On Wed, 29 Aug 2018, Jan Hubicka wrote:
> Hi,
> this patch reduces memory use of sreal by converting m_sig from int64_t to
> int32_t. This requires me to reduce SREAL_PART_BITS from 32 to 31 so there is
> space for sign. There is comment "SREAL_PART_BITS has to be an even number."
> but I found no reason for that comment. It is possible that I missed something
> obvious but I read the normalization and operations and didn't noticed
> anything
> that would rely on this.
>
> Of course we need 2*SREAL_PART_BITS for temporary calcuations so perhaps at
> some time SREAL_PART_BITS meant that.
>
> There is some effect on code of tramp3d but manual inspection of dumps did not
> show anything important, just small differences in roundoff errors.
>
> Bootstrapped/regtested x86_64-linux, OK?
OK.
> Honza
>
> * sreal.h (SREAL_PART_BITS): Change to 31; remove seemingly unnecessary
> comment that it has to be even number.
> (class sreal): Change m_sig type to int32_t.
> * sreal.c (sreal::dump, sreal::to_int, opreator+, operator-): Use
> int64_t for temporary calculations.
> (sreal_verify_basics): Drop one bit from minimum and maximum.
> Index: sreal.h
> ===================================================================
> --- sreal.h (revision 263952)
> +++ sreal.h (working copy)
> @@ -20,8 +20,7 @@ along with GCC; see the file COPYING3.
> #ifndef GCC_SREAL_H
> #define GCC_SREAL_H
>
> -/* SREAL_PART_BITS has to be an even number. */
> -#define SREAL_PART_BITS 32
> +#define SREAL_PART_BITS 31
>
> #define UINT64_BITS 64
>
> @@ -137,7 +136,7 @@ private:
> static sreal signedless_plus (const sreal &a, const sreal &b, bool
> negative);
> static sreal signedless_minus (const sreal &a, const sreal &b, bool
> negative);
>
> - int64_t m_sig; /* Significant. */
> + int32_t m_sig; /* Significant. */
> signed int m_exp; /* Exponent. */
> };
>
> Index: sreal.c
> ===================================================================
> --- sreal.c (revision 263952)
> +++ sreal.c (working copy)
> @@ -64,7 +64,7 @@ along with GCC; see the file COPYING3.
> void
> sreal::dump (FILE *file) const
> {
> - fprintf (file, "(%" PRIi64 " * 2^%d)", m_sig, m_exp);
> + fprintf (file, "(%" PRIi64 " * 2^%d)", (int64_t)m_sig, m_exp);
> }
>
> DEBUG_FUNCTION void
> @@ -114,7 +114,7 @@ sreal::to_int () const
> if (m_exp >= SREAL_PART_BITS)
> return sign * INTTYPE_MAXIMUM (int64_t);
> if (m_exp > 0)
> - return sign * (SREAL_ABS (m_sig) << m_exp);
> + return sign * (SREAL_ABS ((int64_t)m_sig) << m_exp);
> if (m_exp < 0)
> return m_sig >> -m_exp;
> return m_sig;
> @@ -167,7 +167,7 @@ sreal::operator+ (const sreal &other) co
> bb = &tmp;
> }
>
> - r_sig = a_p->m_sig + bb->m_sig;
> + r_sig = a_p->m_sig + (int64_t)bb->m_sig;
> sreal r (r_sig, r_exp);
> return r;
> }
> @@ -211,7 +211,7 @@ sreal::operator- (const sreal &other) co
> bb = &tmp;
> }
>
> - r_sig = sign * ((int64_t) a_p->m_sig - bb->m_sig);
> + r_sig = sign * ((int64_t) a_p->m_sig - (int64_t)bb->m_sig);
> sreal r (r_sig, r_exp);
> return r;
> }
> @@ -277,15 +277,15 @@ namespace selftest {
> static void
> sreal_verify_basics (void)
> {
> - sreal minimum = INT_MIN;
> - sreal maximum = INT_MAX;
> + sreal minimum = INT_MIN/2;
> + sreal maximum = INT_MAX/2;
>
> sreal seven = 7;
> sreal minus_two = -2;
> sreal minus_nine = -9;
>
> - ASSERT_EQ (INT_MIN, minimum.to_int ());
> - ASSERT_EQ (INT_MAX, maximum.to_int ());
> + ASSERT_EQ (INT_MIN/2, minimum.to_int ());
> + ASSERT_EQ (INT_MAX/2, maximum.to_int ());
>
> ASSERT_FALSE (minus_two < minus_two);
> ASSERT_FALSE (seven < seven);
>
>
--
Richard Biener <rguent...@suse.de>
SUSE LINUX GmbH, GF: Felix Imendoerffer, Jane Smithard, Graham Norton, HRB
21284 (AG Nuernberg)
