/*
* Look for Jcc instructions in the main trace that
* branch to "normal exits". We can optimize these into the
* SideExitJcc* instructions that can be patched in place.
*/
void optimizeSideExitJccs(IRUnit& unit) {
auto trace = unit.main();
FTRACE(5, "SideExitJcc:vvvvvvvvvvvvvvvvvvvvv\n");
SCOPE_EXIT { FTRACE(5, "SideExitJcc:^^^^^^^^^^^^^^^^^^^^^\n"); };
forEachInst(trace->blocks(), [&] (IRInstruction* inst) {
if (!jccCanBeDirectExit(inst->op())) return;
auto const exitBlock = inst->taken();
if (!isNormalExit(exitBlock)) return;
auto it = exitBlock->backIter();
auto& reqBindJmp = *(it--);
auto& syncABI = *it;
assert(syncABI.op() == SyncABIRegs);
FTRACE(5, "converting jcc ({}) to side exit\n",
inst->id());
auto const newOpcode = jmpToSideExitJmp(inst->op());
SideExitJccData data;
data.taken = reqBindJmp.extra<ReqBindJmp>()->offset;
auto const block = inst->block();
block->insert(block->iteratorTo(inst),
unit.cloneInstruction(&syncABI));
unit.replace(
inst,
newOpcode,
data,
std::make_pair(inst->numSrcs(), inst->srcs().begin())
);
});
}
/*
* Branch is a conditional branch to a normal exit. Convert it
* into a SideExitJcc instruction that can be patched in place.
*/
void optimizeSideExitJcc(IRUnit& unit, IRInstruction* inst, Block* exitBlock) {
assert(isSideExitJcc(inst, exitBlock));
FTRACE(5, "SideExitJcc:vvvvvvvvvvvvvvvvvvvvv\n");
SCOPE_EXIT { FTRACE(5, "SideExitJcc:^^^^^^^^^^^^^^^^^^^^^\n"); };
auto it = exitBlock->backIter();
auto& reqBindJmp = *(it--);
auto& syncABI = *it;
assert(syncABI.op() == SyncABIRegs);
FTRACE(5, "converting jcc ({}) to side exit\n",
inst->id());
auto const newOpcode = jmpToSideExitJmp(inst->op());
SideExitJccData data;
data.taken = reqBindJmp.extra<ReqBindJmp>()->offset;
data.trflags = reqBindJmp.extra<ReqBindJmp>()->trflags;
auto const block = inst->block();
block->insert(block->iteratorTo(inst),
unit.cloneInstruction(&syncABI));
auto next = inst->next();
unit.replace(
inst,
newOpcode,
data,
std::make_pair(inst->numSrcs(), inst->srcs().begin())
);
block->push_back(unit.gen(Jmp, inst->marker(), next));
}
