[Bug target/66703] [4.9/5/6] gcc.target/i386/readeflags-1.c aborts on -march=i586 or on -miamcu

["hjl.tools at gmail dot com" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66703

H.J. Lu <hjl.tools at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|---                         |WONTFIX

--- Comment #1 from H.J. Lu <hjl.tools at gmail dot com> ---
We have

unsigned int
readeflags_test (unsigned int a, unsigned int b)
{
  unsigned x = (a == b);
  return __builtin_ia32_readeflags_u32 ();
}

For

unsigned x = (a == b);

-march=i586 generates:



;; _3 = a_1(D) == b_2(D);

(insn 5 4 6 (set (reg:SI 90)
        (mem/c:SI (reg/f:SI 81 virtual-incoming-args) [0 a+0 S4 A32])) y.i:4 -1
     (nil))

(insn 6 5 7 (set (reg:CCZ 17 flags)
        (compare:CCZ (reg:SI 90)
            (mem/c:SI (plus:SI (reg/f:SI 81 virtual-incoming-args)
                    (const_int 4 [0x4])) [0 b+0 S4 A32]))) y.i:4 -1
     (nil))

(insn 7 6 0 (set (reg:QI 87 [ D.1413 ])
        (eq:QI (reg:CCZ 17 flags)
            (const_int 0 [0]))) y.i:4 -1
     (nil))

;; x_4 = (unsigned int) _3;

(insn 8 7 9 (parallel [
            (set (reg:SI 91)
                (zero_extend:SI (reg:QI 87 [ D.1413 ])))
            (clobber (reg:CC 17 flags))
        ]) y.i:4 -1
     (nil))

(insn 9 8 0 (set (mem/c:SI (plus:SI (reg/f:SI 82 virtual-stack-vars)
                (const_int -4 [0xfffffffffffffffc])) [0 x+0 S4 A32])
        (reg:SI 91)) y.i:4 -1
     (nil))

EFLAGS register is clobbered and __builtin_ia32_readeflags_u32
returns clobbered value.  So the testcase is expected to fail
if zero-extend bool to unsigned int clobbers EFLAGS register.  Since
we have

/* X86_TUNE_ZERO_EXTEND_WITH_AND: Use AND instruction instead
   of mozbl/movwl.  */  
DEF_TUNE (X86_TUNE_ZERO_EXTEND_WITH_AND, "zero_extend_with_and",
          m_486 | m_PENT)

This test should fail with -march=i486, -march=i586 or -miamcu.