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 8 define void @multiexit(i1 %x) { 9 ; CHECK-NEXT: entry: float = 1.0, int = [[ENTRY:[0-9]+]] 10 entry: 11 br label %loop.1 12 13 ; CHECK-NEXT: loop.1: float = 2.0, 14 loop.1: 15 br i1 %x, label %exit.1, label %loop.2, !prof !0 16 17 ; CHECK-NEXT: loop.2: float = 1.75, 18 loop.2: 19 br i1 %x, label %exit.2, label %loop.1, !prof !1 20 21 ; CHECK-NEXT: exit.1: float = 0.25, 22 exit.1: 23 br label %return 24 25 ; CHECK-NEXT: exit.2: float = 0.75, 26 exit.2: 27 br label %return 28 29 ; CHECK-NEXT: return: float = 1.0, int = [[ENTRY]] 30 return: 31 ret void 32 } 33 34 !0 = metadata !{metadata !"branch_weights", i32 1, i32 7} 35 !1 = metadata !{metadata !"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. 93 define void @multientry(i1 %x) { 94 ; CHECK-LABEL: Printing analysis {{.*}} for function 'multientry': 95 ; CHECK-NEXT: block-frequency-info: multientry 96 entry: 97 ; CHECK-NEXT: entry: float = 1.0, int = [[ENTRY:[0-9]+]] 98 br i1 %x, label %c1, label %c2, !prof !2 99 100 c1: 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 !2 104 105 c2: 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 !2 109 110 exit: 111 ; CHECK-NEXT: exit: float = 1.0, int = [[ENTRY]] 112 ret void 113 } 114 115 !2 = metadata !{metadata !"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. 136 define void @crossloops(i2 %x) { 137 ; CHECK-LABEL: Printing analysis {{.*}} for function 'crossloops': 138 ; CHECK-NEXT: block-frequency-info: crossloops 139 entry: 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 !3 143 144 c1: 145 ; CHECK-NEXT: c1: float = 1.0, 146 switch i2 %x, label %exit [ i2 1, label %c1 147 i2 2, label %c2 ], !prof !3 148 149 c2: 150 ; CHECK-NEXT: c2: float = 1.0, 151 switch i2 %x, label %exit [ i2 1, label %c1 152 i2 2, label %c2 ], !prof !3 153 154 exit: 155 ; CHECK-NEXT: exit: float = 1.0, int = [[ENTRY]] 156 ret void 157 } 158 159 !3 = metadata !{metadata !"branch_weights", i32 2, i32 2, i32 2} 160 161 ; A true loop with irreducible control flow inside. 162 define 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 165 entry: 166 ; CHECK-NEXT: entry: float = 1.0, int = [[ENTRY:[0-9]+]] 167 br label %loop 168 169 loop: 170 ; CHECK-NEXT: loop: float = 4.0, int = [[HEAD:[0-9]+]] 171 br i1 %x, label %left, label %right, !prof !4 172 173 left: 174 ; CHECK-NEXT: left: float = 8.0, 175 br i1 %x, label %right, label %loop.end, !prof !5 176 177 right: 178 ; CHECK-NEXT: right: float = 8.0, 179 br i1 %x, label %left, label %loop.end, !prof !5 180 181 loop.end: 182 ; CHECK-NEXT: loop.end: float = 4.0, int = [[HEAD]] 183 br i1 %x, label %loop, label %exit, !prof !5 184 185 exit: 186 ; CHECK-NEXT: exit: float = 1.0, int = [[ENTRY]] 187 ret void 188 } 189 !4 = metadata !{metadata !"branch_weights", i32 1, i32 1} 190 !5 = metadata !{metadata !"branch_weights", i32 3, i32 1} 191 192 ; Two unrelated irreducible SCCs. 193 define void @two_sccs(i1 %x) { 194 ; CHECK-LABEL: Printing analysis {{.*}} for function 'two_sccs': 195 ; CHECK-NEXT: block-frequency-info: two_sccs 196 entry: 197 ; CHECK-NEXT: entry: float = 1.0, int = [[ENTRY:[0-9]+]] 198 br i1 %x, label %a, label %b, !prof !6 199 200 a: 201 ; CHECK-NEXT: a: float = 0.75, 202 br i1 %x, label %a.left, label %a.right, !prof !7 203 204 a.left: 205 ; CHECK-NEXT: a.left: float = 1.5, 206 br i1 %x, label %a.right, label %exit, !prof !6 207 208 a.right: 209 ; CHECK-NEXT: a.right: float = 1.5, 210 br i1 %x, label %a.left, label %exit, !prof !6 211 212 b: 213 ; CHECK-NEXT: b: float = 0.25, 214 br i1 %x, label %b.left, label %b.right, !prof !7 215 216 b.left: 217 ; CHECK-NEXT: b.left: float = 0.625, 218 br i1 %x, label %b.right, label %exit, !prof !8 219 220 b.right: 221 ; CHECK-NEXT: b.right: float = 0.625, 222 br i1 %x, label %b.left, label %exit, !prof !8 223 224 exit: 225 ; CHECK-NEXT: exit: float = 1.0, int = [[ENTRY]] 226 ret void 227 } 228 !6 = metadata !{metadata !"branch_weights", i32 3, i32 1} 229 !7 = metadata !{metadata !"branch_weights", i32 1, i32 1} 230 !8 = metadata !{metadata !"branch_weights", i32 4, i32 1} 231 232 ; A true loop inside irreducible control flow. 233 define 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 236 entry: 237 ; CHECK-NEXT: entry: float = 1.0, int = [[ENTRY:[0-9]+]] 238 br i1 %x, label %left, label %right, !prof !9 239 240 left: 241 ; CHECK-NEXT: left: float = 2.0, 242 br i1 %x, label %right, label %exit, !prof !10 243 244 right: 245 ; CHECK-NEXT: right: float = 2.0, int = [[RIGHT:[0-9]+]] 246 br label %loop 247 248 loop: 249 ; CHECK-NEXT: loop: float = 6.0, 250 br i1 %x, label %loop, label %right.end, !prof !11 251 252 right.end: 253 ; CHECK-NEXT: right.end: float = 2.0, int = [[RIGHT]] 254 br i1 %x, label %left, label %exit, !prof !10 255 256 exit: 257 ; CHECK-NEXT: exit: float = 1.0, int = [[ENTRY]] 258 ret void 259 } 260 !9 = metadata !{metadata !"branch_weights", i32 1, i32 1} 261 !10 = metadata !{metadata !"branch_weights", i32 3, i32 1} 262 !11 = metadata !{metadata !"branch_weights", i32 2, i32 1} 263 264 ; Irreducible control flow in a branch that's in a true loop. 265 define 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 268 entry: 269 ; CHECK-NEXT: entry: float = 1.0, int = [[ENTRY:[0-9]+]] 270 br label %loop 271 272 loop: 273 ; CHECK-NEXT: loop: float = 2.0, int = [[LOOP:[0-9]+]] 274 br i1 %x, label %normal, label %irreducible.entry, !prof !12 275 276 normal: 277 ; CHECK-NEXT: normal: float = 1.5, 278 br label %loop.end 279 280 irreducible.entry: 281 ; CHECK-NEXT: irreducible.entry: float = 0.5, int = [[IRREDUCIBLE:[0-9]+]] 282 br i1 %x, label %left, label %right, !prof !13 283 284 left: 285 ; CHECK-NEXT: left: float = 1.0, 286 br i1 %x, label %right, label %irreducible.exit, !prof !12 287 288 right: 289 ; CHECK-NEXT: right: float = 1.0, 290 br i1 %x, label %left, label %irreducible.exit, !prof !12 291 292 irreducible.exit: 293 ; CHECK-NEXT: irreducible.exit: float = 0.5, int = [[IRREDUCIBLE]] 294 br label %loop.end 295 296 loop.end: 297 ; CHECK-NEXT: loop.end: float = 2.0, int = [[LOOP]] 298 br i1 %x, label %loop, label %exit, !prof !13 299 300 exit: 301 ; CHECK-NEXT: exit: float = 1.0, int = [[ENTRY]] 302 ret void 303 } 304 !12 = metadata !{metadata !"branch_weights", i32 3, i32 1} 305 !13 = metadata !{metadata !"branch_weights", i32 1, i32 1} 306 307 ; Irreducible control flow between two true loops. 308 define 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 311 entry: 312 ; CHECK-NEXT: entry: float = 1.0, int = [[ENTRY:[0-9]+]] 313 br label %loop 314 315 loop: 316 ; CHECK-NEXT: loop: float = 3.0, int = [[LOOP:[0-9]+]] 317 br i1 %x, label %normal, label %irreducible, !prof !14 318 319 normal: 320 ; CHECK-NEXT: normal: float = 2.0, 321 br label %loop.end 322 323 irreducible: 324 ; CHECK-NEXT: irreducible: float = 1.0, 325 br i1 %x, label %left, label %right, !prof !15 326 327 left: 328 ; CHECK-NEXT: left: float = 2.0, 329 br i1 %x, label %right, label %loop.end, !prof !16 330 331 right: 332 ; CHECK-NEXT: right: float = 2.0, int = [[RIGHT:[0-9]+]] 333 br label %right.loop 334 335 right.loop: 336 ; CHECK-NEXT: right.loop: float = 10.0, 337 br i1 %x, label %right.loop, label %right.end, !prof !17 338 339 right.end: 340 ; CHECK-NEXT: right.end: float = 2.0, int = [[RIGHT]] 341 br i1 %x, label %left, label %loop.end, !prof !16 342 343 loop.end: 344 ; CHECK-NEXT: loop.end: float = 3.0, int = [[LOOP]] 345 br i1 %x, label %loop, label %exit, !prof !14 346 347 exit: 348 ; CHECK-NEXT: exit: float = 1.0, int = [[ENTRY]] 349 ret void 350 } 351 !14 = metadata !{metadata !"branch_weights", i32 2, i32 1} 352 !15 = metadata !{metadata !"branch_weights", i32 1, i32 1} 353 !16 = metadata !{metadata !"branch_weights", i32 3, i32 1} 354 !17 = metadata !{metadata !"branch_weights", i32 4, i32 1} 355 356 ; An irreducible SCC with a non-header. 357 define void @nonheader(i1 %x) { 358 ; CHECK-LABEL: Printing analysis {{.*}} for function 'nonheader': 359 ; CHECK-NEXT: block-frequency-info: nonheader 360 entry: 361 ; CHECK-NEXT: entry: float = 1.0, int = [[ENTRY:[0-9]+]] 362 br i1 %x, label %left, label %right, !prof !18 363 364 left: 365 ; CHECK-NEXT: left: float = 1.0, 366 br i1 %x, label %bottom, label %exit, !prof !19 367 368 right: 369 ; CHECK-NEXT: right: float = 1.0, 370 br i1 %x, label %bottom, label %exit, !prof !20 371 372 bottom: 373 ; CHECK-NEXT: bottom: float = 1.0, 374 br i1 %x, label %left, label %right, !prof !18 375 376 exit: 377 ; CHECK-NEXT: exit: float = 1.0, int = [[ENTRY]] 378 ret void 379 } 380 !18 = metadata !{metadata !"branch_weights", i32 1, i32 1} 381 !19 = metadata !{metadata !"branch_weights", i32 1, i32 3} 382 !20 = metadata !{metadata !"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. 390 define void @nonentry_header(i1 %x, i2 %y) { 391 ; CHECK-LABEL: Printing analysis {{.*}} for function 'nonentry_header': 392 ; CHECK-NEXT: block-frequency-info: nonentry_header 393 entry: 394 ; CHECK-NEXT: entry: float = 1.0, int = [[ENTRY:[0-9]+]] 395 br i1 %x, label %left, label %right, !prof !21 396 397 left: 398 ; CHECK-NEXT: left: float = 3.0, 399 br i1 %x, label %top, label %bottom, !prof !22 400 401 right: 402 ; CHECK-NEXT: right: float = 3.0, 403 br i1 %x, label %top, label %bottom, !prof !22 404 405 top: 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 !23 410 411 bottom: 412 ; CHECK-NEXT: bottom: float = 4.5, 413 br label %top 414 415 exit: 416 ; CHECK-NEXT: exit: float = 1.0, int = [[ENTRY]] 417 ret void 418 } 419 !21 = metadata !{metadata !"branch_weights", i32 2, i32 1} 420 !22 = metadata !{metadata !"branch_weights", i32 1, i32 1} 421 !23 = metadata !{metadata !"branch_weights", i32 8, i32 1, i32 3, i32 12} 422
