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Adding control flow simplification pass to compensate for lack of phi.

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This commit is contained in:
Ben Vanik
2014-08-06 14:19:42 -07:00
parent bba3315f58
commit b02ce5e95e
10 changed files with 187 additions and 8 deletions
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82
src/alloy/hir/hir_builder.cc
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@@ -436,6 +436,88 @@ void HIRBuilder::AddEdge(Block* src, Block* dest, uint32_t flags) {
dest->incoming_edge_head = edge;
}
void HIRBuilder::MergeAdjacentBlocks(Block* left, Block* right) {
assert_true(left->next == right && right->prev == left);
assert_true(!right->incoming_edge_head ||
right->incoming_edge_head->flags & Edge::DOMINATES);
// If the left block ends with a branch to the right block, drop it.
if (left->instr_tail &&
left->instr_tail->opcode->flags & OPCODE_FLAG_BRANCH) {
auto sig = left->instr_tail->opcode->signature;
if (GET_OPCODE_SIG_TYPE_SRC1(sig) == OPCODE_SIG_TYPE_L) {
if (left->instr_tail->src1.label->block == right) {
left->instr_tail->Remove();
}
}
if (GET_OPCODE_SIG_TYPE_SRC2(sig) == OPCODE_SIG_TYPE_L) {
if (left->instr_tail->src2.label->block == right) {
left->instr_tail->Remove();
}
}
}
// Walk through the right instructions and shift each one back into the left.
while (right->instr_head) {
auto instr = right->instr_head;
auto next = instr->next;
// Link into block list.
instr->next = nullptr;
instr->prev = left->instr_tail;
if (left->instr_tail) {
left->instr_tail->next = instr;
} else {
left->instr_head = left->instr_tail = instr;
}
left->instr_tail = instr;
// Unlink from old block list;
right->instr_head = next;
if (right->instr_tail == instr) {
right->instr_tail = nullptr;
}
if (next) {
next->prev = nullptr;
}
// Update state.
instr->block = left;
}
// Move/remove labels.
// We only need to preserve named labels.
while (right->label_head) {
auto label = right->label_head;
if (label->name) {
// Label is named - move it.
label->block = left;
label->prev = left->label_tail;
if (left->label_tail) {
left->label_tail->next = label;
}
left->label_tail = label;
if (!left->label_head) {
left->label_head = label;
}
}
right->label_head = label->next;
if (right->label_tail == label) {
right->label_tail = nullptr;
}
label->next = nullptr;
}
// Remove the right block from the block list.
left->next = right->next;
if (right->next) {
right->next->prev = left;
}
if (block_tail_ == right) {
block_tail_ = left;
}
}
Block* HIRBuilder::AppendBlock() {
Block* block = arena_->Alloc<Block>();
block->arena = arena_;