| 1 | //! Bounds Check Elimination (BCE). |
| 2 | //! |
| 3 | //! Removes `RuntimeCall(CheckBounds, [index, lower, upper])` calls |
| 4 | //! when the index can be proven in-bounds. At O2+, this eliminates |
| 5 | //! the overhead of runtime bounds checking for safe array accesses. |
| 6 | //! |
| 7 | //! Safe patterns: |
| 8 | //! - Loop IV in a counted loop with bounds [lo, hi] where lo >= lower |
| 9 | //! and hi <= upper |
| 10 | //! - Constant index within [lower, upper] |
| 11 | //! |
| 12 | //! Bounds checks are inserted during lowering for scalar array |
| 13 | //! element accesses. This pass removes the checks when the index is |
| 14 | //! provably safe. |
| 15 | |
| 16 | use super::loop_utils::{find_preheader, resolve_const_int}; |
| 17 | use super::pass::Pass; |
| 18 | use crate::ir::inst::*; |
| 19 | use crate::ir::walk::{find_natural_loops, predecessors}; |
| 20 | |
| 21 | pub struct Bce; |
| 22 | |
| 23 | impl Pass for Bce { |
| 24 | fn name(&self) -> &'static str { |
| 25 | "bce" |
| 26 | } |
| 27 | |
| 28 | fn run(&self, module: &mut Module) -> bool { |
| 29 | let mut changed = false; |
| 30 | for func in &mut module.functions { |
| 31 | if bce_function(func) { |
| 32 | changed = true; |
| 33 | } |
| 34 | } |
| 35 | changed |
| 36 | } |
| 37 | } |
| 38 | |
| 39 | fn bce_function(func: &mut Function) -> bool { |
| 40 | let loops = find_natural_loops(func); |
| 41 | let preds = predecessors(func); |
| 42 | let mut to_remove: Vec<(BlockId, usize)> = Vec::new(); |
| 43 | |
| 44 | for block in &func.blocks { |
| 45 | for (inst_idx, inst) in block.insts.iter().enumerate() { |
| 46 | if let InstKind::RuntimeCall(RuntimeFunc::CheckBounds, args) = &inst.kind { |
| 47 | if args.len() == 3 { |
| 48 | let index = args[0]; |
| 49 | let lower = args[1]; |
| 50 | let upper = args[2]; |
| 51 | |
| 52 | if is_provably_safe(func, &loops, &preds, index, lower, upper) { |
| 53 | to_remove.push((block.id, inst_idx)); |
| 54 | } |
| 55 | } |
| 56 | } |
| 57 | } |
| 58 | } |
| 59 | |
| 60 | if to_remove.is_empty() { |
| 61 | return false; |
| 62 | } |
| 63 | |
| 64 | // Remove in reverse order to preserve indices. |
| 65 | to_remove.sort_by_key(|entry| std::cmp::Reverse(entry.1)); |
| 66 | for (block_id, inst_idx) in to_remove { |
| 67 | func.block_mut(block_id).insts.remove(inst_idx); |
| 68 | } |
| 69 | |
| 70 | true |
| 71 | } |
| 72 | |
| 73 | /// Check if an array index is provably within [lower, upper]. |
| 74 | fn is_provably_safe( |
| 75 | func: &Function, |
| 76 | loops: &[crate::ir::walk::NaturalLoop], |
| 77 | preds: &std::collections::HashMap<BlockId, Vec<BlockId>>, |
| 78 | index: ValueId, |
| 79 | lower: ValueId, |
| 80 | upper: ValueId, |
| 81 | ) -> bool { |
| 82 | let index = strip_int_casts(func, index); |
| 83 | |
| 84 | // Case 1: constant index, constant bounds. |
| 85 | if let (Some(idx), Some(lo), Some(hi)) = ( |
| 86 | resolve_int_scalar(func, index), |
| 87 | resolve_int_scalar(func, lower), |
| 88 | resolve_int_scalar(func, upper), |
| 89 | ) { |
| 90 | return idx >= lo && idx <= hi; |
| 91 | } |
| 92 | |
| 93 | // Case 2: index is a canonical loop IV, and the loop's closed range |
| 94 | // stays within the checked bounds. |
| 95 | let Some(lo_const) = resolve_int_scalar(func, lower) else { |
| 96 | return false; |
| 97 | }; |
| 98 | let Some(hi_const) = resolve_int_scalar(func, upper) else { |
| 99 | return false; |
| 100 | }; |
| 101 | for lp in loops { |
| 102 | let Some((range_lo, range_hi)) = loop_index_range(func, lp, preds, index) else { |
| 103 | continue; |
| 104 | }; |
| 105 | if range_lo >= lo_const && range_hi <= hi_const { |
| 106 | return true; |
| 107 | } |
| 108 | } |
| 109 | |
| 110 | false |
| 111 | } |
| 112 | |
| 113 | fn loop_index_range( |
| 114 | func: &Function, |
| 115 | lp: &crate::ir::walk::NaturalLoop, |
| 116 | preds: &std::collections::HashMap<BlockId, Vec<BlockId>>, |
| 117 | index: ValueId, |
| 118 | ) -> Option<(i64, i64)> { |
| 119 | let (index, scale, offset) = loop_index_base_and_offset(func, index)?; |
| 120 | let header = func.block(lp.header); |
| 121 | let param_idx = header.params.iter().position(|param| param.id == index)?; |
| 122 | let init = loop_init_const(func, lp, preds, param_idx)?; |
| 123 | let (bound, dir) = loop_bound_const(func, lp.header, index)?; |
| 124 | let step = loop_step_const(func, lp, param_idx, index)?; |
| 125 | |
| 126 | let (range_lo, range_hi) = match dir { |
| 127 | LoopDir::Ascending if step > 0 => { |
| 128 | if init > bound { |
| 129 | return None; |
| 130 | } |
| 131 | let trip = bound.checked_sub(init)?; |
| 132 | let last = init.checked_add((trip / step).checked_mul(step)?)?; |
| 133 | (init.min(last), init.max(last)) |
| 134 | } |
| 135 | LoopDir::Descending if step < 0 => { |
| 136 | if init < bound { |
| 137 | return None; |
| 138 | } |
| 139 | let step_mag = step.checked_neg()?; |
| 140 | let trip = init.checked_sub(bound)?; |
| 141 | let last = init.checked_sub((trip / step_mag).checked_mul(step_mag)?)?; |
| 142 | (init.min(last), init.max(last)) |
| 143 | } |
| 144 | _ => return None, |
| 145 | }; |
| 146 | // Apply scale and offset: idx == scale * base + offset, with |
| 147 | // `base` ranging over [range_lo, range_hi]. Negative scale flips |
| 148 | // the interval, so take min/max after multiplying both endpoints. |
| 149 | let lo_scaled = scale.checked_mul(range_lo)?; |
| 150 | let hi_scaled = scale.checked_mul(range_hi)?; |
| 151 | let adj_lo = lo_scaled.min(hi_scaled).checked_add(offset)?; |
| 152 | let adj_hi = lo_scaled.max(hi_scaled).checked_add(offset)?; |
| 153 | Some((adj_lo, adj_hi)) |
| 154 | } |
| 155 | |
| 156 | /// Decompose `value` into a linear function of an inner SSA value: |
| 157 | /// `value == scale * base + offset`. The "base" returned is whatever |
| 158 | /// definition is left after we've stripped IAdd / ISub / IMul of |
| 159 | /// constant operands; if `base` is the loop induction variable, the |
| 160 | /// caller can then map a known IV range into a known range for |
| 161 | /// `value` itself. |
| 162 | /// |
| 163 | /// Default decomposition is `(value, 1, 0)` (i.e. base==value, no |
| 164 | /// scale, no offset). Recurses through: |
| 165 | /// * `iadd lhs, const` / `isub lhs, const` → bumps offset. |
| 166 | /// * `imul lhs, const` / `imul const, rhs` → multiplies both scale |
| 167 | /// and offset, capturing `(2*i) + 3 = 2*i + 3` and `2*(i+1) = 2*i + 2`. |
| 168 | fn loop_index_base_and_offset(func: &Function, value: ValueId) -> Option<(ValueId, i64, i64)> { |
| 169 | let value = strip_int_casts(func, value); |
| 170 | let Some(kind) = find_inst_kind(func, value) else { |
| 171 | return Some((value, 1, 0)); |
| 172 | }; |
| 173 | |
| 174 | match kind { |
| 175 | InstKind::IAdd(lhs, rhs) => { |
| 176 | if let Some((base, scale, offset)) = loop_index_base_and_offset(func, *lhs) { |
| 177 | if let Some(delta) = resolve_int_scalar(func, *rhs) { |
| 178 | return offset.checked_add(delta).map(|next| (base, scale, next)); |
| 179 | } |
| 180 | } |
| 181 | if let Some((base, scale, offset)) = loop_index_base_and_offset(func, *rhs) { |
| 182 | if let Some(delta) = resolve_int_scalar(func, *lhs) { |
| 183 | return offset.checked_add(delta).map(|next| (base, scale, next)); |
| 184 | } |
| 185 | } |
| 186 | Some((value, 1, 0)) |
| 187 | } |
| 188 | InstKind::ISub(lhs, rhs) => { |
| 189 | if let Some((base, scale, offset)) = loop_index_base_and_offset(func, *lhs) { |
| 190 | if let Some(delta) = resolve_int_scalar(func, *rhs) { |
| 191 | return offset.checked_sub(delta).map(|next| (base, scale, next)); |
| 192 | } |
| 193 | } |
| 194 | Some((value, 1, 0)) |
| 195 | } |
| 196 | InstKind::IMul(lhs, rhs) => { |
| 197 | // k * (s * base + o) = (k*s) * base + k*o |
| 198 | if let Some((base, scale, offset)) = loop_index_base_and_offset(func, *lhs) { |
| 199 | if let Some(k) = resolve_int_scalar(func, *rhs) { |
| 200 | let new_scale = scale.checked_mul(k)?; |
| 201 | let new_offset = offset.checked_mul(k)?; |
| 202 | return Some((base, new_scale, new_offset)); |
| 203 | } |
| 204 | } |
| 205 | if let Some((base, scale, offset)) = loop_index_base_and_offset(func, *rhs) { |
| 206 | if let Some(k) = resolve_int_scalar(func, *lhs) { |
| 207 | let new_scale = scale.checked_mul(k)?; |
| 208 | let new_offset = offset.checked_mul(k)?; |
| 209 | return Some((base, new_scale, new_offset)); |
| 210 | } |
| 211 | } |
| 212 | Some((value, 1, 0)) |
| 213 | } |
| 214 | _ => Some((value, 1, 0)), |
| 215 | } |
| 216 | } |
| 217 | |
| 218 | fn loop_init_const( |
| 219 | func: &Function, |
| 220 | lp: &crate::ir::walk::NaturalLoop, |
| 221 | preds: &std::collections::HashMap<BlockId, Vec<BlockId>>, |
| 222 | param_idx: usize, |
| 223 | ) -> Option<i64> { |
| 224 | let preheader = find_preheader(func, lp, preds)?; |
| 225 | match &func.block(preheader).terminator { |
| 226 | Some(Terminator::Branch(dest, args)) if *dest == lp.header && param_idx < args.len() => { |
| 227 | resolve_int_scalar(func, args[param_idx]) |
| 228 | } |
| 229 | _ => None, |
| 230 | } |
| 231 | } |
| 232 | |
| 233 | #[derive(Clone, Copy, Debug, PartialEq, Eq)] |
| 234 | enum LoopDir { |
| 235 | Ascending, |
| 236 | Descending, |
| 237 | } |
| 238 | |
| 239 | fn loop_bound_const(func: &Function, header: BlockId, index: ValueId) -> Option<(i64, LoopDir)> { |
| 240 | for inst in &func.block(header).insts { |
| 241 | let InstKind::ICmp(op, lhs, rhs) = &inst.kind else { |
| 242 | continue; |
| 243 | }; |
| 244 | match op { |
| 245 | CmpOp::Le => { |
| 246 | if *lhs == index { |
| 247 | return resolve_int_scalar(func, *rhs).map(|bound| (bound, LoopDir::Ascending)); |
| 248 | } |
| 249 | if *rhs == index { |
| 250 | return resolve_int_scalar(func, *lhs) |
| 251 | .map(|bound| (bound, LoopDir::Descending)); |
| 252 | } |
| 253 | } |
| 254 | CmpOp::Ge => { |
| 255 | if *lhs == index { |
| 256 | return resolve_int_scalar(func, *rhs) |
| 257 | .map(|bound| (bound, LoopDir::Descending)); |
| 258 | } |
| 259 | if *rhs == index { |
| 260 | return resolve_int_scalar(func, *lhs).map(|bound| (bound, LoopDir::Ascending)); |
| 261 | } |
| 262 | } |
| 263 | _ => {} |
| 264 | } |
| 265 | } |
| 266 | None |
| 267 | } |
| 268 | |
| 269 | fn loop_step_const( |
| 270 | func: &Function, |
| 271 | lp: &crate::ir::walk::NaturalLoop, |
| 272 | param_idx: usize, |
| 273 | index: ValueId, |
| 274 | ) -> Option<i64> { |
| 275 | let mut step: Option<i64> = None; |
| 276 | for &latch in &lp.latches { |
| 277 | let next = edge_arg_value(func.block(latch).terminator.as_ref()?, lp.header, param_idx)?; |
| 278 | let latch_step = update_step_const(func, index, next)?; |
| 279 | if latch_step == 0 { |
| 280 | return None; |
| 281 | } |
| 282 | match step { |
| 283 | Some(prev) if prev != latch_step => return None, |
| 284 | Some(_) => {} |
| 285 | None => step = Some(latch_step), |
| 286 | } |
| 287 | } |
| 288 | step |
| 289 | } |
| 290 | |
| 291 | fn edge_arg_value(term: &Terminator, target: BlockId, param_idx: usize) -> Option<ValueId> { |
| 292 | match term { |
| 293 | Terminator::Branch(dest, args) if *dest == target => args.get(param_idx).copied(), |
| 294 | Terminator::CondBranch { |
| 295 | true_dest, |
| 296 | true_args, |
| 297 | false_dest, |
| 298 | false_args, |
| 299 | .. |
| 300 | } => { |
| 301 | if *true_dest == target { |
| 302 | true_args.get(param_idx).copied() |
| 303 | } else if *false_dest == target { |
| 304 | false_args.get(param_idx).copied() |
| 305 | } else { |
| 306 | None |
| 307 | } |
| 308 | } |
| 309 | _ => None, |
| 310 | } |
| 311 | } |
| 312 | |
| 313 | fn update_step_const(func: &Function, index: ValueId, next: ValueId) -> Option<i64> { |
| 314 | let next = strip_int_casts(func, next); |
| 315 | if next == index { |
| 316 | return Some(0); |
| 317 | } |
| 318 | |
| 319 | let kind = find_inst_kind(func, next)?; |
| 320 | match kind { |
| 321 | InstKind::IAdd(lhs, rhs) => { |
| 322 | if *lhs == index { |
| 323 | resolve_int_scalar(func, *rhs) |
| 324 | } else if *rhs == index { |
| 325 | resolve_int_scalar(func, *lhs) |
| 326 | } else { |
| 327 | None |
| 328 | } |
| 329 | } |
| 330 | InstKind::ISub(lhs, rhs) if *lhs == index => { |
| 331 | resolve_int_scalar(func, *rhs).map(|step| -step) |
| 332 | } |
| 333 | _ => None, |
| 334 | } |
| 335 | } |
| 336 | |
| 337 | fn resolve_int_scalar(func: &Function, value: ValueId) -> Option<i64> { |
| 338 | let kind = find_inst_kind(func, value)?; |
| 339 | match kind { |
| 340 | InstKind::ConstInt(v, _) => i64::try_from(*v).ok(), |
| 341 | InstKind::IntExtend(src, _, _) | InstKind::IntTrunc(src, _) => { |
| 342 | resolve_int_scalar(func, *src) |
| 343 | } |
| 344 | _ => resolve_const_int(func, value), |
| 345 | } |
| 346 | } |
| 347 | |
| 348 | fn strip_int_casts(func: &Function, mut value: ValueId) -> ValueId { |
| 349 | loop { |
| 350 | let Some(kind) = find_inst_kind(func, value) else { |
| 351 | return value; |
| 352 | }; |
| 353 | match kind { |
| 354 | InstKind::IntExtend(src, _, _) | InstKind::IntTrunc(src, _) => value = *src, |
| 355 | _ => return value, |
| 356 | } |
| 357 | } |
| 358 | } |
| 359 | |
| 360 | fn find_inst_kind(func: &Function, value: ValueId) -> Option<&InstKind> { |
| 361 | for block in &func.blocks { |
| 362 | for inst in &block.insts { |
| 363 | if inst.id == value { |
| 364 | return Some(&inst.kind); |
| 365 | } |
| 366 | } |
| 367 | } |
| 368 | None |
| 369 | } |
| 370 | |
| 371 | #[cfg(test)] |
| 372 | mod tests { |
| 373 | use super::*; |
| 374 | use crate::ir::types::{IntWidth, IrType}; |
| 375 | use crate::opt::pass::Pass; |
| 376 | |
| 377 | #[test] |
| 378 | fn bce_no_op_without_bounds_checks() { |
| 379 | let mut m = Module::new("test".into()); |
| 380 | let mut f = Function::new("test".into(), vec![], IrType::Void); |
| 381 | f.block_mut(f.entry).terminator = Some(Terminator::Return(None)); |
| 382 | m.add_function(f); |
| 383 | let pass = Bce; |
| 384 | assert!(!pass.run(&mut m), "no CheckBounds → no elimination"); |
| 385 | } |
| 386 | |
| 387 | #[test] |
| 388 | fn bce_removes_constant_in_bounds() { |
| 389 | let mut m = Module::new("test".into()); |
| 390 | let mut f = Function::new("test".into(), vec![], IrType::Void); |
| 391 | let span = crate::lexer::Span { |
| 392 | file_id: 0, |
| 393 | start: crate::lexer::Position { line: 0, col: 0 }, |
| 394 | end: crate::lexer::Position { line: 0, col: 0 }, |
| 395 | }; |
| 396 | |
| 397 | // index = 3, lower = 1, upper = 10 → safe |
| 398 | let idx = f.next_value_id(); |
| 399 | f.register_type(idx, IrType::Int(IntWidth::I32)); |
| 400 | f.block_mut(f.entry).insts.push(Inst { |
| 401 | id: idx, |
| 402 | ty: IrType::Int(IntWidth::I32), |
| 403 | span, |
| 404 | kind: InstKind::ConstInt(3, IntWidth::I32), |
| 405 | }); |
| 406 | let lo = f.next_value_id(); |
| 407 | f.register_type(lo, IrType::Int(IntWidth::I32)); |
| 408 | f.block_mut(f.entry).insts.push(Inst { |
| 409 | id: lo, |
| 410 | ty: IrType::Int(IntWidth::I32), |
| 411 | span, |
| 412 | kind: InstKind::ConstInt(1, IntWidth::I32), |
| 413 | }); |
| 414 | let hi = f.next_value_id(); |
| 415 | f.register_type(hi, IrType::Int(IntWidth::I32)); |
| 416 | f.block_mut(f.entry).insts.push(Inst { |
| 417 | id: hi, |
| 418 | ty: IrType::Int(IntWidth::I32), |
| 419 | span, |
| 420 | kind: InstKind::ConstInt(10, IntWidth::I32), |
| 421 | }); |
| 422 | let check = f.next_value_id(); |
| 423 | f.register_type(check, IrType::Void); |
| 424 | f.block_mut(f.entry).insts.push(Inst { |
| 425 | id: check, |
| 426 | ty: IrType::Void, |
| 427 | span, |
| 428 | kind: InstKind::RuntimeCall(RuntimeFunc::CheckBounds, vec![idx, lo, hi]), |
| 429 | }); |
| 430 | f.block_mut(f.entry).terminator = Some(Terminator::Return(None)); |
| 431 | m.add_function(f); |
| 432 | |
| 433 | let pass = Bce; |
| 434 | let changed = pass.run(&mut m); |
| 435 | assert!(changed, "constant 3 in [1,10] should be eliminated"); |
| 436 | |
| 437 | // Verify the CheckBounds call was removed. |
| 438 | let has_check = m.functions[0].blocks[0] |
| 439 | .insts |
| 440 | .iter() |
| 441 | .any(|i| matches!(i.kind, InstKind::RuntimeCall(RuntimeFunc::CheckBounds, _))); |
| 442 | assert!(!has_check, "CheckBounds should be removed"); |
| 443 | } |
| 444 | |
| 445 | #[test] |
| 446 | fn bce_removes_canonical_loop_iv_check() { |
| 447 | let mut m = Module::new("test".into()); |
| 448 | let mut f = Function::new("test".into(), vec![], IrType::Void); |
| 449 | let span = crate::lexer::Span { |
| 450 | file_id: 0, |
| 451 | start: crate::lexer::Position { line: 0, col: 0 }, |
| 452 | end: crate::lexer::Position { line: 0, col: 0 }, |
| 453 | }; |
| 454 | |
| 455 | let header = f.create_block("header"); |
| 456 | let body = f.create_block("body"); |
| 457 | let exit = f.create_block("exit"); |
| 458 | |
| 459 | let init = f.next_value_id(); |
| 460 | f.register_type(init, IrType::Int(IntWidth::I32)); |
| 461 | f.block_mut(f.entry).insts.push(Inst { |
| 462 | id: init, |
| 463 | ty: IrType::Int(IntWidth::I32), |
| 464 | span, |
| 465 | kind: InstKind::ConstInt(1, IntWidth::I32), |
| 466 | }); |
| 467 | let zero = f.next_value_id(); |
| 468 | f.register_type(zero, IrType::Int(IntWidth::I32)); |
| 469 | f.block_mut(f.entry).insts.push(Inst { |
| 470 | id: zero, |
| 471 | ty: IrType::Int(IntWidth::I32), |
| 472 | span, |
| 473 | kind: InstKind::ConstInt(0, IntWidth::I32), |
| 474 | }); |
| 475 | f.block_mut(f.entry).terminator = Some(Terminator::Branch(header, vec![init, zero])); |
| 476 | |
| 477 | let iv = f.next_value_id(); |
| 478 | f.register_type(iv, IrType::Int(IntWidth::I32)); |
| 479 | let sum = f.next_value_id(); |
| 480 | f.register_type(sum, IrType::Int(IntWidth::I32)); |
| 481 | f.block_mut(header).params.push(BlockParam { |
| 482 | id: iv, |
| 483 | ty: IrType::Int(IntWidth::I32), |
| 484 | }); |
| 485 | f.block_mut(header).params.push(BlockParam { |
| 486 | id: sum, |
| 487 | ty: IrType::Int(IntWidth::I32), |
| 488 | }); |
| 489 | |
| 490 | let bound = f.next_value_id(); |
| 491 | f.register_type(bound, IrType::Int(IntWidth::I32)); |
| 492 | f.block_mut(header).insts.push(Inst { |
| 493 | id: bound, |
| 494 | ty: IrType::Int(IntWidth::I32), |
| 495 | span, |
| 496 | kind: InstKind::ConstInt(4, IntWidth::I32), |
| 497 | }); |
| 498 | let cond = f.next_value_id(); |
| 499 | f.register_type(cond, IrType::Bool); |
| 500 | f.block_mut(header).insts.push(Inst { |
| 501 | id: cond, |
| 502 | ty: IrType::Bool, |
| 503 | span, |
| 504 | kind: InstKind::ICmp(CmpOp::Le, iv, bound), |
| 505 | }); |
| 506 | f.block_mut(header).terminator = Some(Terminator::CondBranch { |
| 507 | cond, |
| 508 | true_dest: body, |
| 509 | true_args: vec![], |
| 510 | false_dest: exit, |
| 511 | false_args: vec![], |
| 512 | }); |
| 513 | |
| 514 | let iv64 = f.next_value_id(); |
| 515 | f.register_type(iv64, IrType::Int(IntWidth::I64)); |
| 516 | f.block_mut(body).insts.push(Inst { |
| 517 | id: iv64, |
| 518 | ty: IrType::Int(IntWidth::I64), |
| 519 | span, |
| 520 | kind: InstKind::IntExtend(iv, IntWidth::I64, true), |
| 521 | }); |
| 522 | let lo = f.next_value_id(); |
| 523 | f.register_type(lo, IrType::Int(IntWidth::I64)); |
| 524 | f.block_mut(body).insts.push(Inst { |
| 525 | id: lo, |
| 526 | ty: IrType::Int(IntWidth::I64), |
| 527 | span, |
| 528 | kind: InstKind::ConstInt(1, IntWidth::I64), |
| 529 | }); |
| 530 | let hi = f.next_value_id(); |
| 531 | f.register_type(hi, IrType::Int(IntWidth::I64)); |
| 532 | f.block_mut(body).insts.push(Inst { |
| 533 | id: hi, |
| 534 | ty: IrType::Int(IntWidth::I64), |
| 535 | span, |
| 536 | kind: InstKind::ConstInt(4, IntWidth::I64), |
| 537 | }); |
| 538 | let check = f.next_value_id(); |
| 539 | f.register_type(check, IrType::Void); |
| 540 | f.block_mut(body).insts.push(Inst { |
| 541 | id: check, |
| 542 | ty: IrType::Void, |
| 543 | span, |
| 544 | kind: InstKind::RuntimeCall(RuntimeFunc::CheckBounds, vec![iv64, lo, hi]), |
| 545 | }); |
| 546 | let step = f.next_value_id(); |
| 547 | f.register_type(step, IrType::Int(IntWidth::I32)); |
| 548 | f.block_mut(body).insts.push(Inst { |
| 549 | id: step, |
| 550 | ty: IrType::Int(IntWidth::I32), |
| 551 | span, |
| 552 | kind: InstKind::ConstInt(1, IntWidth::I32), |
| 553 | }); |
| 554 | let next_iv = f.next_value_id(); |
| 555 | f.register_type(next_iv, IrType::Int(IntWidth::I32)); |
| 556 | f.block_mut(body).insts.push(Inst { |
| 557 | id: next_iv, |
| 558 | ty: IrType::Int(IntWidth::I32), |
| 559 | span, |
| 560 | kind: InstKind::IAdd(iv, step), |
| 561 | }); |
| 562 | let next_sum = f.next_value_id(); |
| 563 | f.register_type(next_sum, IrType::Int(IntWidth::I32)); |
| 564 | f.block_mut(body).insts.push(Inst { |
| 565 | id: next_sum, |
| 566 | ty: IrType::Int(IntWidth::I32), |
| 567 | span, |
| 568 | kind: InstKind::IAdd(sum, step), |
| 569 | }); |
| 570 | f.block_mut(body).terminator = Some(Terminator::Branch(header, vec![next_iv, next_sum])); |
| 571 | f.block_mut(exit).terminator = Some(Terminator::Return(None)); |
| 572 | m.add_function(f); |
| 573 | |
| 574 | let pass = Bce; |
| 575 | assert!( |
| 576 | pass.run(&mut m), |
| 577 | "canonical counted-loop bounds check should be removed" |
| 578 | ); |
| 579 | let has_check = m.functions[0].block(body).insts.iter().any(|inst| { |
| 580 | matches!( |
| 581 | inst.kind, |
| 582 | InstKind::RuntimeCall(RuntimeFunc::CheckBounds, _) |
| 583 | ) |
| 584 | }); |
| 585 | assert!(!has_check, "loop body should no longer contain CheckBounds"); |
| 586 | } |
| 587 | |
| 588 | #[test] |
| 589 | fn bce_keeps_loop_check_when_bounds_are_tighter_than_trip_range() { |
| 590 | let mut m = Module::new("test".into()); |
| 591 | let mut f = Function::new("test".into(), vec![], IrType::Void); |
| 592 | let span = crate::lexer::Span { |
| 593 | file_id: 0, |
| 594 | start: crate::lexer::Position { line: 0, col: 0 }, |
| 595 | end: crate::lexer::Position { line: 0, col: 0 }, |
| 596 | }; |
| 597 | |
| 598 | let header = f.create_block("header"); |
| 599 | let body = f.create_block("body"); |
| 600 | let exit = f.create_block("exit"); |
| 601 | |
| 602 | let init = f.next_value_id(); |
| 603 | f.register_type(init, IrType::Int(IntWidth::I32)); |
| 604 | f.block_mut(f.entry).insts.push(Inst { |
| 605 | id: init, |
| 606 | ty: IrType::Int(IntWidth::I32), |
| 607 | span, |
| 608 | kind: InstKind::ConstInt(1, IntWidth::I32), |
| 609 | }); |
| 610 | let zero = f.next_value_id(); |
| 611 | f.register_type(zero, IrType::Int(IntWidth::I32)); |
| 612 | f.block_mut(f.entry).insts.push(Inst { |
| 613 | id: zero, |
| 614 | ty: IrType::Int(IntWidth::I32), |
| 615 | span, |
| 616 | kind: InstKind::ConstInt(0, IntWidth::I32), |
| 617 | }); |
| 618 | f.block_mut(f.entry).terminator = Some(Terminator::Branch(header, vec![init, zero])); |
| 619 | |
| 620 | let iv = f.next_value_id(); |
| 621 | f.register_type(iv, IrType::Int(IntWidth::I32)); |
| 622 | let sum = f.next_value_id(); |
| 623 | f.register_type(sum, IrType::Int(IntWidth::I32)); |
| 624 | f.block_mut(header).params.push(BlockParam { |
| 625 | id: iv, |
| 626 | ty: IrType::Int(IntWidth::I32), |
| 627 | }); |
| 628 | f.block_mut(header).params.push(BlockParam { |
| 629 | id: sum, |
| 630 | ty: IrType::Int(IntWidth::I32), |
| 631 | }); |
| 632 | |
| 633 | let bound = f.next_value_id(); |
| 634 | f.register_type(bound, IrType::Int(IntWidth::I32)); |
| 635 | f.block_mut(header).insts.push(Inst { |
| 636 | id: bound, |
| 637 | ty: IrType::Int(IntWidth::I32), |
| 638 | span, |
| 639 | kind: InstKind::ConstInt(4, IntWidth::I32), |
| 640 | }); |
| 641 | let cond = f.next_value_id(); |
| 642 | f.register_type(cond, IrType::Bool); |
| 643 | f.block_mut(header).insts.push(Inst { |
| 644 | id: cond, |
| 645 | ty: IrType::Bool, |
| 646 | span, |
| 647 | kind: InstKind::ICmp(CmpOp::Le, iv, bound), |
| 648 | }); |
| 649 | f.block_mut(header).terminator = Some(Terminator::CondBranch { |
| 650 | cond, |
| 651 | true_dest: body, |
| 652 | true_args: vec![], |
| 653 | false_dest: exit, |
| 654 | false_args: vec![], |
| 655 | }); |
| 656 | |
| 657 | let iv64 = f.next_value_id(); |
| 658 | f.register_type(iv64, IrType::Int(IntWidth::I64)); |
| 659 | f.block_mut(body).insts.push(Inst { |
| 660 | id: iv64, |
| 661 | ty: IrType::Int(IntWidth::I64), |
| 662 | span, |
| 663 | kind: InstKind::IntExtend(iv, IntWidth::I64, true), |
| 664 | }); |
| 665 | let lo = f.next_value_id(); |
| 666 | f.register_type(lo, IrType::Int(IntWidth::I64)); |
| 667 | f.block_mut(body).insts.push(Inst { |
| 668 | id: lo, |
| 669 | ty: IrType::Int(IntWidth::I64), |
| 670 | span, |
| 671 | kind: InstKind::ConstInt(1, IntWidth::I64), |
| 672 | }); |
| 673 | let hi = f.next_value_id(); |
| 674 | f.register_type(hi, IrType::Int(IntWidth::I64)); |
| 675 | f.block_mut(body).insts.push(Inst { |
| 676 | id: hi, |
| 677 | ty: IrType::Int(IntWidth::I64), |
| 678 | span, |
| 679 | kind: InstKind::ConstInt(3, IntWidth::I64), |
| 680 | }); |
| 681 | let check = f.next_value_id(); |
| 682 | f.register_type(check, IrType::Void); |
| 683 | f.block_mut(body).insts.push(Inst { |
| 684 | id: check, |
| 685 | ty: IrType::Void, |
| 686 | span, |
| 687 | kind: InstKind::RuntimeCall(RuntimeFunc::CheckBounds, vec![iv64, lo, hi]), |
| 688 | }); |
| 689 | let step = f.next_value_id(); |
| 690 | f.register_type(step, IrType::Int(IntWidth::I32)); |
| 691 | f.block_mut(body).insts.push(Inst { |
| 692 | id: step, |
| 693 | ty: IrType::Int(IntWidth::I32), |
| 694 | span, |
| 695 | kind: InstKind::ConstInt(1, IntWidth::I32), |
| 696 | }); |
| 697 | let next_iv = f.next_value_id(); |
| 698 | f.register_type(next_iv, IrType::Int(IntWidth::I32)); |
| 699 | f.block_mut(body).insts.push(Inst { |
| 700 | id: next_iv, |
| 701 | ty: IrType::Int(IntWidth::I32), |
| 702 | span, |
| 703 | kind: InstKind::IAdd(iv, step), |
| 704 | }); |
| 705 | let next_sum = f.next_value_id(); |
| 706 | f.register_type(next_sum, IrType::Int(IntWidth::I32)); |
| 707 | f.block_mut(body).insts.push(Inst { |
| 708 | id: next_sum, |
| 709 | ty: IrType::Int(IntWidth::I32), |
| 710 | span, |
| 711 | kind: InstKind::IAdd(sum, step), |
| 712 | }); |
| 713 | f.block_mut(body).terminator = Some(Terminator::Branch(header, vec![next_iv, next_sum])); |
| 714 | f.block_mut(exit).terminator = Some(Terminator::Return(None)); |
| 715 | m.add_function(f); |
| 716 | |
| 717 | let pass = Bce; |
| 718 | assert!( |
| 719 | !pass.run(&mut m), |
| 720 | "loop trip range 1..4 exceeds checked upper bound 3, so CheckBounds must remain" |
| 721 | ); |
| 722 | } |
| 723 | |
| 724 | #[test] |
| 725 | fn bce_removes_loop_iv_plus_constant_check() { |
| 726 | let mut m = Module::new("test".into()); |
| 727 | let mut f = Function::new("test".into(), vec![], IrType::Void); |
| 728 | let span = crate::lexer::Span { |
| 729 | file_id: 0, |
| 730 | start: crate::lexer::Position { line: 0, col: 0 }, |
| 731 | end: crate::lexer::Position { line: 0, col: 0 }, |
| 732 | }; |
| 733 | |
| 734 | let header = f.create_block("header"); |
| 735 | let body = f.create_block("body"); |
| 736 | let exit = f.create_block("exit"); |
| 737 | |
| 738 | let init = f.next_value_id(); |
| 739 | f.register_type(init, IrType::Int(IntWidth::I32)); |
| 740 | f.block_mut(f.entry).insts.push(Inst { |
| 741 | id: init, |
| 742 | ty: IrType::Int(IntWidth::I32), |
| 743 | span, |
| 744 | kind: InstKind::ConstInt(2, IntWidth::I32), |
| 745 | }); |
| 746 | f.block_mut(f.entry).terminator = Some(Terminator::Branch(header, vec![init])); |
| 747 | |
| 748 | let iv = f.next_value_id(); |
| 749 | f.register_type(iv, IrType::Int(IntWidth::I32)); |
| 750 | f.block_mut(header).params.push(BlockParam { |
| 751 | id: iv, |
| 752 | ty: IrType::Int(IntWidth::I32), |
| 753 | }); |
| 754 | |
| 755 | let bound = f.next_value_id(); |
| 756 | f.register_type(bound, IrType::Int(IntWidth::I32)); |
| 757 | f.block_mut(header).insts.push(Inst { |
| 758 | id: bound, |
| 759 | ty: IrType::Int(IntWidth::I32), |
| 760 | span, |
| 761 | kind: InstKind::ConstInt(7, IntWidth::I32), |
| 762 | }); |
| 763 | let cond = f.next_value_id(); |
| 764 | f.register_type(cond, IrType::Bool); |
| 765 | f.block_mut(header).insts.push(Inst { |
| 766 | id: cond, |
| 767 | ty: IrType::Bool, |
| 768 | span, |
| 769 | kind: InstKind::ICmp(CmpOp::Le, iv, bound), |
| 770 | }); |
| 771 | f.block_mut(header).terminator = Some(Terminator::CondBranch { |
| 772 | cond, |
| 773 | true_dest: body, |
| 774 | true_args: vec![], |
| 775 | false_dest: exit, |
| 776 | false_args: vec![], |
| 777 | }); |
| 778 | |
| 779 | let one = f.next_value_id(); |
| 780 | f.register_type(one, IrType::Int(IntWidth::I32)); |
| 781 | f.block_mut(body).insts.push(Inst { |
| 782 | id: one, |
| 783 | ty: IrType::Int(IntWidth::I32), |
| 784 | span, |
| 785 | kind: InstKind::ConstInt(1, IntWidth::I32), |
| 786 | }); |
| 787 | let plus = f.next_value_id(); |
| 788 | f.register_type(plus, IrType::Int(IntWidth::I32)); |
| 789 | f.block_mut(body).insts.push(Inst { |
| 790 | id: plus, |
| 791 | ty: IrType::Int(IntWidth::I32), |
| 792 | span, |
| 793 | kind: InstKind::IAdd(iv, one), |
| 794 | }); |
| 795 | let plus64 = f.next_value_id(); |
| 796 | f.register_type(plus64, IrType::Int(IntWidth::I64)); |
| 797 | f.block_mut(body).insts.push(Inst { |
| 798 | id: plus64, |
| 799 | ty: IrType::Int(IntWidth::I64), |
| 800 | span, |
| 801 | kind: InstKind::IntExtend(plus, IntWidth::I64, true), |
| 802 | }); |
| 803 | let lo = f.next_value_id(); |
| 804 | f.register_type(lo, IrType::Int(IntWidth::I64)); |
| 805 | f.block_mut(body).insts.push(Inst { |
| 806 | id: lo, |
| 807 | ty: IrType::Int(IntWidth::I64), |
| 808 | span, |
| 809 | kind: InstKind::ConstInt(1, IntWidth::I64), |
| 810 | }); |
| 811 | let hi = f.next_value_id(); |
| 812 | f.register_type(hi, IrType::Int(IntWidth::I64)); |
| 813 | f.block_mut(body).insts.push(Inst { |
| 814 | id: hi, |
| 815 | ty: IrType::Int(IntWidth::I64), |
| 816 | span, |
| 817 | kind: InstKind::ConstInt(8, IntWidth::I64), |
| 818 | }); |
| 819 | let check = f.next_value_id(); |
| 820 | f.register_type(check, IrType::Void); |
| 821 | f.block_mut(body).insts.push(Inst { |
| 822 | id: check, |
| 823 | ty: IrType::Void, |
| 824 | span, |
| 825 | kind: InstKind::RuntimeCall(RuntimeFunc::CheckBounds, vec![plus64, lo, hi]), |
| 826 | }); |
| 827 | let next_iv = f.next_value_id(); |
| 828 | f.register_type(next_iv, IrType::Int(IntWidth::I32)); |
| 829 | f.block_mut(body).insts.push(Inst { |
| 830 | id: next_iv, |
| 831 | ty: IrType::Int(IntWidth::I32), |
| 832 | span, |
| 833 | kind: InstKind::IAdd(iv, one), |
| 834 | }); |
| 835 | f.block_mut(body).terminator = Some(Terminator::Branch(header, vec![next_iv])); |
| 836 | f.block_mut(exit).terminator = Some(Terminator::Return(None)); |
| 837 | m.add_function(f); |
| 838 | |
| 839 | let pass = Bce; |
| 840 | assert!( |
| 841 | pass.run(&mut m), |
| 842 | "iv+1 check should be removed for trip range 2..7 and checked bounds 1..8" |
| 843 | ); |
| 844 | let has_check = m.functions[0].block(body).insts.iter().any(|inst| { |
| 845 | matches!( |
| 846 | inst.kind, |
| 847 | InstKind::RuntimeCall(RuntimeFunc::CheckBounds, _) |
| 848 | ) |
| 849 | }); |
| 850 | assert!(!has_check, "loop body should no longer contain CheckBounds"); |
| 851 | } |
| 852 | |
| 853 | #[test] |
| 854 | fn bce_removes_loop_iv_minus_constant_check() { |
| 855 | let mut m = Module::new("test".into()); |
| 856 | let mut f = Function::new("test".into(), vec![], IrType::Void); |
| 857 | let span = crate::lexer::Span { |
| 858 | file_id: 0, |
| 859 | start: crate::lexer::Position { line: 0, col: 0 }, |
| 860 | end: crate::lexer::Position { line: 0, col: 0 }, |
| 861 | }; |
| 862 | |
| 863 | let header = f.create_block("header"); |
| 864 | let body = f.create_block("body"); |
| 865 | let exit = f.create_block("exit"); |
| 866 | |
| 867 | let init = f.next_value_id(); |
| 868 | f.register_type(init, IrType::Int(IntWidth::I32)); |
| 869 | f.block_mut(f.entry).insts.push(Inst { |
| 870 | id: init, |
| 871 | ty: IrType::Int(IntWidth::I32), |
| 872 | span, |
| 873 | kind: InstKind::ConstInt(2, IntWidth::I32), |
| 874 | }); |
| 875 | f.block_mut(f.entry).terminator = Some(Terminator::Branch(header, vec![init])); |
| 876 | |
| 877 | let iv = f.next_value_id(); |
| 878 | f.register_type(iv, IrType::Int(IntWidth::I32)); |
| 879 | f.block_mut(header).params.push(BlockParam { |
| 880 | id: iv, |
| 881 | ty: IrType::Int(IntWidth::I32), |
| 882 | }); |
| 883 | |
| 884 | let bound = f.next_value_id(); |
| 885 | f.register_type(bound, IrType::Int(IntWidth::I32)); |
| 886 | f.block_mut(header).insts.push(Inst { |
| 887 | id: bound, |
| 888 | ty: IrType::Int(IntWidth::I32), |
| 889 | span, |
| 890 | kind: InstKind::ConstInt(7, IntWidth::I32), |
| 891 | }); |
| 892 | let cond = f.next_value_id(); |
| 893 | f.register_type(cond, IrType::Bool); |
| 894 | f.block_mut(header).insts.push(Inst { |
| 895 | id: cond, |
| 896 | ty: IrType::Bool, |
| 897 | span, |
| 898 | kind: InstKind::ICmp(CmpOp::Le, iv, bound), |
| 899 | }); |
| 900 | f.block_mut(header).terminator = Some(Terminator::CondBranch { |
| 901 | cond, |
| 902 | true_dest: body, |
| 903 | true_args: vec![], |
| 904 | false_dest: exit, |
| 905 | false_args: vec![], |
| 906 | }); |
| 907 | |
| 908 | let one = f.next_value_id(); |
| 909 | f.register_type(one, IrType::Int(IntWidth::I32)); |
| 910 | f.block_mut(body).insts.push(Inst { |
| 911 | id: one, |
| 912 | ty: IrType::Int(IntWidth::I32), |
| 913 | span, |
| 914 | kind: InstKind::ConstInt(1, IntWidth::I32), |
| 915 | }); |
| 916 | let minus = f.next_value_id(); |
| 917 | f.register_type(minus, IrType::Int(IntWidth::I32)); |
| 918 | f.block_mut(body).insts.push(Inst { |
| 919 | id: minus, |
| 920 | ty: IrType::Int(IntWidth::I32), |
| 921 | span, |
| 922 | kind: InstKind::ISub(iv, one), |
| 923 | }); |
| 924 | let minus64 = f.next_value_id(); |
| 925 | f.register_type(minus64, IrType::Int(IntWidth::I64)); |
| 926 | f.block_mut(body).insts.push(Inst { |
| 927 | id: minus64, |
| 928 | ty: IrType::Int(IntWidth::I64), |
| 929 | span, |
| 930 | kind: InstKind::IntExtend(minus, IntWidth::I64, true), |
| 931 | }); |
| 932 | let lo = f.next_value_id(); |
| 933 | f.register_type(lo, IrType::Int(IntWidth::I64)); |
| 934 | f.block_mut(body).insts.push(Inst { |
| 935 | id: lo, |
| 936 | ty: IrType::Int(IntWidth::I64), |
| 937 | span, |
| 938 | kind: InstKind::ConstInt(1, IntWidth::I64), |
| 939 | }); |
| 940 | let hi = f.next_value_id(); |
| 941 | f.register_type(hi, IrType::Int(IntWidth::I64)); |
| 942 | f.block_mut(body).insts.push(Inst { |
| 943 | id: hi, |
| 944 | ty: IrType::Int(IntWidth::I64), |
| 945 | span, |
| 946 | kind: InstKind::ConstInt(8, IntWidth::I64), |
| 947 | }); |
| 948 | let check = f.next_value_id(); |
| 949 | f.register_type(check, IrType::Void); |
| 950 | f.block_mut(body).insts.push(Inst { |
| 951 | id: check, |
| 952 | ty: IrType::Void, |
| 953 | span, |
| 954 | kind: InstKind::RuntimeCall(RuntimeFunc::CheckBounds, vec![minus64, lo, hi]), |
| 955 | }); |
| 956 | let next_iv = f.next_value_id(); |
| 957 | f.register_type(next_iv, IrType::Int(IntWidth::I32)); |
| 958 | f.block_mut(body).insts.push(Inst { |
| 959 | id: next_iv, |
| 960 | ty: IrType::Int(IntWidth::I32), |
| 961 | span, |
| 962 | kind: InstKind::IAdd(iv, one), |
| 963 | }); |
| 964 | f.block_mut(body).terminator = Some(Terminator::Branch(header, vec![next_iv])); |
| 965 | f.block_mut(exit).terminator = Some(Terminator::Return(None)); |
| 966 | m.add_function(f); |
| 967 | |
| 968 | let pass = Bce; |
| 969 | assert!( |
| 970 | pass.run(&mut m), |
| 971 | "iv-1 check should be removed for trip range 2..7 and checked bounds 1..8" |
| 972 | ); |
| 973 | let has_check = m.functions[0].block(body).insts.iter().any(|inst| { |
| 974 | matches!( |
| 975 | inst.kind, |
| 976 | InstKind::RuntimeCall(RuntimeFunc::CheckBounds, _) |
| 977 | ) |
| 978 | }); |
| 979 | assert!(!has_check, "loop body should no longer contain CheckBounds"); |
| 980 | } |
| 981 | |
| 982 | #[test] |
| 983 | fn bce_keeps_loop_iv_plus_constant_check_when_offset_exceeds_upper_bound() { |
| 984 | let mut m = Module::new("test".into()); |
| 985 | let mut f = Function::new("test".into(), vec![], IrType::Void); |
| 986 | let span = crate::lexer::Span { |
| 987 | file_id: 0, |
| 988 | start: crate::lexer::Position { line: 0, col: 0 }, |
| 989 | end: crate::lexer::Position { line: 0, col: 0 }, |
| 990 | }; |
| 991 | |
| 992 | let header = f.create_block("header"); |
| 993 | let body = f.create_block("body"); |
| 994 | let exit = f.create_block("exit"); |
| 995 | |
| 996 | let init = f.next_value_id(); |
| 997 | f.register_type(init, IrType::Int(IntWidth::I32)); |
| 998 | f.block_mut(f.entry).insts.push(Inst { |
| 999 | id: init, |
| 1000 | ty: IrType::Int(IntWidth::I32), |
| 1001 | span, |
| 1002 | kind: InstKind::ConstInt(2, IntWidth::I32), |
| 1003 | }); |
| 1004 | f.block_mut(f.entry).terminator = Some(Terminator::Branch(header, vec![init])); |
| 1005 | |
| 1006 | let iv = f.next_value_id(); |
| 1007 | f.register_type(iv, IrType::Int(IntWidth::I32)); |
| 1008 | f.block_mut(header).params.push(BlockParam { |
| 1009 | id: iv, |
| 1010 | ty: IrType::Int(IntWidth::I32), |
| 1011 | }); |
| 1012 | |
| 1013 | let bound = f.next_value_id(); |
| 1014 | f.register_type(bound, IrType::Int(IntWidth::I32)); |
| 1015 | f.block_mut(header).insts.push(Inst { |
| 1016 | id: bound, |
| 1017 | ty: IrType::Int(IntWidth::I32), |
| 1018 | span, |
| 1019 | kind: InstKind::ConstInt(7, IntWidth::I32), |
| 1020 | }); |
| 1021 | let cond = f.next_value_id(); |
| 1022 | f.register_type(cond, IrType::Bool); |
| 1023 | f.block_mut(header).insts.push(Inst { |
| 1024 | id: cond, |
| 1025 | ty: IrType::Bool, |
| 1026 | span, |
| 1027 | kind: InstKind::ICmp(CmpOp::Le, iv, bound), |
| 1028 | }); |
| 1029 | f.block_mut(header).terminator = Some(Terminator::CondBranch { |
| 1030 | cond, |
| 1031 | true_dest: body, |
| 1032 | true_args: vec![], |
| 1033 | false_dest: exit, |
| 1034 | false_args: vec![], |
| 1035 | }); |
| 1036 | |
| 1037 | let two = f.next_value_id(); |
| 1038 | f.register_type(two, IrType::Int(IntWidth::I32)); |
| 1039 | f.block_mut(body).insts.push(Inst { |
| 1040 | id: two, |
| 1041 | ty: IrType::Int(IntWidth::I32), |
| 1042 | span, |
| 1043 | kind: InstKind::ConstInt(2, IntWidth::I32), |
| 1044 | }); |
| 1045 | let plus = f.next_value_id(); |
| 1046 | f.register_type(plus, IrType::Int(IntWidth::I32)); |
| 1047 | f.block_mut(body).insts.push(Inst { |
| 1048 | id: plus, |
| 1049 | ty: IrType::Int(IntWidth::I32), |
| 1050 | span, |
| 1051 | kind: InstKind::IAdd(iv, two), |
| 1052 | }); |
| 1053 | let plus64 = f.next_value_id(); |
| 1054 | f.register_type(plus64, IrType::Int(IntWidth::I64)); |
| 1055 | f.block_mut(body).insts.push(Inst { |
| 1056 | id: plus64, |
| 1057 | ty: IrType::Int(IntWidth::I64), |
| 1058 | span, |
| 1059 | kind: InstKind::IntExtend(plus, IntWidth::I64, true), |
| 1060 | }); |
| 1061 | let lo = f.next_value_id(); |
| 1062 | f.register_type(lo, IrType::Int(IntWidth::I64)); |
| 1063 | f.block_mut(body).insts.push(Inst { |
| 1064 | id: lo, |
| 1065 | ty: IrType::Int(IntWidth::I64), |
| 1066 | span, |
| 1067 | kind: InstKind::ConstInt(1, IntWidth::I64), |
| 1068 | }); |
| 1069 | let hi = f.next_value_id(); |
| 1070 | f.register_type(hi, IrType::Int(IntWidth::I64)); |
| 1071 | f.block_mut(body).insts.push(Inst { |
| 1072 | id: hi, |
| 1073 | ty: IrType::Int(IntWidth::I64), |
| 1074 | span, |
| 1075 | kind: InstKind::ConstInt(8, IntWidth::I64), |
| 1076 | }); |
| 1077 | let check = f.next_value_id(); |
| 1078 | f.register_type(check, IrType::Void); |
| 1079 | f.block_mut(body).insts.push(Inst { |
| 1080 | id: check, |
| 1081 | ty: IrType::Void, |
| 1082 | span, |
| 1083 | kind: InstKind::RuntimeCall(RuntimeFunc::CheckBounds, vec![plus64, lo, hi]), |
| 1084 | }); |
| 1085 | let one = f.next_value_id(); |
| 1086 | f.register_type(one, IrType::Int(IntWidth::I32)); |
| 1087 | f.block_mut(body).insts.push(Inst { |
| 1088 | id: one, |
| 1089 | ty: IrType::Int(IntWidth::I32), |
| 1090 | span, |
| 1091 | kind: InstKind::ConstInt(1, IntWidth::I32), |
| 1092 | }); |
| 1093 | let next_iv = f.next_value_id(); |
| 1094 | f.register_type(next_iv, IrType::Int(IntWidth::I32)); |
| 1095 | f.block_mut(body).insts.push(Inst { |
| 1096 | id: next_iv, |
| 1097 | ty: IrType::Int(IntWidth::I32), |
| 1098 | span, |
| 1099 | kind: InstKind::IAdd(iv, one), |
| 1100 | }); |
| 1101 | f.block_mut(body).terminator = Some(Terminator::Branch(header, vec![next_iv])); |
| 1102 | f.block_mut(exit).terminator = Some(Terminator::Return(None)); |
| 1103 | m.add_function(f); |
| 1104 | |
| 1105 | let pass = Bce; |
| 1106 | assert!( |
| 1107 | !pass.run(&mut m), |
| 1108 | "iv+2 check must remain when trip range 2..7 would access 9 beyond checked upper bound 8" |
| 1109 | ); |
| 1110 | } |
| 1111 | |
| 1112 | #[test] |
| 1113 | fn bce_removes_loop_iv_plus_constant_check_with_large_step() { |
| 1114 | let mut m = Module::new("test".into()); |
| 1115 | let mut f = Function::new("test".into(), vec![], IrType::Void); |
| 1116 | let span = crate::lexer::Span { |
| 1117 | file_id: 0, |
| 1118 | start: crate::lexer::Position { line: 0, col: 0 }, |
| 1119 | end: crate::lexer::Position { line: 0, col: 0 }, |
| 1120 | }; |
| 1121 | |
| 1122 | let header = f.create_block("header"); |
| 1123 | let body = f.create_block("body"); |
| 1124 | let exit = f.create_block("exit"); |
| 1125 | |
| 1126 | let init = f.next_value_id(); |
| 1127 | f.register_type(init, IrType::Int(IntWidth::I32)); |
| 1128 | f.block_mut(f.entry).insts.push(Inst { |
| 1129 | id: init, |
| 1130 | ty: IrType::Int(IntWidth::I32), |
| 1131 | span, |
| 1132 | kind: InstKind::ConstInt(5, IntWidth::I32), |
| 1133 | }); |
| 1134 | f.block_mut(f.entry).terminator = Some(Terminator::Branch(header, vec![init])); |
| 1135 | |
| 1136 | let iv = f.next_value_id(); |
| 1137 | f.register_type(iv, IrType::Int(IntWidth::I32)); |
| 1138 | f.block_mut(header).params.push(BlockParam { |
| 1139 | id: iv, |
| 1140 | ty: IrType::Int(IntWidth::I32), |
| 1141 | }); |
| 1142 | |
| 1143 | let bound = f.next_value_id(); |
| 1144 | f.register_type(bound, IrType::Int(IntWidth::I32)); |
| 1145 | f.block_mut(header).insts.push(Inst { |
| 1146 | id: bound, |
| 1147 | ty: IrType::Int(IntWidth::I32), |
| 1148 | span, |
| 1149 | kind: InstKind::ConstInt(10, IntWidth::I32), |
| 1150 | }); |
| 1151 | let cond = f.next_value_id(); |
| 1152 | f.register_type(cond, IrType::Bool); |
| 1153 | f.block_mut(header).insts.push(Inst { |
| 1154 | id: cond, |
| 1155 | ty: IrType::Bool, |
| 1156 | span, |
| 1157 | kind: InstKind::ICmp(CmpOp::Le, iv, bound), |
| 1158 | }); |
| 1159 | f.block_mut(header).terminator = Some(Terminator::CondBranch { |
| 1160 | cond, |
| 1161 | true_dest: body, |
| 1162 | true_args: vec![], |
| 1163 | false_dest: exit, |
| 1164 | false_args: vec![], |
| 1165 | }); |
| 1166 | |
| 1167 | let five = f.next_value_id(); |
| 1168 | f.register_type(five, IrType::Int(IntWidth::I32)); |
| 1169 | f.block_mut(body).insts.push(Inst { |
| 1170 | id: five, |
| 1171 | ty: IrType::Int(IntWidth::I32), |
| 1172 | span, |
| 1173 | kind: InstKind::ConstInt(5, IntWidth::I32), |
| 1174 | }); |
| 1175 | let plus = f.next_value_id(); |
| 1176 | f.register_type(plus, IrType::Int(IntWidth::I32)); |
| 1177 | f.block_mut(body).insts.push(Inst { |
| 1178 | id: plus, |
| 1179 | ty: IrType::Int(IntWidth::I32), |
| 1180 | span, |
| 1181 | kind: InstKind::IAdd(iv, five), |
| 1182 | }); |
| 1183 | let plus64 = f.next_value_id(); |
| 1184 | f.register_type(plus64, IrType::Int(IntWidth::I64)); |
| 1185 | f.block_mut(body).insts.push(Inst { |
| 1186 | id: plus64, |
| 1187 | ty: IrType::Int(IntWidth::I64), |
| 1188 | span, |
| 1189 | kind: InstKind::IntExtend(plus, IntWidth::I64, true), |
| 1190 | }); |
| 1191 | let lo = f.next_value_id(); |
| 1192 | f.register_type(lo, IrType::Int(IntWidth::I64)); |
| 1193 | f.block_mut(body).insts.push(Inst { |
| 1194 | id: lo, |
| 1195 | ty: IrType::Int(IntWidth::I64), |
| 1196 | span, |
| 1197 | kind: InstKind::ConstInt(1, IntWidth::I64), |
| 1198 | }); |
| 1199 | let hi = f.next_value_id(); |
| 1200 | f.register_type(hi, IrType::Int(IntWidth::I64)); |
| 1201 | f.block_mut(body).insts.push(Inst { |
| 1202 | id: hi, |
| 1203 | ty: IrType::Int(IntWidth::I64), |
| 1204 | span, |
| 1205 | kind: InstKind::ConstInt(10, IntWidth::I64), |
| 1206 | }); |
| 1207 | let check = f.next_value_id(); |
| 1208 | f.register_type(check, IrType::Void); |
| 1209 | f.block_mut(body).insts.push(Inst { |
| 1210 | id: check, |
| 1211 | ty: IrType::Void, |
| 1212 | span, |
| 1213 | kind: InstKind::RuntimeCall(RuntimeFunc::CheckBounds, vec![plus64, lo, hi]), |
| 1214 | }); |
| 1215 | let step = f.next_value_id(); |
| 1216 | f.register_type(step, IrType::Int(IntWidth::I32)); |
| 1217 | f.block_mut(body).insts.push(Inst { |
| 1218 | id: step, |
| 1219 | ty: IrType::Int(IntWidth::I32), |
| 1220 | span, |
| 1221 | kind: InstKind::ConstInt(6, IntWidth::I32), |
| 1222 | }); |
| 1223 | let next_iv = f.next_value_id(); |
| 1224 | f.register_type(next_iv, IrType::Int(IntWidth::I32)); |
| 1225 | f.block_mut(body).insts.push(Inst { |
| 1226 | id: next_iv, |
| 1227 | ty: IrType::Int(IntWidth::I32), |
| 1228 | span, |
| 1229 | kind: InstKind::IAdd(iv, step), |
| 1230 | }); |
| 1231 | f.block_mut(body).terminator = Some(Terminator::Branch(header, vec![next_iv])); |
| 1232 | f.block_mut(exit).terminator = Some(Terminator::Return(None)); |
| 1233 | m.add_function(f); |
| 1234 | |
| 1235 | let pass = Bce; |
| 1236 | assert!( |
| 1237 | pass.run(&mut m), |
| 1238 | "iv+5 check should be removed when the trip sequence is only 5 and checked bounds are 1..10" |
| 1239 | ); |
| 1240 | let has_check = m.functions[0].block(body).insts.iter().any(|inst| { |
| 1241 | matches!( |
| 1242 | inst.kind, |
| 1243 | InstKind::RuntimeCall(RuntimeFunc::CheckBounds, _) |
| 1244 | ) |
| 1245 | }); |
| 1246 | assert!(!has_check, "loop body should no longer contain CheckBounds"); |
| 1247 | } |
| 1248 | |
| 1249 | #[test] |
| 1250 | fn loop_index_decomposes_constant_multiplied_iv() { |
| 1251 | let mut f = Function::new("test".into(), vec![], IrType::Void); |
| 1252 | let span = crate::lexer::Span { |
| 1253 | file_id: 0, |
| 1254 | start: crate::lexer::Position { line: 0, col: 0 }, |
| 1255 | end: crate::lexer::Position { line: 0, col: 0 }, |
| 1256 | }; |
| 1257 | |
| 1258 | // Synthesise: i = next_value(); 2*i; (2*i) + 3 — verify the |
| 1259 | // decomposition (base, scale, offset) recovers (i, 2, 3). |
| 1260 | let entry = f.entry; |
| 1261 | let i = f.next_value_id(); |
| 1262 | f.register_type(i, IrType::Int(IntWidth::I32)); |
| 1263 | let two = f.next_value_id(); |
| 1264 | f.register_type(two, IrType::Int(IntWidth::I32)); |
| 1265 | f.block_mut(entry).insts.push(Inst { |
| 1266 | id: two, |
| 1267 | ty: IrType::Int(IntWidth::I32), |
| 1268 | span, |
| 1269 | kind: InstKind::ConstInt(2, IntWidth::I32), |
| 1270 | }); |
| 1271 | let two_i = f.next_value_id(); |
| 1272 | f.register_type(two_i, IrType::Int(IntWidth::I32)); |
| 1273 | f.block_mut(entry).insts.push(Inst { |
| 1274 | id: two_i, |
| 1275 | ty: IrType::Int(IntWidth::I32), |
| 1276 | span, |
| 1277 | kind: InstKind::IMul(two, i), |
| 1278 | }); |
| 1279 | let three = f.next_value_id(); |
| 1280 | f.register_type(three, IrType::Int(IntWidth::I32)); |
| 1281 | f.block_mut(entry).insts.push(Inst { |
| 1282 | id: three, |
| 1283 | ty: IrType::Int(IntWidth::I32), |
| 1284 | span, |
| 1285 | kind: InstKind::ConstInt(3, IntWidth::I32), |
| 1286 | }); |
| 1287 | let two_i_plus_three = f.next_value_id(); |
| 1288 | f.register_type(two_i_plus_three, IrType::Int(IntWidth::I32)); |
| 1289 | f.block_mut(entry).insts.push(Inst { |
| 1290 | id: two_i_plus_three, |
| 1291 | ty: IrType::Int(IntWidth::I32), |
| 1292 | span, |
| 1293 | kind: InstKind::IAdd(two_i, three), |
| 1294 | }); |
| 1295 | |
| 1296 | let (base, scale, offset) = |
| 1297 | loop_index_base_and_offset(&f, two_i_plus_three).expect("should decompose"); |
| 1298 | assert_eq!(base, i, "base should be the unanalysable inner value"); |
| 1299 | assert_eq!(scale, 2, "scale captures the IMul by 2"); |
| 1300 | assert_eq!(offset, 3, "offset captures the +3"); |
| 1301 | } |
| 1302 | } |
| 1303 |