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[Bug math/14471] New: Inaccurate y0f function on x86_32


http://sourceware.org/bugzilla/show_bug.cgi?id=14471

             Bug #: 14471
           Summary: Inaccurate y0f function on x86_32
           Product: glibc
           Version: 2.17
            Status: NEW
          Severity: normal
          Priority: P2
         Component: math
        AssignedTo: unassigned@sourceware.org
        ReportedBy: liubov.dmitrieva@gmail.com
    Classification: Unclassified


Test case:

// gcc main.c -std=c99 -lm -m32

#include <stdio.h>
#include <fenv.h>
#include <stdlib.h>  // abs function for int argument

extern float y0f(float);
extern double y0(double);

#define i32(a)    (((int*)&(a))[0])

int main() {
    float a,r1,r2;

    i32(a)=0x4155c70d;    //argument

    fesetround(FE_TONEAREST);

    r1 = y0f(a);  //actual result
    r2 = y0(a);   //actual result 2

    printf("inputs: a = (0x%08x)\t%e\n", i32(a), a);
    printf("actual    = (0x%08x)\t%.13e\n", i32(r1), r1);
    printf("expected  = (0x%08x)\t%.13e\n", i32(r2), r2);
    printf("error     = %d ulp\n", abs(i32(r1) - i32(r2)));

    return 0;
}

Result:

(core 2 for example):


-bash-4.2$ gcc main_y0f.c -lm -odo -m32
-bash-4.2$ ./do
inputs: a = (0x4155c70d)        1.336110e+01
actual    = (0xb4801c51)        -2.3862460807322e-07
expected  = (0xb47ff7c8)        -2.3838867946324e-07
error     = 9353 ulp

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