1; RUN: opt < %s -analyze -block-freq | FileCheck %s 2 3; A loop with multiple exits isn't irreducible. It should be handled 4; correctly. 5; 6; CHECK-LABEL: Printing analysis {{.*}} for function 'multiexit': 7; CHECK-NEXT: block-frequency-info: multiexit 8define void @multiexit(i1 %x) { 9; CHECK-NEXT: entry: float = 1.0, int = [[ENTRY:[0-9]+]] 10entry: 11 br label %loop.1 12 13; CHECK-NEXT: loop.1: float = 2.0, 14loop.1: 15 br i1 %x, label %exit.1, label %loop.2, !prof !0 16 17; CHECK-NEXT: loop.2: float = 1.75, 18loop.2: 19 br i1 %x, label %exit.2, label %loop.1, !prof !1 20 21; CHECK-NEXT: exit.1: float = 0.25, 22exit.1: 23 br label %return 24 25; CHECK-NEXT: exit.2: float = 0.75, 26exit.2: 27 br label %return 28 29; CHECK-NEXT: return: float = 1.0, int = [[ENTRY]] 30return: 31 ret void 32} 33 34!0 = !{!"branch_weights", i32 1, i32 7} 35!1 = !{!"branch_weights", i32 3, i32 4} 36 37; Irreducible control flow 38; ======================== 39; 40; LoopInfo defines a loop as a non-trivial SCC dominated by a single block, 41; called the header. A given loop, L, can have sub-loops, which are loops 42; within the subgraph of L that excludes the header. 43; 44; In addition to loops, -block-freq has limited support for irreducible SCCs, 45; which are SCCs with multiple entry blocks. Irreducible SCCs are discovered 46; on they fly, and modelled as loops with multiple headers. 47; 48; The headers of irreducible sub-SCCs consist of its entry blocks and all nodes 49; that are targets of a backedge within it (excluding backedges within true 50; sub-loops). 51; 52; -block-freq is currently designed to act like a block is inserted that 53; intercepts all the edges to the headers. All backedges and entries point to 54; this block. Its successors are the headers, which split the frequency 55; evenly. 56; 57; There are a number of testcases below. Only the first two have detailed 58; explanations. 59; 60; Testcase #1 61; =========== 62; 63; In this case c1 and c2 should have frequencies of 15/7 and 13/7, 64; respectively. To calculate this, consider assigning 1.0 to entry, and 65; distributing frequency iteratively (to infinity). At the first iteration, 66; entry gives 3/4 to c1 and 1/4 to c2. At every step after, c1 and c2 give 3/4 67; of what they have to each other. Somehow, all of it comes out to exit. 68; 69; c1 = 3/4 + 1/4*3/4 + 3/4*3^2/4^2 + 1/4*3^3/4^3 + 3/4*3^3/4^3 + ... 70; c2 = 1/4 + 3/4*3/4 + 1/4*3^2/4^2 + 3/4*3^3/4^3 + 1/4*3^3/4^3 + ... 71; 72; Simplify by splitting up the odd and even terms of the series and taking out 73; factors so that the infite series matches: 74; 75; c1 = 3/4 *(9^0/16^0 + 9^1/16^1 + 9^2/16^2 + ...) 76; + 3/16*(9^0/16^0 + 9^1/16^1 + 9^2/16^2 + ...) 77; c2 = 1/4 *(9^0/16^0 + 9^1/16^1 + 9^2/16^2 + ...) 78; + 9/16*(9^0/16^0 + 9^1/16^1 + 9^2/16^2 + ...) 79; 80; c1 = 15/16*(9^0/16^0 + 9^1/16^1 + 9^2/16^2 + ...) 81; c2 = 13/16*(9^0/16^0 + 9^1/16^1 + 9^2/16^2 + ...) 82; 83; Since this geometric series sums to 16/7: 84; 85; c1 = 15/7 86; c2 = 13/7 87; 88; If we treat c1 and c2 as members of the same loop, the exit frequency of the 89; loop as a whole is 1/4, so the loop scale should be 4. Summing c1 and c2 90; gives 28/7, or 4.0, which is nice confirmation of the math above. 91; 92; -block-freq currently treats the two nodes as equals. 93define void @multientry(i1 %x) { 94; CHECK-LABEL: Printing analysis {{.*}} for function 'multientry': 95; CHECK-NEXT: block-frequency-info: multientry 96entry: 97; CHECK-NEXT: entry: float = 1.0, int = [[ENTRY:[0-9]+]] 98 br i1 %x, label %c1, label %c2, !prof !2 99 100c1: 101; CHECK-NEXT: c1: float = 2.0, 102; The "correct" answer is: float = 2.142857{{[0-9]*}}, 103 br i1 %x, label %c2, label %exit, !prof !2 104 105c2: 106; CHECK-NEXT: c2: float = 2.0, 107; The "correct" answer is: float = 1.857142{{[0-9]*}}, 108 br i1 %x, label %c1, label %exit, !prof !2 109 110exit: 111; CHECK-NEXT: exit: float = 1.0, int = [[ENTRY]] 112 ret void 113} 114 115!2 = !{!"branch_weights", i32 3, i32 1} 116 117; Testcase #2 118; =========== 119; 120; In this case c1 and c2 should be treated as equals in a single loop. The 121; exit frequency is 1/3, so the scaling factor for the loop should be 3.0. The 122; loop is entered 2/3 of the time, and c1 and c2 split the total loop frequency 123; evenly (1/2), so they should each have frequencies of 1.0 (3.0*2/3*1/2). 124; Another way of computing this result is by assigning 1.0 to entry and showing 125; that c1 and c2 should accumulate frequencies of: 126; 127; 1/3 + 2/9 + 4/27 + 8/81 + ... 128; 2^0/3^1 + 2^1/3^2 + 2^2/3^3 + 2^3/3^4 + ... 129; 130; At the first step, c1 and c2 each get 1/3 of the entry. At each subsequent 131; step, c1 and c2 each get 1/3 of what's left in c1 and c2 combined. This 132; infinite series sums to 1. 133; 134; Since the currently algorithm *always* assumes entry blocks are equal, 135; -block-freq gets the right answers here. 136define void @crossloops(i2 %x) { 137; CHECK-LABEL: Printing analysis {{.*}} for function 'crossloops': 138; CHECK-NEXT: block-frequency-info: crossloops 139entry: 140; CHECK-NEXT: entry: float = 1.0, int = [[ENTRY:[0-9]+]] 141 switch i2 %x, label %exit [ i2 1, label %c1 142 i2 2, label %c2 ], !prof !3 143 144c1: 145; CHECK-NEXT: c1: float = 1.0, 146 switch i2 %x, label %exit [ i2 1, label %c1 147 i2 2, label %c2 ], !prof !3 148 149c2: 150; CHECK-NEXT: c2: float = 1.0, 151 switch i2 %x, label %exit [ i2 1, label %c1 152 i2 2, label %c2 ], !prof !3 153 154exit: 155; CHECK-NEXT: exit: float = 1.0, int = [[ENTRY]] 156 ret void 157} 158 159!3 = !{!"branch_weights", i32 2, i32 2, i32 2} 160 161; A true loop with irreducible control flow inside. 162define void @loop_around_irreducible(i1 %x) { 163; CHECK-LABEL: Printing analysis {{.*}} for function 'loop_around_irreducible': 164; CHECK-NEXT: block-frequency-info: loop_around_irreducible 165entry: 166; CHECK-NEXT: entry: float = 1.0, int = [[ENTRY:[0-9]+]] 167 br label %loop 168 169loop: 170; CHECK-NEXT: loop: float = 4.0, int = [[HEAD:[0-9]+]] 171 br i1 %x, label %left, label %right, !prof !4 172 173left: 174; CHECK-NEXT: left: float = 8.0, 175 br i1 %x, label %right, label %loop.end, !prof !5 176 177right: 178; CHECK-NEXT: right: float = 8.0, 179 br i1 %x, label %left, label %loop.end, !prof !5 180 181loop.end: 182; CHECK-NEXT: loop.end: float = 4.0, int = [[HEAD]] 183 br i1 %x, label %loop, label %exit, !prof !5 184 185exit: 186; CHECK-NEXT: exit: float = 1.0, int = [[ENTRY]] 187 ret void 188} 189!4 = !{!"branch_weights", i32 1, i32 1} 190!5 = !{!"branch_weights", i32 3, i32 1} 191 192; Two unrelated irreducible SCCs. 193define void @two_sccs(i1 %x) { 194; CHECK-LABEL: Printing analysis {{.*}} for function 'two_sccs': 195; CHECK-NEXT: block-frequency-info: two_sccs 196entry: 197; CHECK-NEXT: entry: float = 1.0, int = [[ENTRY:[0-9]+]] 198 br i1 %x, label %a, label %b, !prof !6 199 200a: 201; CHECK-NEXT: a: float = 0.75, 202 br i1 %x, label %a.left, label %a.right, !prof !7 203 204a.left: 205; CHECK-NEXT: a.left: float = 1.5, 206 br i1 %x, label %a.right, label %exit, !prof !6 207 208a.right: 209; CHECK-NEXT: a.right: float = 1.5, 210 br i1 %x, label %a.left, label %exit, !prof !6 211 212b: 213; CHECK-NEXT: b: float = 0.25, 214 br i1 %x, label %b.left, label %b.right, !prof !7 215 216b.left: 217; CHECK-NEXT: b.left: float = 0.625, 218 br i1 %x, label %b.right, label %exit, !prof !8 219 220b.right: 221; CHECK-NEXT: b.right: float = 0.625, 222 br i1 %x, label %b.left, label %exit, !prof !8 223 224exit: 225; CHECK-NEXT: exit: float = 1.0, int = [[ENTRY]] 226 ret void 227} 228!6 = !{!"branch_weights", i32 3, i32 1} 229!7 = !{!"branch_weights", i32 1, i32 1} 230!8 = !{!"branch_weights", i32 4, i32 1} 231 232; A true loop inside irreducible control flow. 233define void @loop_inside_irreducible(i1 %x) { 234; CHECK-LABEL: Printing analysis {{.*}} for function 'loop_inside_irreducible': 235; CHECK-NEXT: block-frequency-info: loop_inside_irreducible 236entry: 237; CHECK-NEXT: entry: float = 1.0, int = [[ENTRY:[0-9]+]] 238 br i1 %x, label %left, label %right, !prof !9 239 240left: 241; CHECK-NEXT: left: float = 2.0, 242 br i1 %x, label %right, label %exit, !prof !10 243 244right: 245; CHECK-NEXT: right: float = 2.0, int = [[RIGHT:[0-9]+]] 246 br label %loop 247 248loop: 249; CHECK-NEXT: loop: float = 6.0, 250 br i1 %x, label %loop, label %right.end, !prof !11 251 252right.end: 253; CHECK-NEXT: right.end: float = 2.0, int = [[RIGHT]] 254 br i1 %x, label %left, label %exit, !prof !10 255 256exit: 257; CHECK-NEXT: exit: float = 1.0, int = [[ENTRY]] 258 ret void 259} 260!9 = !{!"branch_weights", i32 1, i32 1} 261!10 = !{!"branch_weights", i32 3, i32 1} 262!11 = !{!"branch_weights", i32 2, i32 1} 263 264; Irreducible control flow in a branch that's in a true loop. 265define void @loop_around_branch_with_irreducible(i1 %x) { 266; CHECK-LABEL: Printing analysis {{.*}} for function 'loop_around_branch_with_irreducible': 267; CHECK-NEXT: block-frequency-info: loop_around_branch_with_irreducible 268entry: 269; CHECK-NEXT: entry: float = 1.0, int = [[ENTRY:[0-9]+]] 270 br label %loop 271 272loop: 273; CHECK-NEXT: loop: float = 2.0, int = [[LOOP:[0-9]+]] 274 br i1 %x, label %normal, label %irreducible.entry, !prof !12 275 276normal: 277; CHECK-NEXT: normal: float = 1.5, 278 br label %loop.end 279 280irreducible.entry: 281; CHECK-NEXT: irreducible.entry: float = 0.5, int = [[IRREDUCIBLE:[0-9]+]] 282 br i1 %x, label %left, label %right, !prof !13 283 284left: 285; CHECK-NEXT: left: float = 1.0, 286 br i1 %x, label %right, label %irreducible.exit, !prof !12 287 288right: 289; CHECK-NEXT: right: float = 1.0, 290 br i1 %x, label %left, label %irreducible.exit, !prof !12 291 292irreducible.exit: 293; CHECK-NEXT: irreducible.exit: float = 0.5, int = [[IRREDUCIBLE]] 294 br label %loop.end 295 296loop.end: 297; CHECK-NEXT: loop.end: float = 2.0, int = [[LOOP]] 298 br i1 %x, label %loop, label %exit, !prof !13 299 300exit: 301; CHECK-NEXT: exit: float = 1.0, int = [[ENTRY]] 302 ret void 303} 304!12 = !{!"branch_weights", i32 3, i32 1} 305!13 = !{!"branch_weights", i32 1, i32 1} 306 307; Irreducible control flow between two true loops. 308define void @loop_around_branch_with_irreducible_around_loop(i1 %x) { 309; CHECK-LABEL: Printing analysis {{.*}} for function 'loop_around_branch_with_irreducible_around_loop': 310; CHECK-NEXT: block-frequency-info: loop_around_branch_with_irreducible_around_loop 311entry: 312; CHECK-NEXT: entry: float = 1.0, int = [[ENTRY:[0-9]+]] 313 br label %loop 314 315loop: 316; CHECK-NEXT: loop: float = 3.0, int = [[LOOP:[0-9]+]] 317 br i1 %x, label %normal, label %irreducible, !prof !14 318 319normal: 320; CHECK-NEXT: normal: float = 2.0, 321 br label %loop.end 322 323irreducible: 324; CHECK-NEXT: irreducible: float = 1.0, 325 br i1 %x, label %left, label %right, !prof !15 326 327left: 328; CHECK-NEXT: left: float = 2.0, 329 br i1 %x, label %right, label %loop.end, !prof !16 330 331right: 332; CHECK-NEXT: right: float = 2.0, int = [[RIGHT:[0-9]+]] 333 br label %right.loop 334 335right.loop: 336; CHECK-NEXT: right.loop: float = 10.0, 337 br i1 %x, label %right.loop, label %right.end, !prof !17 338 339right.end: 340; CHECK-NEXT: right.end: float = 2.0, int = [[RIGHT]] 341 br i1 %x, label %left, label %loop.end, !prof !16 342 343loop.end: 344; CHECK-NEXT: loop.end: float = 3.0, int = [[LOOP]] 345 br i1 %x, label %loop, label %exit, !prof !14 346 347exit: 348; CHECK-NEXT: exit: float = 1.0, int = [[ENTRY]] 349 ret void 350} 351!14 = !{!"branch_weights", i32 2, i32 1} 352!15 = !{!"branch_weights", i32 1, i32 1} 353!16 = !{!"branch_weights", i32 3, i32 1} 354!17 = !{!"branch_weights", i32 4, i32 1} 355 356; An irreducible SCC with a non-header. 357define void @nonheader(i1 %x) { 358; CHECK-LABEL: Printing analysis {{.*}} for function 'nonheader': 359; CHECK-NEXT: block-frequency-info: nonheader 360entry: 361; CHECK-NEXT: entry: float = 1.0, int = [[ENTRY:[0-9]+]] 362 br i1 %x, label %left, label %right, !prof !18 363 364left: 365; CHECK-NEXT: left: float = 1.0, 366 br i1 %x, label %bottom, label %exit, !prof !19 367 368right: 369; CHECK-NEXT: right: float = 1.0, 370 br i1 %x, label %bottom, label %exit, !prof !20 371 372bottom: 373; CHECK-NEXT: bottom: float = 1.0, 374 br i1 %x, label %left, label %right, !prof !18 375 376exit: 377; CHECK-NEXT: exit: float = 1.0, int = [[ENTRY]] 378 ret void 379} 380!18 = !{!"branch_weights", i32 1, i32 1} 381!19 = !{!"branch_weights", i32 1, i32 3} 382!20 = !{!"branch_weights", i32 3, i32 1} 383 384; An irreducible SCC with an irreducible sub-SCC. In the current version of 385; -block-freq, this means an extra header. 386; 387; This testcases uses non-trivial branch weights. The CHECK statements here 388; will start to fail if we change -block-freq to be more accurate. Currently, 389; we expect left, right and top to be treated as equal headers. 390define void @nonentry_header(i1 %x, i2 %y) { 391; CHECK-LABEL: Printing analysis {{.*}} for function 'nonentry_header': 392; CHECK-NEXT: block-frequency-info: nonentry_header 393entry: 394; CHECK-NEXT: entry: float = 1.0, int = [[ENTRY:[0-9]+]] 395 br i1 %x, label %left, label %right, !prof !21 396 397left: 398; CHECK-NEXT: left: float = 3.0, 399 br i1 %x, label %top, label %bottom, !prof !22 400 401right: 402; CHECK-NEXT: right: float = 3.0, 403 br i1 %x, label %top, label %bottom, !prof !22 404 405top: 406; CHECK-NEXT: top: float = 3.0, 407 switch i2 %y, label %exit [ i2 0, label %left 408 i2 1, label %right 409 i2 2, label %bottom ], !prof !23 410 411bottom: 412; CHECK-NEXT: bottom: float = 4.5, 413 br label %top 414 415exit: 416; CHECK-NEXT: exit: float = 1.0, int = [[ENTRY]] 417 ret void 418} 419!21 = !{!"branch_weights", i32 2, i32 1} 420!22 = !{!"branch_weights", i32 1, i32 1} 421!23 = !{!"branch_weights", i32 8, i32 1, i32 3, i32 12} 422