[Bug tree-optimization/91734] New: gcc skip an if statement with "-O1 -ffast-math"

[chinoune.mehdi at hotmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91734

            Bug ID: 91734
           Summary: gcc skip an if statement  with "-O1 -ffast-math"
           Product: gcc
           Version: 9.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: chinoune.mehdi at hotmail dot com
  Target Milestone: ---

Building this program with gcc [8,9] "-O1 -ffast-math" makes the result
overflows.

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

void foo(float complex z, float *y){
    float const sqrt_flt_min = sqrtf( FLT_MIN );
    float az;
    az = cabsf(z);
    //az = cabsf(z/sqrt_flt_min) * sqrt_flt_min;
    if( az<FLT_MIN ) az = cabsf(z/sqrt_flt_min) * sqrt_flt_min;
    printf("az = %.8e\n",az);
    *y = 1.f/az;
}

int main(){
    float complex z;
    float y;

    z = 1.e-19f + 0.*I;
    foo(z,&y);
    printf("y = %.7e\n",y);

    return 0;
}

gcc-9 -O1 -fno-math-errno -funsafe-math-optimizations -ffinite-math-only
-fdump-tree-optimized cbug_skip_if.c -o test.x -lm
./test.x
az = 0.00000000e+00
y = inf

cbug_skip_if.c.231t.optimized

;; Function foo (foo, funcdef_no=32, decl_uid=4150, cgraph_uid=33,
symbol_order=32)

foo (complex float z, float * y)
{
  double _3;
  float _4;
  float cabs_17;
  float cabs_18;
  float cabs_19;
  float cabs_20;
  float cabs_21;
  float powroot_22;

  <bb 2> [local count: 1073741824]:
  cabs_17 = REALPART_EXPR <z_6(D)>;
  cabs_18 = cabs_17 * cabs_17;
  cabs_19 = IMAGPART_EXPR <z_6(D)>;
  cabs_20 = cabs_19 * cabs_19;
  cabs_21 = cabs_18 + cabs_20;
  powroot_22 = __builtin_sqrtf (cabs_21);
  _3 = (double) powroot_22;
  __printf_chk (1, "az = %.8e\n", _3);
  _4 = 1.0e+0 / powroot_22;
  *y_10(D) = _4;
  return;

}

;; Function main (main, funcdef_no=33, decl_uid=4154, cgraph_uid=34,
symbol_order=33) (executed once)

main ()
{
  float y;
  float y.0_1;
  double _2;

  <bb 2> [local count: 1073741824]:
  foo (__complex__
(9.9999996826552253889678874634872052240552875446155667305e-20, 0.0), &y);
  y.0_1 = y;
  _2 = (double) y.0_1;
  __printf_chk (1, "y = %.7e\n", _2);
  y ={v} {CLOBBER};
  return 0;

}

There is no if statement!