/*
* 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())
);
});
}
/*
* Look for CheckStk/CheckLoc instructions in the main trace that
* branch to "normal exits". We can optimize these into the
* SideExitGuard* instructions that can be patched in place.
*/
void optimizeSideExitChecks(IRUnit& unit) {
auto trace = unit.main();
FTRACE(5, "SideExit:vvvvvvvvvvvvvvvvvvvvv\n");
SCOPE_EXIT { FTRACE(5, "SideExit:^^^^^^^^^^^^^^^^^^^^^\n"); };
forEachInst(trace->blocks(), [&] (IRInstruction* inst) {
if (inst->op() != CheckStk && inst->op() != CheckLoc) return;
auto const exitBlock = inst->taken();
if (!isNormalExit(exitBlock)) return;
auto const syncABI = &*boost::prior(exitBlock->backIter());
assert(syncABI->op() == SyncABIRegs);
FTRACE(5, "converting jump ({}) to side exit\n",
inst->id());
auto const isStack = inst->op() == CheckStk;
auto const fp = syncABI->src(0);
auto const sp = syncABI->src(1);
SideExitGuardData data;
data.checkedSlot = isStack
? inst->extra<CheckStk>()->offset
: inst->extra<CheckLoc>()->locId;
data.taken = exitBlock->back()->extra<ReqBindJmp>()->offset;
auto const block = inst->block();
block->insert(block->iteratorTo(inst),
unit.cloneInstruction(syncABI));
unit.replace(
inst,
isStack ? SideExitGuardStk : SideExitGuardLoc,
inst->typeParam(),
data,
isStack ? sp : fp
);
});
}
// Return true if branch is a conditional branch to a normal exit.
bool isSideExitJcc(IRInstruction* branch, Block* exit) {
return jccCanBeDirectExit(branch->op()) && isNormalExit(exit);
}
