[lld] [LLD][COFF] Add basic ARM64X dynamic relocations support (PR #118035)

[Martin Storsjö via llvm-commits]

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@@ -1147,4 +1148,85 @@ uint32_t ImportThunkChunkARM64EC::extendRanges() {
   return sizeof(arm64Thunk) - sizeof(uint32_t);
 }
 
+size_t Arm64XDynamicRelocEntry::getSize() const {
+  switch (type) {
+  case IMAGE_DVRT_ARM64X_FIXUP_TYPE_VALUE:
+    return sizeof(uint16_t) + size; // A header and a payload.
+  case IMAGE_DVRT_ARM64X_FIXUP_TYPE_DELTA:
+  case IMAGE_DVRT_ARM64X_FIXUP_TYPE_ZEROFILL:
+    llvm_unreachable("unsupported type");
+  }
+}
+
+void Arm64XDynamicRelocEntry::writeTo(uint8_t *buf) const {
+  auto out = reinterpret_cast<ulittle16_t *>(buf);
+  *out = (offset & 0xfff) | (type << 12);
+
+  switch (type) {
+  case IMAGE_DVRT_ARM64X_FIXUP_TYPE_VALUE:
+    *out |= ((bit_width(size) - 1) << 14); // Encode the size.
+    switch (size) {
+    case 2:
+      out[1] = value;
+      break;
+    case 4:
+      *reinterpret_cast<ulittle32_t *>(out + 1) = value;
+      break;
+    case 8:
+      *reinterpret_cast<ulittle64_t *>(out + 1) = value;
+      break;
+    default:
+      llvm_unreachable("invalid size");
+    }
+    break;
+  case IMAGE_DVRT_ARM64X_FIXUP_TYPE_DELTA:
+  case IMAGE_DVRT_ARM64X_FIXUP_TYPE_ZEROFILL:
+    llvm_unreachable("unsupported type");
+  }
+}
+
+void DynamicRelocsChunk::finalize() {
+  llvm::stable_sort(arm64xRelocs, [=](const Arm64XDynamicRelocEntry &a,
+                                      const Arm64XDynamicRelocEntry &b) {
+    return a.offset < b.offset;
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mstorsjo wrote:

Ok, sounds reasonable - no need to move the sorting out in that case; keeping it together probably makes more sense indeed than to microoptimize such things at this stage.

https://github.com/llvm/llvm-project/pull/118035