Description:
When building the following program with -O1, it outputs 85 whereas without -O1 it outputs 84:

#include <iostream>
#include <stdint.h>

int main()
{
double max = 8.03;
double a = 6.01;
double b = 5;
double c = (double)0xFF / (max - b);

int16_t value = (a - b) * c;
std::cout << "Result = " << value << std::endl;
return 0;
}

The compilation lines I use are really minimal:
- g++ main.cc
vs
- g++ -O1 main.cc

I tried to find which optimization flag was producing this issue but couldn't find any !

- I don't have the issue when I provide explicitely all -O1 optimization flags (obtained with gcc -Q -O1 --help=optimizers | grep "\-f" | grep enabled | awk '{ print $1 }' | xargs) and not -O1 flag
- Among all optimizer flags, I have the issue only with -fsingle-precision-constant, -ffloat-store & -fshort-double but those flags are supposed to be deactivated in -O1 (Note that I didn't test -fpack-struct because it didn't build)

The version of GCC I use is GCC 4.9.2

Regards,
Colin