[Bug c/114746] With FLT_EVAL_METHOD = 2, -fexcess-precision=fast reduces the precision of floating-point constants

[vincent-gcc at vinc17 dot net via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114746

--- Comment #1 from Vincent Lefèvre <vincent-gcc at vinc17 dot net> ---
There is the same issue with constant floating-point expressions.

Consider the following program given at
  https://github.com/llvm/llvm-project/issues/89128

#include <float.h>
#include <stdio.h>

static double const_init = 1.0 + (DBL_EPSILON/2) + (DBL_EPSILON/2);
int main() {
    double nonconst_init = 1.0;
    nonconst_init = nonconst_init + (DBL_EPSILON/2) + (DBL_EPSILON/2);
    printf("FLT_EVAL_METHOD = %d\n", FLT_EVAL_METHOD);
    printf("const: %g\n", const_init - 1.0);
    printf("nonconst: %g\n", (double)nonconst_init - 1.0);
}

With -m32 -mno-sse, one gets

FLT_EVAL_METHOD = 2
const: 0
nonconst: 2.22045e-16

instead of

FLT_EVAL_METHOD = 2
const: 2.22045e-16
nonconst: 2.22045e-16