support -mcpu=baseline, both in stage1 and stage2

See e381a42de9c0f0c5439a926b0ac99026a0373f49 for more details.
This is set up so that if we wish to make "baseline" depend on the
OS in the future, it is possible to do that.

1 files changed, 18 insertions, 14 deletions

diff --git a/lib/std/target.zig b/lib/std/target.zig
index 3d04e3424e..875ccda57f 100644
--- a/lib/std/target.zig
+++ b/lib/std/target.zig
@@ -726,8 +726,7 @@ pub const Target = union(enum) {
         /// Looks like "name+a+b-c-d+e", where "name" is a CPU Model name, "a", "b", and "e"
         /// are examples of CPU features to add to the set, and "c" and "d" are examples of CPU features
         /// to remove from the set.
-        /// The default value of `null` means to use the "baseline" feature set.
-        cpu: ?[]const u8 = null,
+        cpu_features: []const u8 = "baseline",
     };
 
     pub fn parse(args: ParseOptions) !Target {
@@ -742,23 +741,29 @@ pub const Target = union(enum) {
         const abi = if (abi_name) |n| try Abi.parse(n) else Abi.default(arch, os);
 
         const all_features = arch.allFeaturesList();
-        const cpu: Cpu = if (args.cpu) |cpu_text| blk: {
-            var index: usize = 0;
-            while (index < cpu_text.len and cpu_text[index] != '+' and cpu_text[index] != '-') {
-                index += 1;
-            }
-            const cpu_name = cpu_text[0..index];
+        var index: usize = 0;
+        while (index < args.cpu_features.len and
+            args.cpu_features[index] != '+' and
+            args.cpu_features[index] != '-')
+        {
+            index += 1;
+        }
+        const cpu_name = args.cpu_features[0..index];
+        const cpu: Cpu = if (mem.eql(u8, cpu_name, "baseline")) Cpu.baseline(arch) else blk: {
             const cpu_model = try arch.parseCpuModel(cpu_name);
 
             var set = cpu_model.features;
-            while (index < cpu_text.len) {
-                const op = cpu_text[index];
+            while (index < args.cpu_features.len) {
+                const op = args.cpu_features[index];
                 index += 1;
                 const start = index;
-                while (index < cpu_text.len and cpu_text[index] != '+' and cpu_text[index] != '-') {
+                while (index < args.cpu_features.len and
+                    args.cpu_features[index] != '+' and
+                    args.cpu_features[index] != '-')
+                {
                     index += 1;
                 }
-                const feature_name = cpu_text[start..index];
+                const feature_name = args.cpu_features[start..index];
                 for (all_features) |feature, feat_index_usize| {
                     const feat_index = @intCast(Cpu.Feature.Set.Index, feat_index_usize);
                     if (mem.eql(u8, feature_name, feature.name)) {
@@ -779,8 +784,7 @@ pub const Target = union(enum) {
                 .model = cpu_model,
                 .features = set,
             };
-        } else Cpu.baseline(arch);
-
+        };
         var cross = Cross{
             .cpu = cpu,
             .os = os,