clang/test/CodeGen/branch-target-layout.c

   1 // RUN: %clang_cc1 %s -O3 -emit-llvm -o - | FileCheck %s
   2 //
   3 // PR13214
   4 // No assumption may be made about the order that a frontend emits branch
   5 // targets (basic blocks). However, the backend's basic block layout makes an
   6 // attempt to preserve source order of control flow, and any bias toward source
   7 // order must start with the frontend.
   8 //
   9 // Note that the frontend inverts branches to simplify the condition, so the
  10 // order of a branch instruction's labels cannot be used as a source order bias.
  11
  12 void calla(void);
  13 void callb(void);
  14 void callc(void);
  15
  16 // CHECK: @test1
  17 // CHECK: @calla
  18 // CHECK: @callb
  19 // CHECK: @callc
  20 // CHECK: ret void
  21 void test1(int a) {
  22   if (a)
  23     calla();
  24   else
  25     callb();
  26   callc();
  27 }
  28
  29 // CHECK: @test2
  30 // CHECK: @callb
  31 // CHECK: @calla
  32 // CHECK: @callc
  33 // CHECK: ret void
  34 void test2(int a) {
  35   if (!a)
  36     callb();
  37   else
  38     calla();
  39   callc();
  40 }