clang/test/Profile/c-counter-overflows.c

   1 // Test that big branch weights get scaled down to 32-bits, rather than just
   2 // truncated.
   3
   4 // RUN: llvm-profdata merge %S/Inputs/c-counter-overflows.proftext -o %t.profdata
   5 // RUN: %clang_cc1 -triple x86_64-apple-macosx10.9 -main-file-name c-counter-overflows.c %s -o - -emit-llvm -fprofile-instrument-use-path=%t.profdata | FileCheck %s
   6
   7 typedef unsigned long long uint64_t;
   8
   9 int main(int argc, const char *argv[]) {
  10   // Need counts higher than 32-bits.
  11   // CHECK: br {{.*}} !prof ![[FOR:[0-9]+]]
  12   // max   = 0xffffffff0
  13   // scale = 0xffffffff0 / 0xffffffff + 1 = 17
  14   // loop-body: 0xffffffff0 / 17 + 1 = 0xf0f0f0f0 + 1 = 4042322161 => -252645135
  15   // loop-exit: 0x000000001 / 17 + 1 = 0x00000000 + 1 =          1 =>          1
  16   for (uint64_t I = 0; I < 0xffffffff0; ++I) {
  17     // max   = 0xffffffff * 15 = 0xefffffff1
  18     // scale = 0xefffffff1 / 0xffffffff + 1 = 16
  19     // CHECK: br {{.*}} !prof ![[IF:[0-9]+]]
  20     if (I & 0xf) {
  21       // 0xefffffff1 / 16 + 1 = 0xefffffff + 1 = 4026531840 => -268435456
  22     } else {
  23       // 0x0ffffffff / 16 + 1 = 0x0fffffff + 1 =  268435456 =>  268435456
  24     }
  25
  26     // max   = 0xffffffff * 5 = 0x4fffffffb
  27     // scale = 0x4fffffffb / 0xffffffff + 1 = 6
  28     // CHECK: ], !prof ![[SWITCH:[0-9]+]]
  29     switch ((I & 0xf) / 5) {
  30     case 0:
  31       // 0x4fffffffb / 6 = 0xd5555554 + 1 = 3579139413 => -715827883
  32       break;
  33     case 1:
  34       // 0x4fffffffb / 6 = 0xd5555554 + 1 = 3579139413 => -715827883
  35       break;
  36     case 2:
  37       // 0x4fffffffb / 6 = 0xd5555554 + 1 = 3579139413 => -715827883
  38       break;
  39     default:
  40       // 0x0ffffffff / 6 = 0x2aaaaaaa + 1 =  715827883 =>  715827883
  41       break;
  42     }
  43   }
  44   return 0;
  45 }
  46
  47 // CHECK-DAG: ![[FOR]] = !{!"branch_weights", i32 -252645135, i32 1}
  48 // CHECK-DAG: ![[IF]]  = !{!"branch_weights", i32 -268435456, i32 268435456}
  49 // CHECK-DAG: ![[SWITCH]] = !{!"branch_weights", i32 715827883, i32 -715827883, i32 -715827883, i32 -715827883}