improvements to riscv support

src/codegen.cpp

@@ -8390,13 +8390,13 @@ void add_cc_args(CodeGen *g, ZigList<const char *> &args, const char *out_dep_pa
         }
     }
 
+    // According to Rich Felker libc headers are supposed to go before C language headers.
     for (size_t i = 0; i < g->libc_include_dir_len; i += 1) {
         Buf *include_dir = g->libc_include_dir_list[i];
         args.append("-isystem");
         args.append(buf_ptr(include_dir));
     }
 
-    // According to Rich Felker libc headers are supposed to go before C language headers.
     args.append("-isystem");
     args.append(buf_ptr(g->zig_c_headers_dir));
 
@@ -8405,6 +8405,21 @@ void add_cc_args(CodeGen *g, ZigList<const char *> &args, const char *out_dep_pa
     } else {
         args.append("-target");
         args.append(buf_ptr(&g->llvm_triple_str));
+
+        if (target_is_musl(g->zig_target) && target_is_riscv(g->zig_target)) {
+            // Musl depends on atomic instructions, which are disabled by default in Clang/LLVM's
+            // cross compilation CPU info for RISCV.
+            switch (g->zig_target->arch) {
+                case ZigLLVM_riscv32:
+                    args.append("-march=rv32ia");
+                    break;
+                case ZigLLVM_riscv64:
+                    args.append("-march=rv64ia");
+                    break;
+                default:
+                    zig_unreachable();
+            }
+        }
     }
     if (g->zig_target->os == OsFreestanding) {
         args.append("-ffreestanding");
@@ -8474,6 +8489,7 @@ void add_cc_args(CodeGen *g, ZigList<const char *> &args, const char *out_dep_pa
     for (size_t arg_i = 0; arg_i < g->clang_argv_len; arg_i += 1) {
         args.append(g->clang_argv[arg_i]);
     }
+
 }
 
 void codegen_translate_c(CodeGen *g, Buf *full_path, FILE *out_file, bool use_userland_implementation) {

src/link.cpp

@@ -1658,7 +1658,9 @@ static void construct_linker_job_elf(LinkJob *lj) {
             crt1o = "Scrt1.o";
         }
         lj->args.append(get_libc_crt_file(g, crt1o));
-        lj->args.append(get_libc_crt_file(g, "crti.o"));
+        if (target_libc_needs_crti_crtn(g->zig_target)) {
+            lj->args.append(get_libc_crt_file(g, "crti.o"));
+        }
     }
 
     for (size_t i = 0; i < g->rpath_list.length; i += 1) {
@@ -1791,7 +1793,7 @@ static void construct_linker_job_elf(LinkJob *lj) {
     }
 
     // crt end
-    if (lj->link_in_crt) {
+    if (lj->link_in_crt && target_libc_needs_crti_crtn(g->zig_target)) {
         lj->args.append(get_libc_crt_file(g, "crtn.o"));
     }
 

src/target.cpp

@@ -1739,8 +1739,25 @@ const char *target_arch_musl_name(ZigLLVM_ArchType arch) {
 }
 
 bool target_supports_libunwind(const ZigTarget *target) {
-    if (target->arch == ZigLLVM_arm || target->arch == ZigLLVM_armeb) {
+    switch (target->arch) {
+        case ZigLLVM_arm:
+        case ZigLLVM_armeb:
+        case ZigLLVM_riscv32:
+        case ZigLLVM_riscv64:
+            return false;
+        default:
+            return true;
+    }
+    return true;
+}
+
+bool target_libc_needs_crti_crtn(const ZigTarget *target) {
+    if (target->arch == ZigLLVM_riscv32 || target->arch == ZigLLVM_riscv64) {
         return false;
     }
     return true;
 }
+
+bool target_is_riscv(const ZigTarget *target) {
+    return target->arch == ZigLLVM_riscv32 || target->arch == ZigLLVM_riscv64;
+}

src/target.hpp

@@ -186,6 +186,7 @@ bool target_abi_is_musl(ZigLLVM_EnvironmentType abi);
 bool target_is_glibc(const ZigTarget *target);
 bool target_is_musl(const ZigTarget *target);
 bool target_is_wasm(const ZigTarget *target);
+bool target_is_riscv(const ZigTarget *target);
 bool target_is_android(const ZigTarget *target);
 bool target_is_single_threaded(const ZigTarget *target);
 bool target_supports_stack_probing(const ZigTarget *target);
@@ -197,5 +198,6 @@ uint32_t target_arch_pointer_bit_width(ZigLLVM_ArchType arch);
 
 size_t target_libc_count(void);
 void target_libc_enum(size_t index, ZigTarget *out_target);
+bool target_libc_needs_crti_crtn(const ZigTarget *target);
 
 #endif