[PATCH v2 07/28] Add umul_ppmm to gmp-arch.hdoc

[Adhemerval Zanella]

To enable “longlong.h” removal, the umul_ppmm is moved to a gmp-arch.h.
The generic implementation now uses a static inline, which provides
better type checking than the GNU extension to cast the asm constraint
(and it works better with clang).

Most of the architecture uses the generic implementation, which is
expanded from a macro, except for alpha, arm, hppa, x86, m68k, mips,
powerpc, and sparc.  I kept only x86 optimization, where there is no
easy way to emit mul{q}. For the rest, the compiler generates good
enough code.
---
 sysdeps/generic/gmp-arch.h | 40 ++++++++++++++++++++++++++++++++++++++
 sysdeps/x86/gmp-arch.h     | 21 ++++++++++++++++++++
 2 files changed, 61 insertions(+)

diff --git a/sysdeps/generic/gmp-arch.h b/sysdeps/generic/gmp-arch.h
index 3ec144562a..f5d6495f2b 100644
--- a/sysdeps/generic/gmp-arch.h
+++ b/sysdeps/generic/gmp-arch.h
@@ -35,6 +35,46 @@ ll_highpart (mp_limb_t t)
   return t >> (BITS_PER_MP_LIMB / 2);
 }
 
+/* umul_ppmm(high_prod, low_prod, multiplier, multiplicand) multiplies two
+   UWtype integers MULTIPLIER and MULTIPLICAND, and generates a two UWtype
+   word product in HIGH_PROD and LOW_PROD.  */
+static __always_inline void
+umul_ppmm_generic (mp_limb_t *w1, mp_limb_t *w0, mp_limb_t u, mp_limb_t v)
+{
+#if __WORDSIZE == 32
+  uint64_t t0 = (uint64_t)u * v;
+  *w1 = t0 >> 32;
+  *w0 = t0;
+#else
+  mp_limb_t ul = ll_lowpart (u);
+  mp_limb_t uh = ll_highpart (u);
+  mp_limb_t vl = ll_lowpart (v);
+  mp_limb_t vh = ll_highpart (v);
+
+  mp_limb_t x0 = ul * vl;
+  mp_limb_t x1 = ul * vh;
+  mp_limb_t x2 = uh * vl;
+  mp_limb_t x3 = uh * vh;
+
+  x1 += ll_highpart (x0);
+  x1 += x2;
+  if (x1 < x2)
+    x3 += LL_B;
+
+  *w1 = x3 + ll_highpart (x1);
+  *w0 = ll_lowpart (x1) * LL_B + ll_lowpart (x0);
+#endif
+}
+#undef umul_ppmm
+#define umul_ppmm(__w1, __w0, __u, __v)			\
+  ({							\
+    __typeof (__w0) __w0t;				\
+    __typeof (__w1) __w1t;				\
+    umul_ppmm_generic (&__w1t, &__w0t, __u, __v);	\
+    __w1 = __w1t;					\
+    __w0 = __w0t;					\
+  })
+
 /* udiv_qrnnd(quotient, remainder, high_numerator, low_numerator,
    denominator) divides a UDWtype, composed by the UWtype integers
    HIGH_NUMERATOR and LOW_NUMERATOR, by DENOMINATOR and places the quotient
diff --git a/sysdeps/x86/gmp-arch.h b/sysdeps/x86/gmp-arch.h
index 45f047e1b6..c3aa0f2e3b 100644
--- a/sysdeps/x86/gmp-arch.h
+++ b/sysdeps/x86/gmp-arch.h
@@ -21,6 +21,27 @@
 
 #include <gmp.h>
 
+static __always_inline void
+umul_ppmm_generic (mp_limb_t *w1, mp_limb_t *w0, mp_limb_t u, mp_limb_t v)
+{
+#ifdef __x86_64__
+  asm ("mul{q} %3"
+       : "=a" (*w0),
+         "=d" (*w1)
+       : "%0" (u),
+         "rm" (v));
+#else
+  asm ("mul{l} %3"
+       : "=a" (*w0),
+         "=d" (*w1)
+       : "%0" (u),
+         "rm" (v));
+#endif
+}
+#undef umul_ppmm
+#define umul_ppmm(__w1, __w0, __u, __v) \
+  umul_ppmm_generic (&__w1, &__w0, __u, __v)
+
 static __always_inline void
 udiv_qrnnd_x86 (mp_limb_t *q, mp_limb_t *r, mp_limb_t n1, mp_limb_t n0,
 		mp_limb_t d)
-- 
2.43.0