[Bug middle-end/61225] [5/6/7 Regression] Several new failures after r210458 on x86_64-*-* with -m32

[rguenther at suse dot de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61225

--- Comment #32 from rguenther at suse dot de <rguenther at suse dot de> ---
On Mon, 13 Feb 2017, ubizjak at gmail dot com wrote:

> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61225
> 
> Uroš Bizjak <ubizjak at gmail dot com> changed:
> 
>            What    |Removed                     |Added
> ----------------------------------------------------------------------------
>                  CC|                            |rguenth at gcc dot gnu.org
> 
> --- Comment #31 from Uroš Bizjak <ubizjak at gmail dot com> ---
> What I find interesting here is, that following testcase:
> 
> --cut here--
> void foo (void *);
> 
> #define F(T, OP, OPN) \
> T *                     \
> f##T##OPN (T *x, T y)   \
> {                       \
>   *x OP y;              \
>   if (!*x)              \
>     foo (x);            \
>   return x;             \
> }
> 
> #define G(T) \
> F (T, |=, or)           \
> F (T, ^=, xor)
> 
> G (int)
> --cut here--
> 
> in fact also fails on x86_64 (-Os, -O2):
> 
> fintxor:
> .LFB1:
>         movl    (%rdi), %eax
>         pushq   %rbx
> .LCFI2:
>         movq    %rdi, %rbx
>         movl    %eax, %edx
>         xorl    %esi, %edx
>         cmpl    %esi, %eax
>         movl    %edx, (%rdi)
>         jne     .L6
>         call    foo
> .L6:
>         movq    %rbx, %rax
>         popq    %rbx
> .LCFI3:
>         ret
> 
> The failure is not detected, since the test scans only for TEST insn, not also
> for CMP.
> 
> The difference between these two functions is already in the .optimized tree
> dump between fintor (good):
> 
> fintor (int * x, int y)
> {
>   int _1;
>   int _2;
> 
>   <bb 2> [100.00%]:
>   _1 = *x_5(D);
>   _2 = _1 | y_6(D);
>   *x_5(D) = _2;
>   if (_2 == 0)
>     goto <bb 3>; [36.64%]
>   else
>     goto <bb 4>; [63.36%]
> 
>   <bb 3> [36.64%]:
>   foo (x_5(D));
> 
>   <bb 4> [100.00%]:
>   return x_5(D);
> 
> }
> 
> and fintxor (bad):
> 
> fintxor (int * x, int y)
> {
>   int _1;
>   int _2;
> 
>   <bb 2> [100.00%]:
>   _1 = *x_5(D);
>   _2 = _1 ^ y_6(D);
>   *x_5(D) = _2;
>   if (_1 == y_6(D))

That's from

/* Equality compare simplifications from fold_binary  */
(for cmp (eq ne)
...
 /* (X ^ Y) == 0 becomes X == Y, and (X ^ Y) != 0 becomes X != Y.  */
 (simplify
  (cmp (bit_xor @0 @1) integer_zerop)
  (cmp @0 @1))

not considering other uses.