clang/test/CodeGenCXX/attr-likelihood-if-branch-weights.cpp

   1 // NOTE: Assertions have been autogenerated by utils/update_cc_test_checks.py
   2 // RUN: %clang_cc1 -O1 -disable-llvm-passes -emit-llvm %s -o - -triple=x86_64-- | FileCheck %s
   3
   4 extern volatile bool b;
   5 extern volatile int i;
   6 extern bool A();
   7 extern bool B();
   8
   9 // CHECK-LABEL: @_Z1fv(
  10 // CHECK-NEXT:  entry:
  11 // CHECK-NEXT:    [[RETVAL:%.*]] = alloca i1, align 1
  12 // CHECK-NEXT:    [[TMP0:%.*]] = load volatile i8, ptr @b, align 1, !tbaa [[TBAA2:![0-9]+]], !range [[RNG6:![0-9]+]]
  13 // CHECK-NEXT:    [[TOBOOL:%.*]] = trunc i8 [[TMP0]] to i1
  14 // CHECK-NEXT:    [[TOBOOL_EXPVAL:%.*]] = call i1 @llvm.expect.i1(i1 [[TOBOOL]], i1 true)
  15 // CHECK-NEXT:    br i1 [[TOBOOL_EXPVAL]], label [[IF_THEN:%.*]], label [[IF_END:%.*]]
  16 // CHECK:       if.then:
  17 // CHECK-NEXT:    [[CALL:%.*]] = call noundef zeroext i1 @_Z1Av()
  18 // CHECK-NEXT:    store i1 [[CALL]], ptr [[RETVAL]], align 1
  19 // CHECK-NEXT:    br label [[RETURN:%.*]]
  20 // CHECK:       if.end:
  21 // CHECK-NEXT:    [[CALL1:%.*]] = call noundef zeroext i1 @_Z1Bv()
  22 // CHECK-NEXT:    store i1 [[CALL1]], ptr [[RETVAL]], align 1
  23 // CHECK-NEXT:    br label [[RETURN]]
  24 // CHECK:       return:
  25 // CHECK-NEXT:    [[TMP1:%.*]] = load i1, ptr [[RETVAL]], align 1
  26 // CHECK-NEXT:    ret i1 [[TMP1]]
  27 //
  28 bool f() {
  29   if (b)
  30     [[likely]] {
  31       return A();
  32     }
  33   return B();
  34 }
  35
  36 // CHECK-LABEL: @_Z1gv(
  37 // CHECK-NEXT:  entry:
  38 // CHECK-NEXT:    [[RETVAL:%.*]] = alloca i1, align 1
  39 // CHECK-NEXT:    [[TMP0:%.*]] = load volatile i8, ptr @b, align 1, !tbaa [[TBAA2]], !range [[RNG6]]
  40 // CHECK-NEXT:    [[TOBOOL:%.*]] = trunc i8 [[TMP0]] to i1
  41 // CHECK-NEXT:    [[TOBOOL_EXPVAL:%.*]] = call i1 @llvm.expect.i1(i1 [[TOBOOL]], i1 false)
  42 // CHECK-NEXT:    br i1 [[TOBOOL_EXPVAL]], label [[IF_THEN:%.*]], label [[IF_END:%.*]]
  43 // CHECK:       if.then:
  44 // CHECK-NEXT:    [[CALL:%.*]] = call noundef zeroext i1 @_Z1Av()
  45 // CHECK-NEXT:    store i1 [[CALL]], ptr [[RETVAL]], align 1
  46 // CHECK-NEXT:    br label [[RETURN:%.*]]
  47 // CHECK:       if.end:
  48 // CHECK-NEXT:    [[CALL1:%.*]] = call noundef zeroext i1 @_Z1Bv()
  49 // CHECK-NEXT:    store i1 [[CALL1]], ptr [[RETVAL]], align 1
  50 // CHECK-NEXT:    br label [[RETURN]]
  51 // CHECK:       return:
  52 // CHECK-NEXT:    [[TMP1:%.*]] = load i1, ptr [[RETVAL]], align 1
  53 // CHECK-NEXT:    ret i1 [[TMP1]]
  54 //
  55 bool g() {
  56   if (b)
  57     [[unlikely]] {
  58       return A();
  59     }
  60
  61   return B();
  62 }
  63
  64 // CHECK-LABEL: @_Z1hv(
  65 // CHECK-NEXT:  entry:
  66 // CHECK-NEXT:    [[RETVAL:%.*]] = alloca i1, align 1
  67 // CHECK-NEXT:    [[TMP0:%.*]] = load volatile i8, ptr @b, align 1, !tbaa [[TBAA2]], !range [[RNG6]]
  68 // CHECK-NEXT:    [[TOBOOL:%.*]] = trunc i8 [[TMP0]] to i1
  69 // CHECK-NEXT:    [[TOBOOL_EXPVAL:%.*]] = call i1 @llvm.expect.i1(i1 [[TOBOOL]], i1 false)
  70 // CHECK-NEXT:    br i1 [[TOBOOL_EXPVAL]], label [[IF_THEN:%.*]], label [[IF_END:%.*]]
  71 // CHECK:       if.then:
  72 // CHECK-NEXT:    [[CALL:%.*]] = call noundef zeroext i1 @_Z1Av()
  73 // CHECK-NEXT:    store i1 [[CALL]], ptr [[RETVAL]], align 1
  74 // CHECK-NEXT:    br label [[RETURN:%.*]]
  75 // CHECK:       if.end:
  76 // CHECK-NEXT:    [[CALL1:%.*]] = call noundef zeroext i1 @_Z1Bv()
  77 // CHECK-NEXT:    store i1 [[CALL1]], ptr [[RETVAL]], align 1
  78 // CHECK-NEXT:    br label [[RETURN]]
  79 // CHECK:       return:
  80 // CHECK-NEXT:    [[TMP1:%.*]] = load i1, ptr [[RETVAL]], align 1
  81 // CHECK-NEXT:    ret i1 [[TMP1]]
  82 //
  83 bool h() {
  84   if (b)
  85     [[unlikely]] return A();
  86
  87   return B();
  88 }
  89
  90 // CHECK-LABEL: @_Z8NullStmtv(
  91 // CHECK-NEXT:  entry:
  92 // CHECK-NEXT:    [[TMP0:%.*]] = load volatile i8, ptr @b, align 1, !tbaa [[TBAA2]], !range [[RNG6]]
  93 // CHECK-NEXT:    [[TOBOOL:%.*]] = trunc i8 [[TMP0]] to i1
  94 // CHECK-NEXT:    [[TOBOOL_EXPVAL:%.*]] = call i1 @llvm.expect.i1(i1 [[TOBOOL]], i1 false)
  95 // CHECK-NEXT:    br i1 [[TOBOOL_EXPVAL]], label [[IF_THEN:%.*]], label [[IF_ELSE:%.*]]
  96 // CHECK:       if.then:
  97 // CHECK-NEXT:    br label [[IF_END:%.*]]
  98 // CHECK:       if.else:
  99 // CHECK-NEXT:    store volatile i8 1, ptr @b, align 1, !tbaa [[TBAA2]]
 100 // CHECK-NEXT:    br label [[IF_END]]
 101 // CHECK:       if.end:
 102 // CHECK-NEXT:    ret void
 103 //
 104 void NullStmt() {
 105   if (b)
 106     [[unlikely]];
 107   else {
 108     // Make sure the branches aren't optimized away.
 109     b = true;
 110   }
 111 }
 112
 113 // CHECK-LABEL: @_Z6IfStmtv(
 114 // CHECK-NEXT:  entry:
 115 // CHECK-NEXT:    [[TMP0:%.*]] = load volatile i8, ptr @b, align 1, !tbaa [[TBAA2]], !range [[RNG6]]
 116 // CHECK-NEXT:    [[TOBOOL:%.*]] = trunc i8 [[TMP0]] to i1
 117 // CHECK-NEXT:    [[TOBOOL_EXPVAL:%.*]] = call i1 @llvm.expect.i1(i1 [[TOBOOL]], i1 false)
 118 // CHECK-NEXT:    br i1 [[TOBOOL_EXPVAL]], label [[IF_THEN:%.*]], label [[IF_END2:%.*]]
 119 // CHECK:       if.then:
 120 // CHECK-NEXT:    [[CALL:%.*]] = call noundef zeroext i1 @_Z1Bv()
 121 // CHECK-NEXT:    br i1 [[CALL]], label [[IF_THEN1:%.*]], label [[IF_END:%.*]]
 122 // CHECK:       if.then1:
 123 // CHECK-NEXT:    br label [[IF_END]]
 124 // CHECK:       if.end:
 125 // CHECK-NEXT:    br label [[IF_END2]]
 126 // CHECK:       if.end2:
 127 // CHECK-NEXT:    [[TMP1:%.*]] = load volatile i8, ptr @b, align 1, !tbaa [[TBAA2]], !range [[RNG6]]
 128 // CHECK-NEXT:    [[TOBOOL3:%.*]] = trunc i8 [[TMP1]] to i1
 129 // CHECK-NEXT:    br i1 [[TOBOOL3]], label [[IF_THEN4:%.*]], label [[IF_END8:%.*]]
 130 // CHECK:       if.then4:
 131 // CHECK-NEXT:    [[CALL5:%.*]] = call noundef zeroext i1 @_Z1Bv()
 132 // CHECK-NEXT:    [[CALL5_EXPVAL:%.*]] = call i1 @llvm.expect.i1(i1 [[CALL5]], i1 false)
 133 // CHECK-NEXT:    br i1 [[CALL5_EXPVAL]], label [[IF_THEN6:%.*]], label [[IF_END7:%.*]]
 134 // CHECK:       if.then6:
 135 // CHECK-NEXT:    store volatile i8 0, ptr @b, align 1, !tbaa [[TBAA2]]
 136 // CHECK-NEXT:    br label [[IF_END7]]
 137 // CHECK:       if.end7:
 138 // CHECK-NEXT:    br label [[IF_END8]]
 139 // CHECK:       if.end8:
 140 // CHECK-NEXT:    ret void
 141 //
 142 void IfStmt() {
 143   if (b)
 144     [[unlikely]] if (B()) {}
 145
 146   if (b) {
 147     if (B())
 148       [[unlikely]] { b = false; }
 149   }
 150 }
 151
 152 // CHECK-LABEL: @_Z9WhileStmtv(
 153 // CHECK-NEXT:  entry:
 154 // CHECK-NEXT:    [[TMP0:%.*]] = load volatile i8, ptr @b, align 1, !tbaa [[TBAA2]], !range [[RNG6]]
 155 // CHECK-NEXT:    [[TOBOOL:%.*]] = trunc i8 [[TMP0]] to i1
 156 // CHECK-NEXT:    [[TOBOOL_EXPVAL:%.*]] = call i1 @llvm.expect.i1(i1 [[TOBOOL]], i1 false)
 157 // CHECK-NEXT:    br i1 [[TOBOOL_EXPVAL]], label [[IF_THEN:%.*]], label [[IF_END:%.*]]
 158 // CHECK:       if.then:
 159 // CHECK-NEXT:    br label [[WHILE_COND:%.*]]
 160 // CHECK:       while.cond:
 161 // CHECK-NEXT:    [[CALL:%.*]] = call noundef zeroext i1 @_Z1Bv()
 162 // CHECK-NEXT:    br i1 [[CALL]], label [[WHILE_BODY:%.*]], label [[WHILE_END:%.*]]
 163 // CHECK:       while.body:
 164 // CHECK-NEXT:    br label [[WHILE_COND]], !llvm.loop [[LOOP7:![0-9]+]]
 165 // CHECK:       while.end:
 166 // CHECK-NEXT:    br label [[IF_END]]
 167 // CHECK:       if.end:
 168 // CHECK-NEXT:    [[TMP1:%.*]] = load volatile i8, ptr @b, align 1, !tbaa [[TBAA2]], !range [[RNG6]]
 169 // CHECK-NEXT:    [[TOBOOL1:%.*]] = trunc i8 [[TMP1]] to i1
 170 // CHECK-NEXT:    br i1 [[TOBOOL1]], label [[IF_THEN2:%.*]], label [[IF_END7:%.*]]
 171 // CHECK:       if.then2:
 172 // CHECK-NEXT:    br label [[WHILE_COND3:%.*]]
 173 // CHECK:       while.cond3:
 174 // CHECK-NEXT:    [[CALL4:%.*]] = call noundef zeroext i1 @_Z1Bv()
 175 // CHECK-NEXT:    [[CALL4_EXPVAL:%.*]] = call i1 @llvm.expect.i1(i1 [[CALL4]], i1 false)
 176 // CHECK-NEXT:    br i1 [[CALL4_EXPVAL]], label [[WHILE_BODY5:%.*]], label [[WHILE_END6:%.*]]
 177 // CHECK:       while.body5:
 178 // CHECK-NEXT:    store volatile i8 0, ptr @b, align 1, !tbaa [[TBAA2]]
 179 // CHECK-NEXT:    br label [[WHILE_COND3]], !llvm.loop [[LOOP10:![0-9]+]]
 180 // CHECK:       while.end6:
 181 // CHECK-NEXT:    br label [[IF_END7]]
 182 // CHECK:       if.end7:
 183 // CHECK-NEXT:    ret void
 184 //
 185 void WhileStmt() {
 186   if (b)
 187     [[unlikely]] while (B()) {}
 188
 189   if (b)
 190     while (B())
 191       [[unlikely]] { b = false; }
 192 }
 193
 194 // CHECK-LABEL: @_Z6DoStmtv(
 195 // CHECK-NEXT:  entry:
 196 // CHECK-NEXT:    [[TMP0:%.*]] = load volatile i8, ptr @b, align 1, !tbaa [[TBAA2]], !range [[RNG6]]
 197 // CHECK-NEXT:    [[TOBOOL:%.*]] = trunc i8 [[TMP0]] to i1
 198 // CHECK-NEXT:    [[TOBOOL_EXPVAL:%.*]] = call i1 @llvm.expect.i1(i1 [[TOBOOL]], i1 false)
 199 // CHECK-NEXT:    br i1 [[TOBOOL_EXPVAL]], label [[IF_THEN:%.*]], label [[IF_END:%.*]]
 200 // CHECK:       if.then:
 201 // CHECK-NEXT:    br label [[DO_BODY:%.*]]
 202 // CHECK:       do.body:
 203 // CHECK-NEXT:    br label [[DO_COND:%.*]]
 204 // CHECK:       do.cond:
 205 // CHECK-NEXT:    [[CALL:%.*]] = call noundef zeroext i1 @_Z1Bv()
 206 // CHECK-NEXT:    br i1 [[CALL]], label [[DO_BODY]], label [[DO_END:%.*]], !llvm.loop [[LOOP11:![0-9]+]]
 207 // CHECK:       do.end:
 208 // CHECK-NEXT:    br label [[IF_END]]
 209 // CHECK:       if.end:
 210 // CHECK-NEXT:    [[TMP1:%.*]] = load volatile i8, ptr @b, align 1, !tbaa [[TBAA2]], !range [[RNG6]]
 211 // CHECK-NEXT:    [[TOBOOL1:%.*]] = trunc i8 [[TMP1]] to i1
 212 // CHECK-NEXT:    br i1 [[TOBOOL1]], label [[IF_THEN2:%.*]], label [[IF_END7:%.*]]
 213 // CHECK:       if.then2:
 214 // CHECK-NEXT:    br label [[DO_BODY3:%.*]]
 215 // CHECK:       do.body3:
 216 // CHECK-NEXT:    br label [[DO_COND4:%.*]]
 217 // CHECK:       do.cond4:
 218 // CHECK-NEXT:    [[CALL5:%.*]] = call noundef zeroext i1 @_Z1Bv()
 219 // CHECK-NEXT:    br i1 [[CALL5]], label [[DO_BODY3]], label [[DO_END6:%.*]], !llvm.loop [[LOOP12:![0-9]+]]
 220 // CHECK:       do.end6:
 221 // CHECK-NEXT:    br label [[IF_END7]]
 222 // CHECK:       if.end7:
 223 // CHECK-NEXT:    ret void
 224 //
 225 void DoStmt() {
 226   if (b)
 227     [[unlikely]] do {}
 228     while (B())
 229       ;
 230
 231   if (b)
 232     do
 233       [[unlikely]] {}
 234     while (B());
 235 }
 236
 237 // CHECK-LABEL: @_Z7ForStmtv(
 238 // CHECK-NEXT:  entry:
 239 // CHECK-NEXT:    [[TMP0:%.*]] = load volatile i8, ptr @b, align 1, !tbaa [[TBAA2]], !range [[RNG6]]
 240 // CHECK-NEXT:    [[TOBOOL:%.*]] = trunc i8 [[TMP0]] to i1
 241 // CHECK-NEXT:    [[TOBOOL_EXPVAL:%.*]] = call i1 @llvm.expect.i1(i1 [[TOBOOL]], i1 false)
 242 // CHECK-NEXT:    br i1 [[TOBOOL_EXPVAL]], label [[IF_THEN:%.*]], label [[IF_END:%.*]]
 243 // CHECK:       if.then:
 244 // CHECK-NEXT:    br label [[FOR_COND:%.*]]
 245 // CHECK:       for.cond:
 246 // CHECK-NEXT:    [[CALL:%.*]] = call noundef zeroext i1 @_Z1Bv()
 247 // CHECK-NEXT:    br i1 [[CALL]], label [[FOR_BODY:%.*]], label [[FOR_END:%.*]]
 248 // CHECK:       for.body:
 249 // CHECK-NEXT:    br label [[FOR_COND]], !llvm.loop [[LOOP13:![0-9]+]]
 250 // CHECK:       for.end:
 251 // CHECK-NEXT:    br label [[IF_END]]
 252 // CHECK:       if.end:
 253 // CHECK-NEXT:    [[TMP1:%.*]] = load volatile i8, ptr @b, align 1, !tbaa [[TBAA2]], !range [[RNG6]]
 254 // CHECK-NEXT:    [[TOBOOL1:%.*]] = trunc i8 [[TMP1]] to i1
 255 // CHECK-NEXT:    br i1 [[TOBOOL1]], label [[IF_THEN2:%.*]], label [[IF_END7:%.*]]
 256 // CHECK:       if.then2:
 257 // CHECK-NEXT:    br label [[FOR_COND3:%.*]]
 258 // CHECK:       for.cond3:
 259 // CHECK-NEXT:    [[CALL4:%.*]] = call noundef zeroext i1 @_Z1Bv()
 260 // CHECK-NEXT:    [[CALL4_EXPVAL:%.*]] = call i1 @llvm.expect.i1(i1 [[CALL4]], i1 false)
 261 // CHECK-NEXT:    br i1 [[CALL4_EXPVAL]], label [[FOR_BODY5:%.*]], label [[FOR_END6:%.*]]
 262 // CHECK:       for.body5:
 263 // CHECK-NEXT:    br label [[FOR_COND3]], !llvm.loop [[LOOP14:![0-9]+]]
 264 // CHECK:       for.end6:
 265 // CHECK-NEXT:    br label [[IF_END7]]
 266 // CHECK:       if.end7:
 267 // CHECK-NEXT:    ret void
 268 //
 269 void ForStmt() {
 270   if (b)
 271     [[unlikely]] for (; B();) {}
 272
 273   if (b)
 274     for (; B();)
 275       [[unlikely]] {}
 276 }
 277
 278 // CHECK-LABEL: @_Z8GotoStmtv(
 279 // CHECK-NEXT:  entry:
 280 // CHECK-NEXT:    [[TMP0:%.*]] = load volatile i8, ptr @b, align 1, !tbaa [[TBAA2]], !range [[RNG6]]
 281 // CHECK-NEXT:    [[TOBOOL:%.*]] = trunc i8 [[TMP0]] to i1
 282 // CHECK-NEXT:    [[TOBOOL_EXPVAL:%.*]] = call i1 @llvm.expect.i1(i1 [[TOBOOL]], i1 false)
 283 // CHECK-NEXT:    br i1 [[TOBOOL_EXPVAL]], label [[IF_THEN:%.*]], label [[IF_ELSE:%.*]]
 284 // CHECK:       if.then:
 285 // CHECK-NEXT:    br label [[END:%.*]]
 286 // CHECK:       if.else:
 287 // CHECK-NEXT:    store volatile i8 1, ptr @b, align 1, !tbaa [[TBAA2]]
 288 // CHECK-NEXT:    br label [[IF_END:%.*]]
 289 // CHECK:       if.end:
 290 // CHECK-NEXT:    br label [[END]]
 291 // CHECK:       end:
 292 // CHECK-NEXT:    ret void
 293 //
 294 void GotoStmt() {
 295   if (b)
 296     [[unlikely]] goto end;
 297   else {
 298     // Make sure the branches aren't optimized away.
 299     b = true;
 300   }
 301 end:;
 302 }
 303
 304 // CHECK-LABEL: @_Z10ReturnStmtv(
 305 // CHECK-NEXT:  entry:
 306 // CHECK-NEXT:    [[TMP0:%.*]] = load volatile i8, ptr @b, align 1, !tbaa [[TBAA2]], !range [[RNG6]]
 307 // CHECK-NEXT:    [[TOBOOL:%.*]] = trunc i8 [[TMP0]] to i1
 308 // CHECK-NEXT:    [[TOBOOL_EXPVAL:%.*]] = call i1 @llvm.expect.i1(i1 [[TOBOOL]], i1 false)
 309 // CHECK-NEXT:    br i1 [[TOBOOL_EXPVAL]], label [[IF_THEN:%.*]], label [[IF_ELSE:%.*]]
 310 // CHECK:       if.then:
 311 // CHECK-NEXT:    br label [[IF_END:%.*]]
 312 // CHECK:       if.else:
 313 // CHECK-NEXT:    store volatile i8 1, ptr @b, align 1, !tbaa [[TBAA2]]
 314 // CHECK-NEXT:    br label [[IF_END]]
 315 // CHECK:       if.end:
 316 // CHECK-NEXT:    ret void
 317 //
 318 void ReturnStmt() {
 319   if (b)
 320     [[unlikely]] return;
 321   else {
 322     // Make sure the branches aren't optimized away.
 323     b = true;
 324   }
 325 }
 326
 327 // CHECK-LABEL: @_Z10SwitchStmtv(
 328 // CHECK-NEXT:  entry:
 329 // CHECK-NEXT:    [[TMP0:%.*]] = load volatile i8, ptr @b, align 1, !tbaa [[TBAA2]], !range [[RNG6]]
 330 // CHECK-NEXT:    [[TOBOOL:%.*]] = trunc i8 [[TMP0]] to i1
 331 // CHECK-NEXT:    [[TOBOOL_EXPVAL:%.*]] = call i1 @llvm.expect.i1(i1 [[TOBOOL]], i1 false)
 332 // CHECK-NEXT:    br i1 [[TOBOOL_EXPVAL]], label [[IF_THEN:%.*]], label [[IF_ELSE:%.*]]
 333 // CHECK:       if.then:
 334 // CHECK-NEXT:    [[TMP1:%.*]] = load volatile i32, ptr @i, align 4, !tbaa [[TBAA15:![0-9]+]]
 335 // CHECK-NEXT:    switch i32 [[TMP1]], label [[SW_EPILOG:%.*]] [
 336 // CHECK-NEXT:    ]
 337 // CHECK:       sw.epilog:
 338 // CHECK-NEXT:    br label [[IF_END:%.*]]
 339 // CHECK:       if.else:
 340 // CHECK-NEXT:    store volatile i8 1, ptr @b, align 1, !tbaa [[TBAA2]]
 341 // CHECK-NEXT:    br label [[IF_END]]
 342 // CHECK:       if.end:
 343 // CHECK-NEXT:    [[TMP2:%.*]] = load volatile i8, ptr @b, align 1, !tbaa [[TBAA2]], !range [[RNG6]]
 344 // CHECK-NEXT:    [[TOBOOL1:%.*]] = trunc i8 [[TMP2]] to i1
 345 // CHECK-NEXT:    br i1 [[TOBOOL1]], label [[IF_THEN2:%.*]], label [[IF_ELSE4:%.*]]
 346 // CHECK:       if.then2:
 347 // CHECK-NEXT:    [[TMP3:%.*]] = load volatile i32, ptr @i, align 4, !tbaa [[TBAA15]]
 348 // CHECK-NEXT:    switch i32 [[TMP3]], label [[SW_EPILOG3:%.*]] [
 349 // CHECK-NEXT:    ]
 350 // CHECK:       sw.epilog3:
 351 // CHECK-NEXT:    br label [[IF_END5:%.*]]
 352 // CHECK:       if.else4:
 353 // CHECK-NEXT:    store volatile i8 1, ptr @b, align 1, !tbaa [[TBAA2]]
 354 // CHECK-NEXT:    br label [[IF_END5]]
 355 // CHECK:       if.end5:
 356 // CHECK-NEXT:    ret void
 357 //
 358 void SwitchStmt() {
 359   if (b)
 360     [[unlikely]] switch (i) {}
 361   else {
 362     // Make sure the branches aren't optimized away.
 363     b = true;
 364   }
 365   if (b)
 366     switch (i)
 367       [[unlikely]] {}
 368   else {
 369     // Make sure the branches aren't optimized away.
 370     b = true;
 371   }
 372 }
 373