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8329433: Reduce nmethod header size #18768

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8329433: Reduce nmethod header size #18768

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a0c46b8
8329433: Reduce nmethod header size
vnkozlov Apr 12, 2024
488f1b9
Moved some fields initialization into init_defaults()
vnkozlov Apr 15, 2024
13744e7
Union fields which usages do not overlap
vnkozlov Apr 15, 2024
6cb22e8
Use 16-bits types for header_size and frame_complete_offset arguments
vnkozlov Apr 16, 2024
8405a23
Address comments. Used checked_cast.
vnkozlov Apr 16, 2024
71ade0f
Shuffle fields initialization
vnkozlov Apr 17, 2024
6a164b1
remove trailing space
vnkozlov Apr 17, 2024
adc1759
Merge master
vnkozlov Apr 17, 2024
5f5f30d
Address comment
vnkozlov Apr 17, 2024
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4 changes: 1 addition & 3 deletions src/hotspot/share/code/nmethod.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -999,7 +999,6 @@ const char* nmethod::compiler_name() const {
// Fill in default values for various flag fields
void nmethod::init_defaults() {
// avoid uninitialized fields, even for short time periods
_osr_link = nullptr;
_exception_cache = nullptr;
_gc_data = nullptr;
_oops_do_mark_link = nullptr;
Expand Down Expand Up @@ -1368,8 +1367,7 @@ nmethod::nmethod(
offsets->value(CodeOffsets::Frame_Complete), frame_size, oop_maps, false),
_deoptimization_generation(0),
_method(method),
_native_receiver_sp_offset(in_ByteSize(-1)),
_native_basic_lock_sp_offset(in_ByteSize(-1))
_osr_link(nullptr)
{
assert(debug_info->oop_recorder() == code_buffer->oop_recorder(), "shared OR");
{
Expand Down
30 changes: 17 additions & 13 deletions src/hotspot/share/code/nmethod.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -188,8 +188,23 @@ class nmethod : public CodeBlob {

Method* _method;

// To support simple linked-list chaining of nmethods:
nmethod* _osr_link; // from InstanceKlass::osr_nmethods_head
// To reduce header size union fields which usages do not overlap.
union {
// To support simple linked-list chaining of nmethods:
nmethod* _osr_link; // from InstanceKlass::osr_nmethods_head
struct {
// These are used for compiled synchronized native methods to
// locate the owner and stack slot for the BasicLock. They are
// needed because there is no debug information for compiled native
// wrappers and the oop maps are insufficient to allow
// frame::retrieve_receiver() to work. Currently they are expected
// to be byte offsets from the Java stack pointer for maximum code
// sharing between platforms. JVMTI's GetLocalInstance() uses these
// offsets to find the receiver for non-static native wrapper frames.
ByteSize _native_receiver_sp_offset;
ByteSize _native_basic_lock_sp_offset;
};
};

PcDescContainer _pc_desc_container;
ExceptionCache* volatile _exception_cache;
Expand Down Expand Up @@ -241,17 +256,6 @@ class nmethod : public CodeBlob {
// pc during a deopt.
int _orig_pc_offset;

// These are used for compiled synchronized native methods to
// locate the owner and stack slot for the BasicLock. They are
// needed because there is no debug information for compiled native
// wrappers and the oop maps are insufficient to allow
// frame::retrieve_receiver() to work. Currently they are expected
// to be byte offsets from the Java stack pointer for maximum code
// sharing between platforms. JVMTI's GetLocalInstance() uses these
// offsets to find the receiver for non-static native wrapper frames.
ByteSize _native_receiver_sp_offset;
ByteSize _native_basic_lock_sp_offset;

int _compile_id; // which compilation made this nmethod
CompLevel _comp_level; // compilation level (s1)
CompilerType _compiler_type; // which compiler made this nmethod (u1)
Expand Down