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// RUN: %dexter --fail-lt 1.0 -w \
// RUN: --builder 'clang' --debugger 'lldb' \
// RUN: --cflags "-ffast-math -O2 -g" -- %s
// RUN: %dexter --fail-lt 1.0 -w \
// RUN: --builder 'clang' --debugger 'lldb' \
// RUN: --cflags "-ffast-math -O0 -g" -- %s
// REQUIRES: lldb
// UNSUPPORTED: system-windows
//// Check that the debugging experience with __attribute__((optnone)) at O2
//// matches O0. Test scalar floating point arithmetic with -ffast-math.
//// Example of strength reduction.
//// The division by 10.0f can be rewritten as a multiply by 0.1f.
//// A / 10.f ==> A * 0.1f
//// This is safe with fastmath since we treat the two operations
//// as equally precise. However we don't want this to happen
//// with optnone.
__attribute__((optnone))
float test_fdiv(float A) {
float result;
result = A / 10.f; // DexLabel('fdiv_assign')
return result; // DexLabel('fdiv_ret')
}
// DexExpectWatchValue('A', 4, on_line=ref('fdiv_assign'))
// DexExpectWatchValue('result', '0.400000006', on_line=ref('fdiv_ret'))
//// (A * B) - (A * C) ==> A * (B - C)
__attribute__((optnone))
float test_distributivity(float A, float B, float C) {
float result;
float op1 = A * B;
float op2 = A * C; // DexLabel('distributivity_op2')
result = op1 - op2; // DexLabel('distributivity_result')
return result; // DexLabel('distributivity_ret')
}
// DexExpectWatchValue('op1', '20', on_line=ref('distributivity_op2'))
// DexExpectWatchValue('op2', '24', on_line=ref('distributivity_result'))
// DexExpectWatchValue('result', '-4', on_line=ref('distributivity_ret'))
//// (A + B) + C == A + (B + C)
//// therefore, ((A + B) + C) + (A + (B + C)))
//// can be rewritten as
//// 2.0f * ((A + B) + C)
//// Clang is currently unable to spot this optimization
//// opportunity with fastmath.
__attribute__((optnone))
float test_associativity(float A, float B, float C) {
float result;
float op1 = A + B;
float op2 = B + C;
op1 += C; // DexLabel('associativity_op1')
op2 += A;
result = op1 + op2; // DexLabel('associativity_result')
return result; // DexLabel('associativity_ret')
}
// DexExpectWatchValue('op1', '9', '15', from_line=ref('associativity_op1'), to_line=ref('associativity_result'))
// DexExpectWatchValue('op2', '11', '15', from_line=ref('associativity_op1'), to_line=ref('associativity_result'))
// DexExpectWatchValue('result', '30', on_line=ref('associativity_ret'))
//// With fastmath, the ordering of instructions doesn't matter
//// since we work under the assumption that there is no loss
//// in precision. This simplifies things for the optimizer which
//// can then decide to reorder instructions and fold
//// redundant operations like this:
//// A += 5.0f
//// A -= 5.0f
//// -->
//// A
//// This function can be simplified to a return A + B.
__attribute__((optnone))
float test_simplify_fp_operations(float A, float B) {
float result = A + 10.0f; // DexLabel('fp_operations_result')
result += B; // DexLabel('fp_operations_add')
result -= 10.0f;
return result; // DexLabel('fp_operations_ret')
}
// DexExpectWatchValue('A', '8.25', on_line=ref('fp_operations_result'))
// DexExpectWatchValue('B', '26.3999996', on_line=ref('fp_operations_result'))
// DexExpectWatchValue('result', '18.25', '44.6500015', '34.6500015', from_line=ref('fp_operations_add'), to_line=ref('fp_operations_ret'))
//// Again, this is a simple return A + B.
//// Clang is unable to spot the opportunity to fold the code sequence.
__attribute__((optnone))
float test_simplify_fp_operations_2(float A, float B, float C) {
float result = A + C; // DexLabel('fp_operations_2_result')
result += B;
result -= C; // DexLabel('fp_operations_2_subtract')
return result; // DexLabel('fp_operations_2_ret')
}
// DexExpectWatchValue('A', '9.11999988', on_line=ref('fp_operations_2_result'))
// DexExpectWatchValue('B', '61.050003', on_line=ref('fp_operations_2_result'))
// DexExpectWatchValue('C', '1002.11102', on_line=ref('fp_operations_2_result'))
// DexExpectWatchValue('result', '1072.28101', '70.1699829', from_line=ref('fp_operations_2_subtract'), to_line=ref('fp_operations_2_ret'))
int main() {
float result = test_fdiv(4.0f);
result += test_distributivity(4.0f, 5.0f, 6.0f);
result += test_associativity(4.0f, 5.0f, 6.0f);
result += test_simplify_fp_operations(8.25, result);
result += test_simplify_fp_operations_2(9.12, result, 1002.111);
return static_cast<int>(result);
}
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