vect: teach if-convert to predicate __builtin calls [PR122103]

vect: teach if-convert to predicate __builtin calls [PR122103]

The following testcase

void f (float *__restrict c, int *__restrict d, int n)
{
    for (int i = 0; i < n; i++)
    {
      if (d[i] > 1000)
        c[i] = __builtin_sqrtf (c[i]);
    }
}

compiled with -O3 -march=armv9-a -fno-math-errno -ftrapping-math needs to be
predicated on the conditional.  It's invalid to execute the branch and use a
select to extract it later unless using -fno-trapping-math.

This change in if-conversion changes what we used to generate:

  _26 = _4 > 1000;
  _34 = _33 + _2;
  _5 = (float *) _34;
  _6 = .MASK_LOAD (_5, 32B, _26, 0.0);
  _7 = __builtin_sqrtf (_6);
  .MASK_STORE (_5, 32B, _26, _7);

into

  _26 = _4 > 1000;
  _34 = _33 + _2;
  _5 = (float *) _34;
  _6 = .MASK_LOAD (_5, 32B, _26, 0.0);
  _7 = .COND_SQRT (_26, _6, _6);
  .MASK_STORE (_5, 32B, _26, _7);

which correctly results in

.L3:
        ld1w    z0.s, p7/z, [x1, x3, lsl 2]
        cmpgt   p7.s, p7/z, z0.s, z31.s
        ld1w    z30.s, p7/z, [x0, x3, lsl 2]
        fsqrt   z30.s, p7/m, z30.s
        st1w    z30.s, p7, [x0, x3, lsl 2]
        incw    x3
        whilelo p7.s, w3, w2
        b.any   .L3

instead of

.L3:
        ld1w    z0.s, p7/z, [x1, x3, lsl 2]
        cmpgt   p7.s, p7/z, z0.s, z31.s
        ld1w    z30.s, p7/z, [x0, x3, lsl 2]
        fsqrt   z30.s, p6/m, z30.s
        st1w    z30.s, p7, [x0, x3, lsl 2]
        incw    x3
        whilelo p7.s, w3, w2
        b.any   .L3

gcc/ChangeLog:

	PR tree-optimization/122103
	* tree-if-conv.cc (ifcvt_can_predicate): Support gimple_call_builtin_p.
	(if_convertible_stmt_p, predicate_rhs_code,
	predicate_statements): Likewise.

gcc/testsuite/ChangeLog:

	PR tree-optimization/122103
	* gcc.target/aarch64/sve/pr122103_1.c: New test.
	* gcc.target/aarch64/sve/pr122103_2.c: New test.
	* gcc.target/aarch64/sve/pr122103_3.c: New test.