Merge pull request #22526 from alexrp/cpu-feature-hacks

`std.zig.system`: Move CPU feature hacks after ABI detection.

Author: andrewrk

lib/compiler_rt/memcpy.zig

@@ -9,36 +9,12 @@ comptime {
     }
 }
 
-const llvm_cannot_lower = switch (builtin.cpu.arch) {
-    .arm, .armeb, .thumb, .thumbeb => builtin.zig_backend == .stage2_llvm,
-    else => false,
-};
-
 fn memcpy(noalias opt_dest: ?[*]u8, noalias opt_src: ?[*]const u8, len: usize) callconv(.C) ?[*]u8 {
-    if (llvm_cannot_lower) {
-        for (0..len) |i| opt_dest.?[i] = opt_src.?[i];
-        return opt_dest;
-    } else {
-        return memmove(opt_dest, opt_src, len);
-    }
+    return memmove(opt_dest, opt_src, len);
 }
 
-/// A port of https://github.com/facebook/folly/blob/1c8bc50e88804e2a7361a57cd9b551dd10f6c5fd/folly/memcpy.S
 fn memmove(opt_dest: ?[*]u8, opt_src: ?[*]const u8, len: usize) callconv(.C) ?[*]u8 {
-    if (llvm_cannot_lower) {
-        if (@intFromPtr(opt_dest) < @intFromPtr(opt_src)) {
-            for (0..len) |i| opt_dest.?[i] = opt_src.?[i];
-            return opt_dest;
-        } else {
-            var index = len;
-            while (index != 0) {
-                index -= 1;
-                opt_dest.?[index] = opt_src.?[index];
-            }
-            return opt_dest;
-        }
-    }
-
+    // a port of https://github.com/facebook/folly/blob/1c8bc50e88804e2a7361a57cd9b551dd10f6c5fd/folly/memcpy.S
     if (len == 0) {
         @branchHint(.unlikely);
         return opt_dest;

lib/std/zig/system.zig

@@ -399,22 +399,26 @@ pub fn resolveTargetQuery(query: Target.Query) DetectError!Target {
         query.cpu_features_sub,
     );
 
-    if (cpu.arch == .hexagon) {
-        // Both LLVM and LLD have broken support for the small data area. Yet LLVM has the feature
-        // on by default for all Hexagon CPUs. Clang sort of solves this by defaulting the `-gpsize`
-        // command line parameter for the Hexagon backend to 0, so that no constants get placed in
-        // the SDA. (This of course breaks down if the user passes `-G <n>` to Clang...) We can't do
-        // the `-gpsize` hack because we can have multiple concurrent LLVM emit jobs, and command
-        // line options in LLVM are shared globally. So just force this feature off. Lovely stuff.
-        cpu.features.removeFeature(@intFromEnum(Target.hexagon.Feature.small_data));
-    }
+    var result = try detectAbiAndDynamicLinker(cpu, os, query);
 
-    // https://github.com/llvm/llvm-project/issues/105978
-    if (cpu.arch.isArm() and query_abi.floatAbi() == .soft) {
-        cpu.features.removeFeature(@intFromEnum(Target.arm.Feature.vfp2));
-    }
+    // These CPU feature hacks have to come after ABI detection.
+    {
+        if (result.cpu.arch == .hexagon) {
+            // Both LLVM and LLD have broken support for the small data area. Yet LLVM has the
+            // feature on by default for all Hexagon CPUs. Clang sort of solves this by defaulting
+            // the `-gpsize` command line parameter for the Hexagon backend to 0, so that no
+            // constants get placed in the SDA. (This of course breaks down if the user passes
+            // `-G <n>` to Clang...) We can't do the `-gpsize` hack because we can have multiple
+            // concurrent LLVM emit jobs, and command line options in LLVM are shared globally. So
+            // just force this feature off. Lovely stuff.
+            result.cpu.features.removeFeature(@intFromEnum(Target.hexagon.Feature.small_data));
+        }
 
-    var result = try detectAbiAndDynamicLinker(cpu, os, query);
+        // https://github.com/llvm/llvm-project/issues/105978
+        if (result.cpu.arch.isArm() and result.abi.floatAbi() == .soft) {
+            result.cpu.features.removeFeature(@intFromEnum(Target.arm.Feature.vfp2));
+        }
+    }
 
     // It's possible that we detect the native ABI, but fail to detect the OS version or were told
     // to use the default OS version range. In that case, while we can't determine the exact native