Hello,
Below is a minimal example of a bug where a variable is set through a reference and then used in a function call. The set value is not used, rather the initial value is observed in the called function. In the call to
getResultCode(float, int32_t) the input quality should be 1.0F. However the if-case returning 0U is not triggered. Instead 1U is returned in the -O3 build.
With the below code, the bug is not observed if we use a `for (int i = 0; i < 2; ++i)` loop, however changing to this loop in the original code still results in incorrect compiled code. Adjusting the size of `
With the below code, the bug is not observed if we use a `for (int i = 0; i < 2; ++i)` loop, however changing to this loop in the original code still results in incorrect compiled code. Adjusting the size of `
uint8_t otherData[128];` seems to impact the reproducibility of the bug.
Compiler version
cl6x --help TMS320C6x C/C++ Compiler v8.3.10 Tools Copyright (c) 1996-2018 Texas Instruments Incorporated
Compilation flags. The bug is observed at -O2 and -O3.
-qq -mv6600 --relaxed_ansi --define=SOC_TDA3XX --keep_unneeded_statics --diag_wrap=off --display_error_number --diag_suppress=556 --diag_suppress=2458 --mem_model:data=far --wchar_t=16 --fp_reassoc=off --float_operations_allowed=all --ramfunc=off --emit_warnings_as_errors -O3 --opt_for_speed=4 -DNDEBUG --symdebug:none --c++14
Header
#ifndef COMPILER_BUG_HPP_
#define COMPILER_BUG_HPP_
#include <cstdint>
struct QualityAndStatus
{
float quality;
uint8_t status;
};
struct Results
{
uint8_t otherData[128];
QualityAndStatus qualityAndStatus[2];
};
void getResults(Results& outResults);
#endif // COMPILER_BUG_HPP_
Source
#include "compiler_bug.hpp"
#include <initializer_list>
namespace
{
uint8_t getResultCode(int32_t const inStatusIdx)
{
constexpr uint8_t STATUS_MAPPINGS[2]{0U, 1U};
return STATUS_MAPPINGS[inStatusIdx];
}
uint8_t getResultCode(float const inQuality, int32_t const inStatusIdx)
{
if (inQuality > 0.0F)
{
return 0U;
}
uint8_t code = getResultCode(inStatusIdx);
if (code == 0U)
{
code = 1U;
}
return code;
}
} // namespace
void getResults(Results& outResults)
{
for (auto const idx : {0, 1})
{
QualityAndStatus& qualityAndStatus = outResults.qualityAndStatus[idx];
qualityAndStatus.quality = 1.0F;
qualityAndStatus.status = getResultCode(qualityAndStatus.quality, 0);
}
}
Test app
#include "compiler_bug.hpp"
#include <xdc/runtime/System.h>
void init()
{
Results results{};
getResults(results);
// Prints 0 with -O1 and 1 with -O2.
System_printf("Result 1: %d\n", results.qualityAndStatus[0].status);
System_printf("Result 2: %d\n", results.qualityAndStatus[1].status);
}
