On Thu, Jan 11, 2024 at 9:50 AM <pan2...@intel.com> wrote:
>
> From: Pan Li <pan2...@intel.com>
>
> The insert_var_expansion_initialization depends on the
> HONOR_SIGNED_ZEROS to initialize the unrolling variables
> to +0.0f when -0.0f and no-signed-option. Unfortunately,
> we should always keep the -0.0f here because:
>
> * The -0.0f is always the correct initial value.
> * We need to support the target that always honor signed zero.
>
> Thus, we need to leverage MODE_HAS_SIGNED_ZEROS when initialize
> instead of HONOR_SIGNED_ZEROS. Then the target/backend can
> decide to honor the no-signed-zero or not.
>
> We also removed the testcase pr30957-1.c, as it makes undefined behavior
> whether the return value is positive or negative.
>
> The below tests are passed for this patch:
>
> * The riscv regression tests.
> * The aarch64 regression tests.
> * The x86 bootstrap and regression tests.
OK
> gcc/ChangeLog:
>
> * loop-unroll.cc (insert_var_expansion_initialization): Leverage
> MODE_HAS_SIGNED_ZEROS for expansion variable initialization.
>
> gcc/testsuite/ChangeLog:
>
> * gcc.dg/pr30957-1.c: Remove.
>
> Signed-off-by: Pan Li <pan2...@intel.com>
> ---
> gcc/loop-unroll.cc | 4 ++--
> gcc/testsuite/gcc.dg/pr30957-1.c | 36 --------------------------------
> 2 files changed, 2 insertions(+), 38 deletions(-)
> delete mode 100644 gcc/testsuite/gcc.dg/pr30957-1.c
>
> diff --git a/gcc/loop-unroll.cc b/gcc/loop-unroll.cc
> index 4176a21e308..bfdfe6c2bb7 100644
> --- a/gcc/loop-unroll.cc
> +++ b/gcc/loop-unroll.cc
> @@ -1855,7 +1855,7 @@ insert_var_expansion_initialization (struct
> var_to_expand *ve,
> rtx var, zero_init;
> unsigned i;
> machine_mode mode = GET_MODE (ve->reg);
> - bool honor_signed_zero_p = HONOR_SIGNED_ZEROS (mode);
> + bool has_signed_zero_p = MODE_HAS_SIGNED_ZEROS (mode);
>
> if (ve->var_expansions.length () == 0)
> return;
> @@ -1869,7 +1869,7 @@ insert_var_expansion_initialization (struct
> var_to_expand *ve,
> case MINUS:
> FOR_EACH_VEC_ELT (ve->var_expansions, i, var)
> {
> - if (honor_signed_zero_p)
> + if (has_signed_zero_p)
> zero_init = simplify_gen_unary (NEG, mode, CONST0_RTX (mode),
> mode);
> else
> zero_init = CONST0_RTX (mode);
> diff --git a/gcc/testsuite/gcc.dg/pr30957-1.c
> b/gcc/testsuite/gcc.dg/pr30957-1.c
> deleted file mode 100644
> index 564410913ab..00000000000
> --- a/gcc/testsuite/gcc.dg/pr30957-1.c
> +++ /dev/null
> @@ -1,36 +0,0 @@
> -/* { dg-do run { xfail { mmix-*-* } } } */
> -/* We don't (and don't want to) perform this optimisation on soft-float
> targets,
> - where each addition is a library call. /
> -/* { dg-require-effective-target hard_float } */
> -/* -fassociative-math requires -fno-trapping-math and -fno-signed-zeros. */
> -/* { dg-options "-O2 -funroll-loops -fassociative-math -fno-trapping-math
> -fno-signed-zeros -fvariable-expansion-in-unroller -fdump-rtl-loop2_unroll" }
> */
> -
> -extern void abort (void);
> -extern void exit (int);
> -
> -float __attribute__((noinline))
> -foo (float d, int n)
> -{
> - unsigned i;
> - float accum = d;
> -
> - for (i = 0; i < n; i++)
> - accum += d;
> -
> - return accum;
> -}
> -
> -int
> -main ()
> -{
> - /* When compiling standard compliant we expect foo to return -0.0. But the
> - variable expansion during unrolling optimization (for this testcase
> enabled
> - by non-compliant -fassociative-math) instantiates copy(s) of the
> - accumulator which it initializes with +0.0. Hence we expect that foo
> - returns +0.0. */
> - if (__builtin_copysignf (1.0, foo (0.0 / -5.0, 10)) != 1.0)
> - abort ();
> - exit (0);
> -}
> -
> -/* { dg-final { scan-rtl-dump "Expanding Accumulator" "loop2_unroll" { xfail
> mmix-*-* } } } */
> --
> 2.34.1
>
