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8255338: CodeSections are never frozen 
Reviewed-by: neliasso, kvn
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@cl4es
cl4es committed Oct 23, 2020
1 parent cc86113 commit 185c8bc
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Showing 3 changed files with 2 additions and 81 deletions.
13 changes: 0 additions & 13 deletions src/hotspot/share/asm/assembler.cpp
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Expand Up @@ -199,19 +199,6 @@ void Label::patch_instructions(MacroAssembler* masm) {
continue;
}

#ifdef ASSERT
// Cross-section branches only work if the
// intermediate section boundaries are frozen.
if (target_sect != branch_sect) {
for (int n = MIN2(target_sect, branch_sect),
nlimit = (target_sect + branch_sect) - n;
n < nlimit; n++) {
CodeSection* cs = cb->code_section(n);
assert(cs->is_frozen(), "cross-section branch needs stable offsets");
}
}
#endif //ASSERT

// Push the target offset into the branch instruction.
masm->pd_patch_instruction(branch, target, file, line);
}
Expand Down
42 changes: 2 additions & 40 deletions src/hotspot/share/asm/codeBuffer.cpp
View file
Expand Up @@ -176,28 +176,6 @@ void CodeBuffer::initialize_section_size(CodeSection* cs, csize_t size) {
if (_insts.has_locs()) cs->initialize_locs(1);
}

void CodeBuffer::freeze_section(CodeSection* cs) {
CodeSection* next_cs = (cs == consts())? NULL: code_section(cs->index()+1);
csize_t frozen_size = cs->size();
if (next_cs != NULL) {
frozen_size = next_cs->align_at_start(frozen_size);
}
address old_limit = cs->limit();
address new_limit = cs->start() + frozen_size;
relocInfo* old_locs_limit = cs->locs_limit();
relocInfo* new_locs_limit = cs->locs_end();
// Patch the limits.
cs->_limit = new_limit;
cs->_locs_limit = new_locs_limit;
cs->_frozen = true;
if (next_cs != NULL && !next_cs->is_allocated() && !next_cs->is_frozen()) {
// Give remaining buffer space to the following section.
next_cs->initialize(new_limit, old_limit - new_limit);
next_cs->initialize_shared_locs(new_locs_limit,
old_locs_limit - new_locs_limit);
}
}

void CodeBuffer::set_blob(BufferBlob* blob) {
_blob = blob;
if (blob != NULL) {
Expand Down Expand Up @@ -501,18 +479,6 @@ void CodeBuffer::compute_final_layout(CodeBuffer* dest) const {
} else {
guarantee(padding == 0, "In first iteration no padding should be needed.");
}
#ifdef ASSERT
if (prev_cs != NULL && prev_cs->is_frozen() && n < (SECT_LIMIT - 1)) {
// Make sure the ends still match up.
// This is important because a branch in a frozen section
// might target code in a following section, via a Label,
// and without a relocation record. See Label::patch_instructions.
address dest_start = buf+buf_offset;
csize_t start2start = cs->start() - prev_cs->start();
csize_t dest_start2start = dest_start - prev_dest_cs->start();
assert(start2start == dest_start2start, "cannot stretch frozen sect");
}
#endif //ASSERT
prev_dest_cs = dest_cs;
prev_cs = cs;
}
Expand Down Expand Up @@ -891,9 +857,6 @@ void CodeBuffer::expand(CodeSection* which_cs, csize_t amount) {
// Resizing must be allowed
{
if (blob() == NULL) return; // caller must check for blob == NULL
for (int n = 0; n < (int)SECT_LIMIT; n++) {
guarantee(!code_section(n)->is_frozen(), "resizing not allowed when frozen");
}
}

// Figure new capacity for each section.
Expand Down Expand Up @@ -1219,9 +1182,8 @@ void CodeBuffer::decode() {

void CodeSection::print(const char* name) {
csize_t locs_size = locs_end() - locs_start();
tty->print_cr(" %7s.code = " PTR_FORMAT " : " PTR_FORMAT " : " PTR_FORMAT " (%d of %d)%s",
name, p2i(start()), p2i(end()), p2i(limit()), size(), capacity(),
is_frozen()? " [frozen]": "");
tty->print_cr(" %7s.code = " PTR_FORMAT " : " PTR_FORMAT " : " PTR_FORMAT " (%d of %d)",
name, p2i(start()), p2i(end()), p2i(limit()), size(), capacity());
tty->print_cr(" %7s.locs = " PTR_FORMAT " : " PTR_FORMAT " : " PTR_FORMAT " (%d of %d) point=%d",
name, p2i(locs_start()), p2i(locs_end()), p2i(locs_limit()), locs_size, locs_capacity(), locs_point_off());
if (PrintRelocations) {
Expand Down
28 changes: 0 additions & 28 deletions src/hotspot/share/asm/codeBuffer.hpp
View file
Expand Up @@ -92,7 +92,6 @@ class CodeSection {
relocInfo* _locs_limit; // first byte after relocation information buf
address _locs_point; // last relocated position (grows upward)
bool _locs_own; // did I allocate the locs myself?
bool _frozen; // no more expansion of this section
bool _scratch_emit; // Buffer is used for scratch emit, don't relocate.
char _index; // my section number (SECT_INST, etc.)
CodeBuffer* _outer; // enclosing CodeBuffer
Expand All @@ -109,7 +108,6 @@ class CodeSection {
_locs_limit = NULL;
_locs_point = NULL;
_locs_own = false;
_frozen = false;
_scratch_emit = false;
debug_only(_index = (char)-1);
debug_only(_outer = (CodeBuffer*)badAddress);
Expand Down Expand Up @@ -161,12 +159,10 @@ class CodeSection {
address locs_point() const { return _locs_point; }
csize_t locs_point_off() const{ return (csize_t)(_locs_point - _start); }
csize_t locs_capacity() const { return (csize_t)(_locs_limit - _locs_start); }
csize_t locs_remaining()const { return (csize_t)(_locs_limit - _locs_end); }

int index() const { return _index; }
bool is_allocated() const { return _start != NULL; }
bool is_empty() const { return _start == _end; }
bool is_frozen() const { return _frozen; }
bool has_locs() const { return _locs_end != NULL; }

// Mark scratch buffer.
Expand All @@ -184,8 +180,6 @@ class CodeSection {
void set_end(address pc) { assert(allocates2(pc), "not in CodeBuffer memory: " INTPTR_FORMAT " <= " INTPTR_FORMAT " <= " INTPTR_FORMAT, p2i(_start), p2i(pc), p2i(_limit)); _end = pc; }
void set_mark(address pc) { assert(contains2(pc), "not in codeBuffer");
_mark = pc; }
void set_mark_off(int offset) { assert(contains2(offset+_start),"not in codeBuffer");
_mark = offset + _start; }
void set_mark() { _mark = _end; }
void clear_mark() { _mark = NULL; }

Expand Down Expand Up @@ -259,10 +253,6 @@ class CodeSection {

csize_t align_at_start(csize_t off) const { return (csize_t) align_up(off, alignment()); }

// Mark a section frozen. Assign its remaining space to
// the following section. It will never expand after this point.
inline void freeze(); // { _outer->freeze_section(this); }

// Ensure there's enough space left in the current section.
// Return true if there was an expansion.
bool maybe_expand_to_ensure_remaining(csize_t amount);
Expand Down Expand Up @@ -463,8 +453,6 @@ class CodeBuffer: public StackObj {

void initialize_section_size(CodeSection* cs, csize_t size);

void freeze_section(CodeSection* cs);

// helper for CodeBuffer::expand()
void take_over_code_from(CodeBuffer* cs);

Expand Down Expand Up @@ -577,10 +565,8 @@ class CodeBuffer: public StackObj {
address insts_begin() const { return _insts.start(); }
address insts_end() const { return _insts.end(); }
void set_insts_end(address end) { _insts.set_end(end); }
address insts_limit() const { return _insts.limit(); }
address insts_mark() const { return _insts.mark(); }
void set_insts_mark() { _insts.set_mark(); }
void clear_insts_mark() { _insts.clear_mark(); }

// is there anything in the buffer other than the current section?
bool is_pure() const { return insts_size() == total_content_size(); }
Expand Down Expand Up @@ -652,12 +638,6 @@ class CodeBuffer: public StackObj {
_code_strings.free(); // sets _strings Null as a side-effect.
}
}

// Print the comment associated with offset on stream, if there is one.
virtual void print_block_comment(outputStream* stream, address block_begin) {
intptr_t offset = (intptr_t)(block_begin - _total_start); // I assume total_start is not correct for all code sections.
_code_strings.print_block_comment(stream, offset);
}
#endif

// Code generation
Expand All @@ -683,9 +663,6 @@ class CodeBuffer: public StackObj {
}
}

// Transform an address from the code in this code buffer to a specified code buffer
address transform_address(const CodeBuffer &cb, address addr) const;

void block_comment(intptr_t offset, const char * comment) PRODUCT_RETURN;
const char* code_string(const char* str) PRODUCT_RETURN_(return NULL;);

Expand Down Expand Up @@ -714,11 +691,6 @@ class CodeBuffer: public StackObj {

};


inline void CodeSection::freeze() {
_outer->freeze_section(this);
}

inline bool CodeSection::maybe_expand_to_ensure_remaining(csize_t amount) {
if (remaining() < amount) { _outer->expand(this, amount); return true; }
return false;
Expand Down

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