On Tue, Dec 16, 2014 at 9:37 PM, Jan Hubicka <hubi...@ucw.cz> wrote:
> Hi,
> I have optimized inliner to take advantage that the heap is now in sreal and
> found that using small numbers leads to excessive time (7% of WPA) spent by
> sreal::normalize. This is because the normalization is implemented by loops
> that are unnecesary and can account considerable time when tripped too often.
> This patch implements it via floor_log2 and brings normalize inline. The
> motivation is to make the constructors from compile time constants to be
> optimized into constant write.
>
> I broke normalize into normalize_up/normalize_down and the hot path to futher
> aid inlininig (w/o profile inliner will most of time inline everything
> together
> but still it is better than one big function with profile feedback at least.)
>
> Bootstrapped/regtested x86_64-linux, OK?
Ok.
Thanks,
Richard.
> Honza
>
> * sreal.h (sreal::normalize): Implement inline.
> (sreal::normalize_up): New function.
> (sreal::normalize_down): New function.
> Index: sreal.h
> ===================================================================
> --- sreal.h (revision 218765)
> +++ sreal.h (working copy)
> @@ -116,7 +116,9 @@ public:
> }
>
> private:
> - void normalize ();
> + inline void normalize ();
> + inline void normalize_up ();
> + inline void normalize_down ();
> void shift_right (int amount);
> static sreal signedless_plus (const sreal &a, const sreal &b, bool
> negative);
> static sreal signedless_minus (const sreal &a, const sreal &b, bool
> negative);
> @@ -178,4 +180,85 @@ inline sreal operator>> (const sreal &a,
> return a.shift (-exp);
> }
>
> +/* Make significant to be >= SREAL_MIN_SIG.
> +
> + Make this separate method so inliner can handle hot path better. */
> +
> +inline void
> +sreal::normalize_up ()
> +{
> + int64_t s = m_sig < 0 ? -1 : 1;
> + unsigned HOST_WIDE_INT sig = absu_hwi (m_sig);
> + int shift = SREAL_PART_BITS - 2 - floor_log2 (sig);
> +
> + gcc_checking_assert (shift > 0);
> + sig <<= shift;
> + m_exp -= shift;
> + gcc_checking_assert (sig <= SREAL_MAX_SIG && sig >= SREAL_MIN_SIG);
> +
> + /* Check underflow. */
> + if (m_exp < -SREAL_MAX_EXP)
> + {
> + m_exp = -SREAL_MAX_EXP;
> + sig = 0;
> + }
> + if (s == -1)
> + m_sig = -sig;
> + else
> + m_sig = sig;
> +}
> +
> +/* Make significant to be <= SREAL_MAX_SIG.
> +
> + Make this separate method so inliner can handle hot path better. */
> +
> +inline void
> +sreal::normalize_down ()
> +{
> + int64_t s = m_sig < 0 ? -1 : 1;
> + int last_bit;
> + unsigned HOST_WIDE_INT sig = absu_hwi (m_sig);
> + int shift = floor_log2 (sig) - SREAL_PART_BITS + 2;
> +
> + gcc_checking_assert (shift > 0);
> + last_bit = (sig >> (shift-1)) & 1;
> + sig >>= shift;
> + m_exp += shift;
> + gcc_checking_assert (sig <= SREAL_MAX_SIG && sig >= SREAL_MIN_SIG);
> +
> + /* Round the number. */
> + sig += last_bit;
> + if (sig > SREAL_MAX_SIG)
> + {
> + sig >>= 1;
> + m_exp++;
> + }
> +
> + /* Check overflow. */
> + if (m_exp > SREAL_MAX_EXP)
> + {
> + m_exp = SREAL_MAX_EXP;
> + sig = SREAL_MAX_SIG;
> + }
> + if (s == -1)
> + m_sig = -sig;
> + else
> + m_sig = sig;
> +}
> +
> +/* Normalize *this; the hot path. */
> +
> +inline void
> +sreal::normalize ()
> +{
> + unsigned HOST_WIDE_INT sig = absu_hwi (m_sig);
> +
> + if (sig == 0)
> + m_exp = -SREAL_MAX_EXP;
> + else if (sig > SREAL_MAX_SIG)
> + normalize_down ();
> + else if (sig < SREAL_MIN_SIG)
> + normalize_up ();
> +}
> +
> #endif
> Index: sreal.c
> ===================================================================
> --- sreal.c (revision 218765)
> +++ sreal.c (working copy)
> @@ -96,64 +96,6 @@ sreal::shift_right (int s)
> m_sig >>= s;
> }
>
> -/* Normalize *this. */
> -
> -void
> -sreal::normalize ()
> -{
> - int64_t s = m_sig < 0 ? -1 : 1;
> - unsigned HOST_WIDE_INT sig = absu_hwi (m_sig);
> -
> - if (sig == 0)
> - {
> - m_exp = -SREAL_MAX_EXP;
> - }
> - else if (sig < SREAL_MIN_SIG)
> - {
> - do
> - {
> - sig <<= 1;
> - m_exp--;
> - }
> - while (sig < SREAL_MIN_SIG);
> -
> - /* Check underflow. */
> - if (m_exp < -SREAL_MAX_EXP)
> - {
> - m_exp = -SREAL_MAX_EXP;
> - sig = 0;
> - }
> - }
> - else if (sig > SREAL_MAX_SIG)
> - {
> - int last_bit;
> - do
> - {
> - last_bit = sig & 1;
> - sig >>= 1;
> - m_exp++;
> - }
> - while (sig > SREAL_MAX_SIG);
> -
> - /* Round the number. */
> - sig += last_bit;
> - if (sig > SREAL_MAX_SIG)
> - {
> - sig >>= 1;
> - m_exp++;
> - }
> -
> - /* Check overflow. */
> - if (m_exp > SREAL_MAX_EXP)
> - {
> - m_exp = SREAL_MAX_EXP;
> - sig = SREAL_MAX_SIG;
> - }
> - }
> -
> - m_sig = s * sig;
> -}
> -
> /* Return integer value of *this. */
>
> int64_t
