--- /dev/null
+++ dyld/dyld-1340/mach_o/LinkerOptimizationHints.cpp
@@ -0,0 +1,128 @@
+/*
+ * Copyright (c) 2022 Apple Inc. All rights reserved.
+ *
+ * @APPLE_LICENSE_HEADER_START@
+ *
+ * This file contains Original Code and/or Modifications of Original Code
+ * as defined in and that are subject to the Apple Public Source License
+ * Version 2.0 (the 'License'). You may not use this file except in
+ * compliance with the License. Please obtain a copy of the License at
+ * http://www.opensource.apple.com/apsl/ and read it before using this
+ * file.
+ *
+ * The Original Code and all software distributed under the License are
+ * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
+ * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
+ * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
+ * Please see the License for the specific language governing rights and
+ * limitations under the License.
+ *
+ * @APPLE_LICENSE_HEADER_END@
+ */
+
+#include "LinkerOptimizationHints.h"
+#include "Fixups.h"
+#include "Misc.h"
+
+namespace mach_o {
+
+//
+// MARK: --- LinkerOptimizationHints inspection methods ---
+//
+
+LinkerOptimizationHints::LinkerOptimizationHints(std::span<const uint8_t> buffer)
+    : _buffer(buffer)
+{
+}
+
+Error LinkerOptimizationHints::forEachLOH(void (^callback)(Kind kind, std::span<uint64_t> addrs, bool& stop)) const
+{
+    std::span<const uint8_t> currentBuffer = _buffer;
+    while ( !currentBuffer.empty() ) {
+        bool malformed = false;
+        uint64_t kind = read_uleb128(currentBuffer, malformed);
+
+        if ( kind == 0 ) // padding at end of loh buffer
+            break;
+
+        if ( kind == -1 ) {
+            // FIXME: How do we want to get warnings from mach_o?
+            //warning("malformed uleb128 kind in LC_LINKER_OPTIMIZATION_HINTS");
+            break;
+        }
+        uint64_t count = read_uleb128(currentBuffer, malformed);
+        if ( count == -1 ) {
+            //warning("malformed uleb128 count in LC_LINKER_OPTIMIZATION_HINTS");
+            break;
+        }
+
+        if ( count == 0 ) {
+            //warning("malformed uleb128 count in LC_LINKER_OPTIMIZATION_HINTS");
+            break;
+        }
+
+        uint64_t addrs[count];
+        for (int32_t i=0; i < count; ++i) {
+            addrs[i] = read_uleb128(currentBuffer, malformed);
+        }
+
+        if ( malformed )
+            return Error("malformed uleb128");
+
+        bool stop = false;
+        switch ( (Kind)kind ) {
+            case Kind::unknown:
+                // these are known kinds, so do the callback
+                callback((Kind)kind, { &addrs[0], (uint32_t)count }, stop);
+                break;
+            default:
+                // unknown kind, so skip this one
+                break;
+        }
+
+        if ( stop )
+            break;
+    }
+
+    return Error::none();
+}
+
+static Error validFPAC(const char* name, std::span<const uint64_t> addrs,
+                       std::span<const uint32_t> segmentContent, std::span<const uint32_t> expectedContent)
+{
+    if ( addrs.size() != 5 ) {
+        return Error("Expected %s LOH to be 5 instructions.  Got %d", name, (uint32_t)addrs.size());
+    }
+
+    // The addresses should all point to subsequent instructions for now.  If this chages
+    // we'll need to update the below checks too
+    uint64_t baseAddr = addrs[0];
+    for ( uint32_t i = 0; i != 5; ++i ) {
+        if ( addrs[i] != (baseAddr + (i * 4)) ) {
+            return Error("Expected %s addresses to be contiguous.  Got element[%d] at address %lld", name, i, addrs[i]);
+        }
+    }
+
+    // Make sure the LOH fits in the buffer
+    if ( segmentContent.size() < 5 ) {
+        return Error("not enough space in segment for %s LOH. Got %d bytes", name, (uint32_t)segmentContent.size() * 4);
+    }
+
+    // Check the instructions are the right encodings for the above sequence
+    for ( uint32_t i = 0; i != 5; ++i ) {
+        if ( expectedContent[i] != segmentContent[i] ) {
+            return Error("Mismatched %s content. Expected elt[%d] to be 0x%x, got 0x%x", name, i, expectedContent[i], segmentContent[i]);
+        }
+    }
+
+    return Error::none();
+}
+
+Error LinkerOptimizationHints::valid(std::span<const MappedSegment> segments, uint64_t loadAddress) const
+{
+
+    return std::move(lohErr);
+}
+
+} // namespace mach_o