Add command line options and build system support for specifying LLVM target cpu and features

src/all_types.hpp

@@ -1894,6 +1894,9 @@ struct CodeGen {
 
     const char **clang_argv;
     size_t clang_argv_len;
+
+    const char *llvm_cpu;
+    const char *llvm_features;
 };
 
 struct ZigVar {

src/codegen.cpp

@@ -8113,20 +8113,39 @@ static void init(CodeGen *g) {
 
     const char *target_specific_cpu_args;
     const char *target_specific_features;
-    if (g->zig_target->is_native) {
-        // LLVM creates invalid binaries on Windows sometimes.
-        // See https://github.com/ziglang/zig/issues/508
-        // As a workaround we do not use target native features on Windows.
-        if (g->zig_target->os == OsWindows || g->zig_target->os == OsUefi) {
-            target_specific_cpu_args = "";
-            target_specific_features = "";
+    // If the user has overridden one of either cpu or features,
+    // use that in place of empty string or native.
+    if (g->llvm_cpu != nullptr) {
+        target_specific_cpu_args = g->llvm_cpu;
+    } else {
+        if (g->zig_target->is_native) {
+            // LLVM creates invalid binaries on Windows sometimes.
+            // See https://github.com/ziglang/zig/issues/508
+            // As a workaround we do not use target native features on Windows.
+            if (g->zig_target->os == OsWindows || g->zig_target->os == OsUefi) {
+                target_specific_cpu_args = "";
+            } else {
+                target_specific_cpu_args = ZigLLVMGetHostCPUName();
+            }
         } else {
-            target_specific_cpu_args = ZigLLVMGetHostCPUName();
-            target_specific_features = ZigLLVMGetNativeFeatures();
+            target_specific_cpu_args = "";
         }
+    }
+    if (g->llvm_features != nullptr) {
+        target_specific_features = g->llvm_features;
     } else {
-        target_specific_cpu_args = "";
-        target_specific_features = "";
+        if (g->zig_target->is_native) {
+            // LLVM creates invalid binaries on Windows sometimes.
+            // See https://github.com/ziglang/zig/issues/508
+            // As a workaround we do not use target native features on Windows.
+            if (g->zig_target->os == OsWindows || g->zig_target->os == OsUefi) {
+                target_specific_features = "";
+            } else {
+                target_specific_features = ZigLLVMGetNativeFeatures();
+            }
+        } else {
+            target_specific_features = "";
+        }
     }
 
     g->target_machine = LLVMCreateTargetMachine(target_ref, buf_ptr(&g->triple_str),

src/link.cpp

@@ -34,6 +34,8 @@ static CodeGen *create_child_codegen(CodeGen *parent_gen, Buf *root_src_path, Ou
     child_gen->verbose_cimport = parent_gen->verbose_cimport;
     child_gen->verbose_cc = parent_gen->verbose_cc;
     child_gen->llvm_argv = parent_gen->llvm_argv;
+    child_gen->llvm_cpu = parent_gen->llvm_cpu;
+    child_gen->llvm_features = parent_gen->llvm_features;
     child_gen->dynamic_linker_path = parent_gen->dynamic_linker_path;
 
     codegen_set_strip(child_gen, parent_gen->strip_debug_symbols);

src/main.cpp

@@ -84,6 +84,8 @@ static int print_full_usage(const char *arg0, FILE *file, int return_code) {
         "  -dirafter [dir]              same as -isystem but do it last\n"
         "  -isystem [dir]               add additional search path for other .h files\n"
         "  -mllvm [arg]                 forward an arg to LLVM's option processing\n"
+        "  --llvm-cpu [cpu]             set the LLVM cpu option (-mcpu)\n"
+        "  --llvm-features [features]   set the LLVM cpu features option (-mattr)\n"
         "  --override-std-dir [arg]     use an alternate Zig standard library\n"
         "\n"
         "Link Options:\n"
@@ -450,6 +452,8 @@ int main(int argc, char **argv) {
     ValgrindSupport valgrind_support = ValgrindSupportAuto;
     WantPIC want_pic = WantPICAuto;
     WantStackCheck want_stack_check = WantStackCheckAuto;
+    const char *llvm_cpu = nullptr;
+    const char *llvm_features = nullptr;
 
     ZigList<const char *> llvm_argv = {0};
     llvm_argv.append("zig (LLVM option parsing)");
@@ -745,6 +749,10 @@ int main(int argc, char **argv) {
                     clang_argv.append(argv[i]);
 
                     llvm_argv.append(argv[i]);
+                } else if (strcmp(arg, "--llvm-cpu") == 0) {
+                    llvm_cpu = argv[i];
+                } else if (strcmp(arg, "--llvm-features") == 0) {
+                    llvm_features = argv[i];
                 } else if (strcmp(arg, "--override-std-dir") == 0) {
                     override_std_dir = buf_create_from_str(argv[i]);
                 } else if (strcmp(arg, "--override-lib-dir") == 0) {
@@ -1055,9 +1063,11 @@ int main(int argc, char **argv) {
             } else {
                 cache_dir_buf = buf_create_from_str(cache_dir);
             }
-            CodeGen *g = codegen_create(main_pkg_path, zig_root_source_file, &target, out_type, build_mode,
-                    override_lib_dir, override_std_dir, libc, cache_dir_buf);
+            CodeGen *g = codegen_create(main_pkg_path, zig_root_source_file, &target, 
+                    out_type, build_mode, override_lib_dir, override_std_dir, libc, cache_dir_buf);
             if (llvm_argv.length >= 2) codegen_set_llvm_argv(g, llvm_argv.items + 1, llvm_argv.length - 2);
+            g->llvm_cpu = llvm_cpu;
+            g->llvm_features = llvm_features;
             g->valgrind_support = valgrind_support;
             g->want_pic = want_pic;
             g->want_stack_check = want_stack_check;

std/build.zig

@@ -965,6 +965,8 @@ pub const LibExeObjStep = struct {
     name_prefix: []const u8,
     filter: ?[]const u8,
     single_threaded: bool,
+    llvm_cpu: ?[]const u8,
+    llvm_features: ?[]const u8,
 
     root_src: ?[]const u8,
     out_h_filename: []const u8,
@@ -1071,6 +1073,8 @@ pub const LibExeObjStep = struct {
             .output_dir = null,
             .need_system_paths = false,
             .single_threaded = false,
+            .llvm_cpu = null,
+            .llvm_features = null,
         };
         self.computeOutFileNames();
         return self;
@@ -1241,6 +1245,14 @@ pub const LibExeObjStep = struct {
         self.disable_gen_h = value;
     }
 
+    pub fn setLlvmCpu(self: *LibExeObjStep, cpu: []const u8) void {
+        self.llvm_cpu = cpu;
+    }
+
+    pub fn setLlvmFeatures(self: *LibExeObjStep, features: []const u8) void {
+        self.llvm_features = features;
+    }
+
     /// Unless setOutputDir was called, this function must be called only in
     /// the make step, from a step that has declared a dependency on this one.
     /// To run an executable built with zig build, use `run`, or create an install step and invoke it.
@@ -1445,6 +1457,16 @@ pub const LibExeObjStep = struct {
             try zig_args.append("--single-threaded");
         }
 
+        if (self.llvm_cpu) |llvm_cpu| {
+            try zig_args.append("--llvm-cpu");
+            try zig_args.append(llvm_cpu);
+        }
+
+        if (self.llvm_features) |llvm_features| {
+            try zig_args.append("--llvm-features");
+            try zig_args.append(llvm_features);
+        }
+
         switch (self.build_mode) {
             builtin.Mode.Debug => {},
             builtin.Mode.ReleaseSafe => zig_args.append("--release-safe") catch unreachable,