bool is_tmp_usable(const IdomVector& idoms,
const SSATmp* tmp,
const Block* where) {
if (tmp->inst()->is(DefConst)) return true;
auto const definingBlock = findDefiningBlock(tmp, idoms);
if (!definingBlock) return false;
return dominates(definingBlock, where, idoms);
}
/*
* Build the CFG, then the dominator tree, then use it to validate SSA.
* 1. Each src must be defined by some other instruction, and each dst must
* be defined by the current instruction.
* 2. Each src must be defined earlier in the same block or in a dominator.
* 3. Each dst must not be previously defined.
* 4. Treat tmps defined by DefConst as always defined.
* 5. Each predecessor of a reachable block must be reachable (deleted
* blocks must not have out-edges to reachable blocks).
* 6. The entry block must not have any predecessors.
* 7. The entry block starts with a DefFP instruction.
*/
bool checkCfg(const IRUnit& unit) {
auto const blocksIds = rpoSortCfgWithIds(unit);
auto const& blocks = blocksIds.blocks;
jit::hash_set<const Edge*> edges;
// Entry block can't have predecessors.
always_assert(unit.entry()->numPreds() == 0);
// Entry block starts with DefFP
always_assert(!unit.entry()->empty() &&
unit.entry()->begin()->op() == DefFP);
// Check valid successor/predecessor edges.
for (Block* b : blocks) {
auto checkEdge = [&] (const Edge* e) {
always_assert(e->from() == b);
edges.insert(e);
for (auto& p : e->to()->preds()) if (&p == e) return;
always_assert(false); // did not find edge.
};
checkBlock(b);
if (auto *e = b->nextEdge()) checkEdge(e);
if (auto *e = b->takenEdge()) checkEdge(e);
}
for (Block* b : blocks) {
for (auto const &e : b->preds()) {
always_assert(&e == e.inst()->takenEdge() || &e == e.inst()->nextEdge());
always_assert(e.to() == b);
}
}
// Visit every instruction and make sure their sources are defined in a block
// that dominates the block containing the instruction.
auto const idoms = findDominators(unit, blocksIds);
forEachInst(blocks, [&] (const IRInstruction* inst) {
for (auto src : inst->srcs()) {
if (src->inst()->is(DefConst)) continue;
auto const dom = findDefiningBlock(src);
always_assert_flog(
dom && dominates(dom, inst->block(), idoms),
"src '{}' in '{}' came from '{}', which is not a "
"DefConst and is not defined at this use site",
src->toString(), inst->toString(),
src->inst()->toString()
);
}
});
return true;
}
