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src/hotspot/share/cds/aotMetaspace.cpp

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1930   //  with narrow class pointers.
1931   // We reserve the whole range spanning both spaces, then split that range up.
1932 
1933   const size_t class_space_alignment = Metaspace::reserve_alignment();
1934 
1935   // When running with class space, requested archive base must satisfy both cds core alignment
1936   // and class space alignment.
1937   const size_t base_address_alignment = MAX2(class_space_alignment, archive_space_alignment);
1938   assert(is_aligned(base_address, base_address_alignment),
1939            "Archive base address unaligned: " PTR_FORMAT ", needs alignment: %zu.",
1940            p2i(base_address), base_address_alignment);
1941 
1942   size_t class_space_size = CompressedClassSpaceSize;
1943   assert(CompressedClassSpaceSize > 0 &&
1944          is_aligned(CompressedClassSpaceSize, class_space_alignment),
1945          "CompressedClassSpaceSize malformed: %zu", CompressedClassSpaceSize);
1946 
1947   const size_t ccs_begin_offset = align_up(archive_space_size, class_space_alignment);
1948   const size_t gap_size = ccs_begin_offset - archive_space_size;
1949 
1950   // Reduce class space size if it would not fit into the Klass encoding range
1951   constexpr size_t max_encoding_range_size = 4 * G;

1952   guarantee(archive_space_size < max_encoding_range_size - class_space_alignment, "Archive too large");
1953   if ((archive_space_size + gap_size + class_space_size) > max_encoding_range_size) {
1954     class_space_size = align_down(max_encoding_range_size - archive_space_size - gap_size, class_space_alignment);
1955     log_info(metaspace)("CDS initialization: reducing class space size from %zu to %zu",
1956         CompressedClassSpaceSize, class_space_size);
1957     FLAG_SET_ERGO(CompressedClassSpaceSize, class_space_size);
1958   }
1959 
1960   const size_t total_range_size =
1961       archive_space_size + gap_size + class_space_size;
1962 
1963   // Test that class space base address plus shift can be decoded by aarch64, when restored.
1964   const int precomputed_narrow_klass_shift = ArchiveBuilder::precomputed_narrow_klass_shift();
1965   if (!CompressedKlassPointers::check_klass_decode_mode(base_address, precomputed_narrow_klass_shift,
1966                                                         total_range_size)) {
1967     aot_log_info(aot)("CDS initialization: Cannot use SharedBaseAddress " PTR_FORMAT " with precomputed shift %d.",
1968                   p2i(base_address), precomputed_narrow_klass_shift);
1969     use_archive_base_addr = false;
1970   }
1971 

1930   //  with narrow class pointers.
1931   // We reserve the whole range spanning both spaces, then split that range up.
1932 
1933   const size_t class_space_alignment = Metaspace::reserve_alignment();
1934 
1935   // When running with class space, requested archive base must satisfy both cds core alignment
1936   // and class space alignment.
1937   const size_t base_address_alignment = MAX2(class_space_alignment, archive_space_alignment);
1938   assert(is_aligned(base_address, base_address_alignment),
1939            "Archive base address unaligned: " PTR_FORMAT ", needs alignment: %zu.",
1940            p2i(base_address), base_address_alignment);
1941 
1942   size_t class_space_size = CompressedClassSpaceSize;
1943   assert(CompressedClassSpaceSize > 0 &&
1944          is_aligned(CompressedClassSpaceSize, class_space_alignment),
1945          "CompressedClassSpaceSize malformed: %zu", CompressedClassSpaceSize);
1946 
1947   const size_t ccs_begin_offset = align_up(archive_space_size, class_space_alignment);
1948   const size_t gap_size = ccs_begin_offset - archive_space_size;
1949 
1950   // Reduce class space size if it would not fit into the maximum possible Klass encoding range. That
1951   // range is defined by the narrowKlass size.
1952   const size_t max_encoding_range_size = CompressedKlassPointers::max_klass_range_size();
1953   guarantee(archive_space_size < max_encoding_range_size - class_space_alignment, "Archive too large");
1954   if ((archive_space_size + gap_size + class_space_size) > max_encoding_range_size) {
1955     class_space_size = align_down(max_encoding_range_size - archive_space_size - gap_size, class_space_alignment);
1956     log_info(metaspace)("CDS initialization: reducing class space size from %zu to %zu",
1957         CompressedClassSpaceSize, class_space_size);
1958     FLAG_SET_ERGO(CompressedClassSpaceSize, class_space_size);
1959   }
1960 
1961   const size_t total_range_size =
1962       archive_space_size + gap_size + class_space_size;
1963 
1964   // Test that class space base address plus shift can be decoded by aarch64, when restored.
1965   const int precomputed_narrow_klass_shift = ArchiveBuilder::precomputed_narrow_klass_shift();
1966   if (!CompressedKlassPointers::check_klass_decode_mode(base_address, precomputed_narrow_klass_shift,
1967                                                         total_range_size)) {
1968     aot_log_info(aot)("CDS initialization: Cannot use SharedBaseAddress " PTR_FORMAT " with precomputed shift %d.",
1969                   p2i(base_address), precomputed_narrow_klass_shift);
1970     use_archive_base_addr = false;
1971   }
1972 
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