From dafe1a910d1b236e7cfba40231f3c730f18f5d1f Mon Sep 17 00:00:00 2001
From: Shawn Gao <16461362+gaosui@users.noreply.github.com>
Date: Mon, 23 Sep 2024 15:08:58 -0700
Subject: [PATCH] Append disabled LLVM CPU features after enabled ones

---
 src/Package/Module.zig | 27 +++++++++++++++++++--------
 1 file changed, 19 insertions(+), 8 deletions(-)

diff --git a/src/Package/Module.zig b/src/Package/Module.zig
index 0e777145d9..996e58ddfb 100644
--- a/src/Package/Module.zig
+++ b/src/Package/Module.zig
@@ -312,18 +312,29 @@ pub fn create(arena: Allocator, options: CreateOptions) !*Package.Module {
         if (!options.global.use_llvm) break :b null;
 
         var buf = std.ArrayList(u8).init(arena);
-        for (target.cpu.arch.allFeaturesList(), 0..) |feature, index_usize| {
-            const index = @as(std.Target.Cpu.Feature.Set.Index, @intCast(index_usize));
-            const is_enabled = target.cpu.features.isEnabled(index);
+        var disabled_features = std.ArrayList(u8).init(arena);
+        defer disabled_features.deinit();
 
+        // Append disabled features after enabled ones, so that their effects aren't overwritten.
+        for (target.cpu.arch.allFeaturesList()) |feature| {
             if (feature.llvm_name) |llvm_name| {
-                const plus_or_minus = "-+"[@intFromBool(is_enabled)];
-                try buf.ensureUnusedCapacity(2 + llvm_name.len);
-                buf.appendAssumeCapacity(plus_or_minus);
-                buf.appendSliceAssumeCapacity(llvm_name);
-                buf.appendSliceAssumeCapacity(",");
+                const is_enabled = target.cpu.features.isEnabled(feature.index);
+
+                if (is_enabled) {
+                    try buf.ensureUnusedCapacity(2 + llvm_name.len);
+                    buf.appendAssumeCapacity('+');
+                    buf.appendSliceAssumeCapacity(llvm_name);
+                    buf.appendAssumeCapacity(',');
+                } else {
+                    try disabled_features.ensureUnusedCapacity(2 + llvm_name.len);
+                    disabled_features.appendAssumeCapacity('-');
+                    disabled_features.appendSliceAssumeCapacity(llvm_name);
+                    disabled_features.appendAssumeCapacity(',');
+                }
             }
         }
+
+        try buf.appendSlice(disabled_features.items);
         if (buf.items.len == 0) break :b "";
         assert(std.mem.endsWith(u8, buf.items, ","));
         buf.items[buf.items.len - 1] = 0;