On 24/11/13 02:14, Ian Lance Taylor wrote:
> Kugan <kugan.vivekanandara...@linaro.org> writes:
>
>> This RFC patch series implements a simple align divisor shift dividend
>> method.
>>
>> Regression tested on arm-none-linux-gnueabi with no issues.
>>
>> OK?
>>
>> Thanks,
>> Kugan
>>
>> +2013-11-22 Kugan Vivekanandarajah <kug...@linaro.org>
>> +
>> + * libgcc/libgcc2.c (__udivmoddi4): Define new implementation when
>> + HAVE_NO_HW_DIVIDE is defined, for processors without any divide
>> + instructions.
>
>
> The code looks fine to me.
>
> You should document HAVE_NO_HW_DIVIDE in gcc/doc/tm.texi in the Library
> Calls section. The macro should probably be something like
> TARGET_HAS_NO_HW_DIVIDE.
>
Thanks for the review. Is this OK for trunk now?
+2013-11-26 Kugan Vivekanandarajah <kug...@linaro.org>
+
+ * libgcc/libgcc2.c (__udivmoddi4): Define new implementation when
+ TARGET_HAS_NO_HW_DIVIDE is defined, for processors without any divide
+ instructions.
+
+2013-11-26 Kugan Vivekanandarajah <kug...@linaro.org>
+
+ * doc/tm.texi.in (TARGET_HAS_NO_HW_DIVIDE): Define.
+ * doc/tm.texi (TARGET_HAS_NO_HW_DIVIDE): Regenerate.
+
Thanks,
Kugan
diff --git a/gcc/doc/tm.texi b/gcc/doc/tm.texi
index 925d93f..c9697f1 100644
--- a/gcc/doc/tm.texi
+++ b/gcc/doc/tm.texi
@@ -5365,6 +5365,14 @@ If this macro evaluates to @code{false} the comparison
functions return
in @file{libgcc.a}, you do not need to define this macro.
@end defmac
+@defmac TARGET_HAS_NO_HW_DIVIDE
+This macro should be defined if the target has no hardware divide
+instructions. If this macro is defined, GCC will use an algorithm which
+make use of simple logical and arithmetic operations for 64-bit
+division. If the macro is not defined, GCC will use an algorithm which
+make use of a 64-bit by 32-bit divide primitive.
+@end defmac
+
@cindex @code{EDOM}, implicit usage
@findex matherr
@defmac TARGET_EDOM
diff --git a/gcc/doc/tm.texi.in b/gcc/doc/tm.texi.in
index edca600..03e6662 100644
--- a/gcc/doc/tm.texi.in
+++ b/gcc/doc/tm.texi.in
@@ -4205,6 +4205,14 @@ If this macro evaluates to @code{false} the comparison
functions return
in @file{libgcc.a}, you do not need to define this macro.
@end defmac
+@defmac TARGET_HAS_NO_HW_DIVIDE
+This macro should be defined if the target has no hardware divide
+instructions. If this macro is defined, GCC will use an algorithm which
+make use of simple logical and arithmetic operations for 64-bit
+division. If the macro is not defined, GCC will use an algorithm which
+make use of a 64-bit by 32-bit divide primitive.
+@end defmac
+
@cindex @code{EDOM}, implicit usage
@findex matherr
@defmac TARGET_EDOM
diff --git a/libgcc/libgcc2.c b/libgcc/libgcc2.c
index bec411b..8c4cc6a 100644
--- a/libgcc/libgcc2.c
+++ b/libgcc/libgcc2.c
@@ -934,6 +934,74 @@ __parityDI2 (UDWtype x)
#endif
#ifdef L_udivmoddi4
+#ifdef TARGET_HAS_NO_HW_DIVIDE
+
+#if (defined (L_udivdi3) || defined (L_divdi3) || \
+ defined (L_umoddi3) || defined (L_moddi3))
+static inline __attribute__ ((__always_inline__))
+#endif
+UDWtype
+__udivmoddi4 (UDWtype n, UDWtype d, UDWtype *rp)
+{
+ UDWtype q = 0, r = n, y = d;
+ UWtype lz1, lz2, i, k;
+
+ /* Implements align divisor shift dividend method. This algorithm
+ aligns the divisor under the dividend and then perform number of
+ test-subtract iterations which shift the dividend left. Number of
+ iterations is k + 1 where k is the number of bit positions the
+ divisor must be shifted left to align it under the dividend.
+ quotient bits can be saved in the rightmost positions of the dividend
+ as it shifts left on each test-subtract iteration. */
+
+ if (y <= r)
+ {
+ lz1 = __builtin_clzll (d);
+ lz2 = __builtin_clzll (n);
+
+ k = lz1 - lz2;
+ y = (y << k);
+
+ /* Dividend can exceed 2 ^ (width − 1) − 1 but still be less than the
+ aligned divisor. Normal iteration can drops the high order bit
+ of the dividend. Therefore, first test-subtract iteration is a
+ special case, saving its quotient bit in a separate location and
+ not shifting the dividend. */
+ if (r >= y)
+ {
+ r = r - y;
+ q = (1ULL << k);
+ }
+
+ if (k > 0)
+ {
+ y = y >> 1;
+
+ /* k additional iterations where k regular test subtract shift
+ dividend iterations are done. */
+ i = k;
+ do
+ {
+ if (r >= y)
+ r = ((r - y) << 1) + 1;
+ else
+ r = (r << 1);
+ i = i - 1;
+ } while (i != 0);
+
+ /* First quotient bit is combined with the quotient bits resulting
+ from the k regular iterations. */
+ q = q + r;
+ r = r >> k;
+ q = q - (r << k);
+ }
+ }
+
+ if (rp)
+ *rp = r;
+ return q;
+}
+#else
#if (defined (L_udivdi3) || defined (L_divdi3) || \
defined (L_umoddi3) || defined (L_moddi3))
@@ -1152,6 +1220,7 @@ __udivmoddi4 (UDWtype n, UDWtype d, UDWtype *rp)
return ww.ll;
}
#endif
+#endif
#ifdef L_divdi3
DWtype
