
                 ${arg_INPUT}
@@ -120,16 +116,8 @@ function(add_bba_compile_command)
             COMMAND
                 bbasm ${BBASM_ENDIAN_FLAG} --e
                 ${arg_INPUT}
-                ${arg_OUTPUT}.cc.new
+                ${arg_OUTPUT}.cc
-                ${arg_OUTPUT}.new
+                ${arg_OUTPUT}
-            COMMAND
-                ${CMAKE_COMMAND} -E rename # atomic update
-                    ${arg_OUTPUT}.cc.new
-                    ${arg_OUTPUT}.cc
-            COMMAND
-                ${CMAKE_COMMAND} -E rename # atomic update
-                    ${arg_OUTPUT}.new
-                    ${arg_OUTPUT}
             DEPENDS
                 bbasm
                 ${arg_INPUT}
@@ -149,17 +137,20 @@ function(add_bba_compile_command)
             COMMAND
                 bbasm ${BBASM_ENDIAN_FLAG} --c
                 ${arg_INPUT}
-                ${arg_OUTPUT}.cc.new
+                ${arg_OUTPUT}.cc
-            COMMAND
-                ${CMAKE_COMMAND} -E rename # atomic update
-                    ${arg_OUTPUT}.cc.new
-                    ${arg_OUTPUT}.cc
             DEPENDS
                 bbasm
                 ${arg_INPUT}
             VERBATIM
         )
 
+        if (NOT MSVC)
+            set_source_files_properties(
+                ${arg_OUTPUT}.cc PROPERTIES
+                COMPILE_OPTIONS "-w;-g0;-O0"
+            )
+        endif()
+
         target_sources(
             ${arg_TARGET} PRIVATE
             ${arg_OUTPUT}.cc

cmake/CheckCXXCompilerHashEmbed.cmake

@@ -0,0 +1,30 @@
+# This is checking for CMAKE_CXX_COMPILER's ability to use `#embed`.
+# BBAsm is using `#embed` (C) and not `std::embed` (C++) even though it emits C++ code.
+# As of 2025-01-16: Note that the usage of `#embed` in C has different rules (the C++ one is
+# an extension, the C one is in the C23 standard).
+
+# Example usage:
+#
+# check_cxx_compiler_hash_embed(HAS_HASH_EMBED CXX_FLAGS_HASH_EMBED)
+# set(CMAKE_CXX_FLAGS ${CXX_FLAGS_HASH_EMBED} ${CMAKE_CXX_FLAGS})
+#
+function(check_cxx_compiler_hash_embed VAR FLAGS_VAR)
+    try_compile(
+        ${VAR}
+        SOURCE_FROM_CONTENT
+            compiletest.cc
+            "const char s[] = {\n#embed \"${CMAKE_CURRENT_FUNCTION_LIST_FILE}\"\n};\nint main() {}"
+    )
+    if (${VAR})
+        if (FLAGS_VAR)
+            check_cxx_compiler_flag(-Wc23-extensions HAS_Wc23-extensions)
+            if (HAS_Wc23-extensions)
+                set(${FLAGS_VAR} -Wno-c23-extensions PARENT_SCOPE)
+            endif()
+        endif()
+
+        message(STATUS "C++ compiler supports #embed")
+    else()
+        message(STATUS "C++ compiler does NOT support #embed")
+    endif()
+endfunction()

ecp5/CMakeLists.txt

@@ -1,7 +1,6 @@
 include(FindTrellis)
 
 add_library(chipdb-${family} OBJECT)
-target_compile_options(chipdb-${family} PRIVATE -w -g0 -O0)
 target_compile_definitions(chipdb-${family} PRIVATE NEXTPNR_NAMESPACE=nextpnr_${family})
 target_include_directories(chipdb-${family} PRIVATE .)
 

gowin/CMakeLists.txt

@@ -1,7 +1,6 @@
 include(FindApycula)
 
 add_library(chipdb-${family} OBJECT)
-target_compile_options(chipdb-${family} PRIVATE -w -g0 -O0)
 target_compile_definitions(chipdb-${family} PRIVATE NEXTPNR_NAMESPACE=nextpnr_${family})
 target_include_directories(chipdb-${family} PRIVATE .)
 

ice40/CMakeLists.txt

@@ -1,7 +1,6 @@
 include(FindIceStorm)
 
 add_library(chipdb-${family} OBJECT)
-target_compile_options(chipdb-${family} PRIVATE -w -g0 -O0)
 target_compile_definitions(chipdb-${family} PRIVATE NEXTPNR_NAMESPACE=nextpnr_${family})
 target_include_directories(chipdb-${family} PRIVATE .)
 

machxo2/CMakeLists.txt

@@ -1,7 +1,6 @@
 include(FindTrellis)
 
 add_library(chipdb-${family} OBJECT)
-target_compile_options(chipdb-${family} PRIVATE -w -g0 -O0)
 target_compile_definitions(chipdb-${family} PRIVATE NEXTPNR_NAMESPACE=nextpnr_${family})
 target_include_directories(chipdb-${family} PRIVATE .)
 

nexus/CMakeLists.txt

@@ -7,7 +7,6 @@ set(NEXUS_FAMILIES ${ALL_NEXUS_FAMILIES} CACHE STRING
 message(STATUS "Enabled Nexus families: ${NEXUS_FAMILIES}")
 
 add_library(chipdb-${family} OBJECT)
-target_compile_options(chipdb-${family} PRIVATE -w -g0 -O0)
 target_compile_definitions(chipdb-${family} PRIVATE NEXTPNR_NAMESPACE=nextpnr_${family})
 target_include_directories(chipdb-${family} PRIVATE .)