mirror of
https://github.com/odin-lang/Odin.git
synced 2026-02-18 08:58:23 +00:00
494 lines
11 KiB
C
494 lines
11 KiB
C
// Optimizations for the SSA code
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void ssa_opt_add_operands(ssaValueArray *ops, ssaInstr *i) {
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switch (i->kind) {
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case ssaInstr_Comment:
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break;
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case ssaInstr_Local:
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break;
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case ssaInstr_ZeroInit:
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array_add(ops, i->ZeroInit.address);
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break;
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case ssaInstr_Store:
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array_add(ops, i->Store.address);
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array_add(ops, i->Store.value);
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break;
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case ssaInstr_Load:
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array_add(ops, i->Load.address);
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break;
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case ssaInstr_ArrayElementPtr:
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array_add(ops, i->ArrayElementPtr.address);
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array_add(ops, i->ArrayElementPtr.elem_index);
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break;
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case ssaInstr_StructElementPtr:
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array_add(ops, i->StructElementPtr.address);
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break;
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case ssaInstr_PtrOffset:
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array_add(ops, i->PtrOffset.address);
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array_add(ops, i->PtrOffset.offset);
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break;
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case ssaInstr_ArrayExtractValue:
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array_add(ops, i->ArrayExtractValue.address);
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break;
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case ssaInstr_StructExtractValue:
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array_add(ops, i->StructExtractValue.address);
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break;
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case ssaInstr_Conv:
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array_add(ops, i->Conv.value);
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break;
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case ssaInstr_Jump:
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break;
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case ssaInstr_If:
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array_add(ops, i->If.cond);
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break;
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case ssaInstr_Return:
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if (i->Return.value != NULL) {
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array_add(ops, i->Return.value);
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}
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break;
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case ssaInstr_Select:
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array_add(ops, i->Select.cond);
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break;
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case ssaInstr_Phi:
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for_array(j, i->Phi.edges) {
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array_add(ops, i->Phi.edges.e[j]);
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}
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break;
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case ssaInstr_Unreachable: break;
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case ssaInstr_BinaryOp:
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array_add(ops, i->BinaryOp.left);
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array_add(ops, i->BinaryOp.right);
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break;
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case ssaInstr_Call:
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array_add(ops, i->Call.value);
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for (isize j = 0; j < i->Call.arg_count; j++) {
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array_add(ops, i->Call.args[j]);
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}
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break;
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case ssaInstr_VectorExtractElement:
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array_add(ops, i->VectorExtractElement.vector);
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array_add(ops, i->VectorExtractElement.index);
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break;
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case ssaInstr_VectorInsertElement:
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array_add(ops, i->VectorInsertElement.vector);
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array_add(ops, i->VectorInsertElement.elem);
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array_add(ops, i->VectorInsertElement.index);
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break;
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case ssaInstr_VectorShuffle:
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array_add(ops, i->VectorShuffle.vector);
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break;
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case ssaInstr_StartupRuntime:
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break;
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case ssaInstr_BoundsCheck:
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array_add(ops, i->BoundsCheck.index);
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array_add(ops, i->BoundsCheck.len);
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break;
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case ssaInstr_SliceBoundsCheck:
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array_add(ops, i->SliceBoundsCheck.low);
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array_add(ops, i->SliceBoundsCheck.high);
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array_add(ops, i->SliceBoundsCheck.max);
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break;
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}
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}
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void ssa_opt_block_replace_pred(ssaBlock *b, ssaBlock *from, ssaBlock *to) {
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for_array(i, b->preds) {
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ssaBlock *pred = b->preds.e[i];
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if (pred == from) {
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b->preds.e[i] = to;
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}
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}
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}
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void ssa_opt_block_replace_succ(ssaBlock *b, ssaBlock *from, ssaBlock *to) {
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for_array(i, b->succs) {
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ssaBlock *succ = b->succs.e[i];
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if (succ == from) {
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b->succs.e[i] = to;
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}
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}
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}
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bool ssa_opt_block_has_phi(ssaBlock *b) {
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return b->instrs.e[0]->Instr.kind == ssaInstr_Phi;
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}
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ssaValueArray ssa_get_block_phi_nodes(ssaBlock *b) {
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ssaValueArray phis = {0};
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for_array(i, b->instrs) {
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ssaInstr *instr = &b->instrs.e[i]->Instr;
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if (instr->kind != ssaInstr_Phi) {
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phis = b->instrs;
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phis.count = i;
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return phis;
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}
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}
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return phis;
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}
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void ssa_remove_pred(ssaBlock *b, ssaBlock *p) {
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ssaValueArray phis = ssa_get_block_phi_nodes(b);
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isize i = 0;
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for_array(j, b->preds) {
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ssaBlock *pred = b->preds.e[j];
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if (pred != p) {
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b->preds.e[i] = b->preds.e[j];
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for_array(k, phis) {
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ssaInstrPhi *phi = &phis.e[k]->Instr.Phi;
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phi->edges.e[i] = phi->edges.e[j];
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}
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i++;
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}
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}
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b->preds.count = i;
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for_array(k, phis) {
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ssaInstrPhi *phi = &phis.e[k]->Instr.Phi;
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phi->edges.count = i;
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}
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}
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void ssa_remove_dead_blocks(ssaProcedure *proc) {
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isize j = 0;
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for_array(i, proc->blocks) {
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ssaBlock *b = proc->blocks.e[i];
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if (b == NULL) {
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continue;
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}
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// NOTE(bill): Swap order
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b->index = j;
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proc->blocks.e[j++] = b;
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}
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proc->blocks.count = j;
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}
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void ssa_mark_reachable(ssaBlock *b) {
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isize const WHITE = 0;
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isize const BLACK = -1;
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b->index = BLACK;
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for_array(i, b->succs) {
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ssaBlock *succ = b->succs.e[i];
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if (succ->index == WHITE) {
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ssa_mark_reachable(succ);
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}
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}
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}
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void ssa_remove_unreachable_blocks(ssaProcedure *proc) {
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isize const WHITE = 0;
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isize const BLACK = -1;
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for_array(i, proc->blocks) {
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proc->blocks.e[i]->index = WHITE;
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}
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ssa_mark_reachable(proc->blocks.e[0]);
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for_array(i, proc->blocks) {
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ssaBlock *b = proc->blocks.e[i];
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if (b->index == WHITE) {
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for_array(j, b->succs) {
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ssaBlock *c = b->succs.e[j];
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if (c->index == BLACK) {
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ssa_remove_pred(c, b);
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}
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}
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// NOTE(bill): Mark as empty but don't actually free it
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// As it's been allocated with an arena
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proc->blocks.e[i] = NULL;
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}
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}
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ssa_remove_dead_blocks(proc);
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}
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bool ssa_opt_block_fusion(ssaProcedure *proc, ssaBlock *a) {
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if (a->succs.count != 1) {
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return false;
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}
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ssaBlock *b = a->succs.e[0];
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if (b->preds.count != 1) {
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return false;
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}
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if (ssa_opt_block_has_phi(b)) {
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return false;
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}
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array_pop(&a->instrs); // Remove branch at end
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for_array(i, b->instrs) {
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array_add(&a->instrs, b->instrs.e[i]);
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ssa_set_instr_parent(b->instrs.e[i], a);
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}
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array_clear(&a->succs);
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for_array(i, b->succs) {
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array_add(&a->succs, b->succs.e[i]);
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}
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// Fix preds links
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for_array(i, b->succs) {
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ssa_opt_block_replace_pred(b->succs.e[i], b, a);
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}
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proc->blocks.e[b->index] = NULL;
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return true;
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}
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void ssa_opt_blocks(ssaProcedure *proc) {
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ssa_remove_unreachable_blocks(proc);
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#if 1
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bool changed = true;
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while (changed) {
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changed = false;
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for_array(i, proc->blocks) {
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ssaBlock *b = proc->blocks.e[i];
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if (b == NULL) {
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continue;
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}
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GB_ASSERT(b->index == i);
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if (ssa_opt_block_fusion(proc, b)) {
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changed = true;
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}
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// TODO(bill): other simple block optimizations
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}
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}
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#endif
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ssa_remove_dead_blocks(proc);
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}
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void ssa_opt_build_referrers(ssaProcedure *proc) {
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gbTempArenaMemory tmp = gb_temp_arena_memory_begin(&proc->module->tmp_arena);
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ssaValueArray ops = {0}; // NOTE(bill): Act as a buffer
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array_init_reserve(&ops, proc->module->tmp_allocator, 64); // HACK(bill): This _could_ overflow the temp arena
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for_array(i, proc->blocks) {
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ssaBlock *b = proc->blocks.e[i];
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for_array(j, b->instrs) {
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ssaValue *instr = b->instrs.e[j];
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array_clear(&ops);
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ssa_opt_add_operands(&ops, &instr->Instr);
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for_array(k, ops) {
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ssaValue *op = ops.e[k];
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if (op == NULL) {
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continue;
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}
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ssaValueArray *refs = ssa_value_referrers(op);
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if (refs != NULL) {
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array_add(refs, instr);
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}
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}
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}
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}
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gb_temp_arena_memory_end(tmp);
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}
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// State of Lengauer-Tarjan algorithm
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// Based on this paper: http://jgaa.info/accepted/2006/GeorgiadisTarjanWerneck2006.10.1.pdf
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typedef struct ssaLTState {
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isize count;
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// NOTE(bill): These are arrays
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ssaBlock **sdom; // Semidominator
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ssaBlock **parent; // Parent in DFS traversal of CFG
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ssaBlock **ancestor;
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} ssaLTState;
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// §2.2 - bottom of page
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void ssa_lt_link(ssaLTState *lt, ssaBlock *p, ssaBlock *q) {
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lt->ancestor[q->index] = p;
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}
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i32 ssa_lt_depth_first_search(ssaLTState *lt, ssaBlock *p, i32 i, ssaBlock **preorder) {
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preorder[i] = p;
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p->dom.pre = i++;
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lt->sdom[p->index] = p;
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ssa_lt_link(lt, NULL, p);
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for_array(index, p->succs) {
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ssaBlock *q = p->succs.e[index];
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if (lt->sdom[q->index] == NULL) {
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lt->parent[q->index] = p;
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i = ssa_lt_depth_first_search(lt, q, i, preorder);
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}
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}
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return i;
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}
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ssaBlock *ssa_lt_eval(ssaLTState *lt, ssaBlock *v) {
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ssaBlock *u = v;
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for (;
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lt->ancestor[v->index] != NULL;
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v = lt->ancestor[v->index]) {
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if (lt->sdom[v->index]->dom.pre < lt->sdom[u->index]->dom.pre) {
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u = v;
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}
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}
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return u;
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}
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typedef struct ssaDomPrePost {
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i32 pre, post;
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} ssaDomPrePost;
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ssaDomPrePost ssa_opt_number_dom_tree(ssaBlock *v, i32 pre, i32 post) {
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ssaDomPrePost result = {pre, post};
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v->dom.pre = pre++;
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for_array(i, v->dom.children) {
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result = ssa_opt_number_dom_tree(v->dom.children.e[i], result.pre, result.post);
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}
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v->dom.post = post++;
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result.pre = pre;
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result.post = post;
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return result;
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}
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// NOTE(bill): Requires `ssa_opt_blocks` to be called before this
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void ssa_opt_build_dom_tree(ssaProcedure *proc) {
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// Based on this paper: http://jgaa.info/accepted/2006/GeorgiadisTarjanWerneck2006.10.1.pdf
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gbTempArenaMemory tmp = gb_temp_arena_memory_begin(&proc->module->tmp_arena);
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isize n = proc->blocks.count;
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ssaBlock **buf = gb_alloc_array(proc->module->tmp_allocator, ssaBlock *, 5*n);
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ssaLTState lt = {0};
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lt.count = n;
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lt.sdom = &buf[0*n];
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lt.parent = &buf[1*n];
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lt.ancestor = &buf[2*n];
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ssaBlock **preorder = &buf[3*n];
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ssaBlock **buckets = &buf[4*n];
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ssaBlock *root = proc->blocks.e[0];
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// Step 1 - number vertices
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i32 pre_num = ssa_lt_depth_first_search(<, root, 0, preorder);
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gb_memmove(buckets, preorder, n*gb_size_of(preorder[0]));
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for (i32 i = n-1; i > 0; i--) {
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ssaBlock *w = preorder[i];
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// Step 3 - Implicitly define idom for nodes
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for (ssaBlock *v = buckets[i]; v != w; v = buckets[v->dom.pre]) {
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ssaBlock *u = ssa_lt_eval(<, v);
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if (lt.sdom[u->index]->dom.pre < i) {
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v->dom.idom = u;
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} else {
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v->dom.idom = w;
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}
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}
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// Step 2 - Compute all sdoms
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lt.sdom[w->index] = lt.parent[w->index];
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for_array(pred_index, w->preds) {
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ssaBlock *v = w->preds.e[pred_index];
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ssaBlock *u = ssa_lt_eval(<, v);
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if (lt.sdom[u->index]->dom.pre < lt.sdom[w->index]->dom.pre) {
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lt.sdom[w->index] = lt.sdom[u->index];
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}
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}
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ssa_lt_link(<, lt.parent[w->index], w);
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if (lt.parent[w->index] == lt.sdom[w->index]) {
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w->dom.idom = lt.parent[w->index];
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} else {
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buckets[i] = buckets[lt.sdom[w->index]->dom.pre];
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buckets[lt.sdom[w->index]->dom.pre] = w;
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}
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}
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// The rest of Step 3
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for (ssaBlock *v = buckets[0]; v != root; v = buckets[v->dom.pre]) {
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v->dom.idom = root;
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}
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// Step 4 - Explicitly define idom for nodes (in preorder)
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for (isize i = 1; i < n; i++) {
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ssaBlock *w = preorder[i];
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if (w == root) {
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w->dom.idom = NULL;
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} else {
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// Weird tree relationships here!
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if (w->dom.idom != lt.sdom[w->index]) {
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w->dom.idom = w->dom.idom->dom.idom;
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}
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// Calculate children relation as inverse of idom
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if (w->dom.idom->dom.children.e == NULL) {
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// TODO(bill): Is this good enough for memory allocations?
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array_init(&w->dom.idom->dom.children, heap_allocator());
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}
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array_add(&w->dom.idom->dom.children, w);
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}
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}
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ssa_opt_number_dom_tree(root, 0, 0);
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gb_temp_arena_memory_end(tmp);
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}
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void ssa_opt_mem2reg(ssaProcedure *proc) {
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// TODO(bill): ssa_opt_mem2reg
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}
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void ssa_opt_tree(ssaGen *s) {
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s->opt_called = true;
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for_array(member_index, s->module.procs) {
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ssaProcedure *proc = s->module.procs.e[member_index];
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if (proc->blocks.count == 0) { // Prototype/external procedure
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continue;
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}
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ssa_opt_blocks(proc);
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#if 1
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ssa_opt_build_referrers(proc);
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ssa_opt_build_dom_tree(proc);
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// TODO(bill): ssa optimization
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// [ ] cse (common-subexpression) elim
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// [ ] copy elim
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// [ ] dead code elim
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// [ ] dead store/load elim
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// [ ] phi elim
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// [ ] short circuit elim
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// [ ] bounds check elim
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// [ ] lift/mem2reg
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// [ ] lift/mem2reg
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ssa_opt_mem2reg(proc);
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#endif
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GB_ASSERT(proc->blocks.count > 0);
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ssa_number_proc_registers(proc);
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}
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}
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