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8016696: PPC64 (part 4): add relocation for trampoline stubs

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A trampoline allows to encode a small branch in the code, even if there is the chance that this branch can not reach all possible code locations. If the relocation finds that a branch is too far for the instruction in the code, it can patch it to jump to the trampoline where is sufficient space for a far branch. Needed on PPC.

Reviewed-by: kvn, bdelsart, jrose
This commit is contained in:
Goetz Lindenmaier 2013-07-04 10:51:31 +02:00
parent 16f3142152
commit c12f5a0180
2 changed files with 77 additions and 2 deletions
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42
hotspot/src/share/vm/code/relocInfo.hpp
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@ -260,8 +260,8 @@ class relocInfo VALUE_OBJ_CLASS_SPEC {
poll_type = 10, // polling instruction for safepoints
poll_return_type = 11, // polling instruction for safepoints at return
metadata_type = 12, // metadata that used to be oops
yet_unused_type_1 = 13, // Still unused
yet_unused_type_2 = 14, // Still unused
trampoline_stub_type = 13, // stub-entry for trampoline
yet_unused_type_1 = 14, // Still unused
data_prefix_tag = 15, // tag for a prefix (carries data arguments)
type_mask = 15 // A mask which selects only the above values
};
@ -301,6 +301,7 @@ class relocInfo VALUE_OBJ_CLASS_SPEC {
visitor(poll) \
visitor(poll_return) \
visitor(section_word) \
visitor(trampoline_stub) \
public:
@ -1150,6 +1151,43 @@ class runtime_call_Relocation : public CallRelocation {
public:
};
// Trampoline Relocations.
// A trampoline allows to encode a small branch in the code, even if there
// is the chance that this branch can not reach all possible code locations.
// If the relocation finds that a branch is too far for the instruction
// in the code, it can patch it to jump to the trampoline where is
// sufficient space for a far branch. Needed on PPC.
class trampoline_stub_Relocation : public Relocation {
relocInfo::relocType type() { return relocInfo::trampoline_stub_type; }
public:
static RelocationHolder spec(address static_call) {
RelocationHolder rh = newHolder();
return (new (rh) trampoline_stub_Relocation(static_call));
}
private:
address _owner; // Address of the NativeCall that owns the trampoline.
trampoline_stub_Relocation(address owner) {
_owner = owner;
}
friend class RelocIterator;
trampoline_stub_Relocation() { }
public:
// Return the address of the NativeCall that owns the trampoline.
address owner() { return _owner; }
void pack_data_to(CodeSection * dest);
void unpack_data();
// Find the trampoline stub for a call.
static address get_trampoline_for(address call, nmethod* code);
};
class external_word_Relocation : public DataRelocation {
relocInfo::relocType type() { return relocInfo::external_word_type; }