cross-project-tests/debuginfo-tests/dexter-tests/optnone-fastmath.cpp

   1 // RUN: %clang -std=gnu++11 -O2 -ffast-math -g %s -o %t
   2 // RUN: %dexter --fail-lt 1.0 -w \
   3 // RUN:     --binary %t --debugger 'lldb' -- %s
   4 // RUN: %clang -std=gnu++11 -O0 -ffast-math -g %s -o %t
   5 // RUN: %dexter --fail-lt 1.0 -w \
   6 // RUN:     --binary %t --debugger 'lldb' -- %s
   7
   8 // REQUIRES: lldb
   9 // Currently getting intermittent failures on darwin.
  10 // UNSUPPORTED: system-windows, system-darwin
  11
  12 //// Check that the debugging experience with __attribute__((optnone)) at O2
  13 //// matches O0. Test scalar floating point arithmetic with -ffast-math.
  14
  15 //// Example of strength reduction.
  16 //// The division by 10.0f can be rewritten as a multiply by 0.1f.
  17 //// A / 10.f ==> A * 0.1f
  18 //// This is safe with fastmath since we treat the two operations
  19 //// as equally precise. However we don't want this to happen
  20 //// with optnone.
  21 __attribute__((optnone))
  22 float test_fdiv(float A) {
  23   float result;
  24   result = A / 10.f;  // DexLabel('fdiv_assign')
  25   return result;      // DexLabel('fdiv_ret')
  26 }
  27 // DexExpectWatchValue('A', 4, on_line=ref('fdiv_assign'))
  28 // DexExpectWatchValue('result', '0.400000006', on_line=ref('fdiv_ret'))
  29
  30 //// (A * B) - (A * C) ==> A * (B - C)
  31 __attribute__((optnone))
  32 float test_distributivity(float A, float B, float C) {
  33   float result;
  34   float op1 = A * B;
  35   float op2 = A * C;    // DexLabel('distributivity_op2')
  36   result = op1 - op2;   // DexLabel('distributivity_result')
  37   return result;        // DexLabel('distributivity_ret')
  38 }
  39 // DexExpectWatchValue('op1', '20', on_line=ref('distributivity_op2'))
  40 // DexExpectWatchValue('op2', '24', on_line=ref('distributivity_result'))
  41 // DexExpectWatchValue('result', '-4', on_line=ref('distributivity_ret'))
  42
  43 //// (A + B) + C  == A + (B + C)
  44 //// therefore, ((A + B) + C) + (A + (B + C)))
  45 //// can be rewritten as
  46 //// 2.0f * ((A + B) + C)
  47 //// Clang is currently unable to spot this optimization
  48 //// opportunity with fastmath.
  49 __attribute__((optnone))
  50 float test_associativity(float A, float B, float C) {
  51   float result;
  52   float op1 = A + B;
  53   float op2 = B + C;
  54   op1 += C;           // DexLabel('associativity_op1')
  55   op2 += A;
  56   result = op1 + op2; // DexLabel('associativity_result')
  57   return result;      // DexLabel('associativity_ret')
  58 }
  59 // DexExpectWatchValue('op1', '9', '15', from_line=ref('associativity_op1'), to_line=ref('associativity_result'))
  60 // DexExpectWatchValue('op2', '11', '15', from_line=ref('associativity_op1'), to_line=ref('associativity_result'))
  61 // DexExpectWatchValue('result', '30', on_line=ref('associativity_ret'))
  62
  63 //// With fastmath, the ordering of instructions doesn't matter
  64 //// since we work under the assumption that there is no loss
  65 //// in precision. This simplifies things for the optimizer which
  66 //// can then decide to reorder instructions and fold
  67 //// redundant operations like this:
  68 ////   A += 5.0f
  69 ////   A -= 5.0f
  70 ////    -->
  71 ////   A
  72 //// This function can be simplified to a return A + B.
  73 __attribute__((optnone))
  74 float test_simplify_fp_operations(float A, float B) {
  75   float result = A + 10.0f; // DexLabel('fp_operations_result')
  76   result += B;              // DexLabel('fp_operations_add')
  77   result -= 10.0f;
  78   return result;            // DexLabel('fp_operations_ret')
  79 }
  80 // DexExpectWatchValue('A', '8.25', on_line=ref('fp_operations_result'))
  81 // DexExpectWatchValue('B', '26.3999996', on_line=ref('fp_operations_result'))
  82 // DexExpectWatchValue('result', '18.25', '44.6500015', '34.6500015', from_line=ref('fp_operations_add'), to_line=ref('fp_operations_ret'))
  83
  84 //// Again, this is a simple return A + B.
  85 //// Clang is unable to spot the opportunity to fold the code sequence.
  86 __attribute__((optnone))
  87 float test_simplify_fp_operations_2(float A, float B, float C) {
  88   float result = A + C; // DexLabel('fp_operations_2_result')
  89   result += B;
  90   result -= C;          // DexLabel('fp_operations_2_subtract')
  91   return result;        // DexLabel('fp_operations_2_ret')
  92 }
  93 // DexExpectWatchValue('A', '9.11999988', on_line=ref('fp_operations_2_result'))
  94 // DexExpectWatchValue('B', '61.050003', on_line=ref('fp_operations_2_result'))
  95 // DexExpectWatchValue('C', '1002.11102', on_line=ref('fp_operations_2_result'))
  96 // DexExpectWatchValue('result', '1072.28101', '70.1699829', from_line=ref('fp_operations_2_subtract'), to_line=ref('fp_operations_2_ret'))
  97
  98 int main() {
  99   float result = test_fdiv(4.0f);
 100   result += test_distributivity(4.0f, 5.0f, 6.0f);
 101   result += test_associativity(4.0f, 5.0f, 6.0f);
 102   result += test_simplify_fp_operations(8.25, result);
 103   result += test_simplify_fp_operations_2(9.12, result, 1002.111);
 104   return static_cast<int>(result);
 105 }