[v2,1/2] soft-fp: Use temporary variable in FP_FRAC_SUB_3/FP_FRAC_SUB_4
Commit Message
In FRAC_SUB_3(R, X, Y) and FRAC_SUB_4(R,, X, Y), it reference both
the X[N] and X[N] after R[N] have been set. If one of the X and Y is
the same address with R, the result of the calculation is wrong,
because the value of the original X and Y are overwritten.
In glibc, there are two places use FRAC_SUB and occurs the overlap.
The first is _FP_DIV_MEAT_N_loop in op-common.h, it uses the source
_FP_DIV_MEAT_N_loop_u as the destination. This macro only be used
when N is one(_FP_DIV_MEAT_1_loop) and then the _FP_FRAC_SUB_##wc
extend to _FP_FRAC_SUB_1 in this macro. so it also work because
_FP_FRAC_SUB_1 has no overlap problem in its implementation.
The second places is _FP_DIV_MEAT_4_udiv, the original value of X##_f[0]
is overwritten before the calculatation.
In FRAC_SUB_1 and FRAC_SUB_2, there don't refer the source after
destination have been set, so they have no problem.
After this modification, we can pass the soft floating testing of glibc
testsuites on RV32.
* soft-fp/op-4.h (_FP_FRAC_SUB_3, _FP_FRAC_SUB_4): Use temporary
variable to avoid overlap arguments.
---
ChangeLog | 5 +++++
soft-fp/op-4.h | 63 ++++++++++++++++++++++++++++++++--------------------------
2 files changed, 40 insertions(+), 28 deletions(-)
@@ -1,3 +1,8 @@
+2018-10-31 Zong Li <zong@andestech.com>
+
+ * soft-fp/op-4.h (_FP_FRAC_SUB_3, _FP_FRAC_SUB_4): Use temporary
+ variable to avoid overlap arguments.
+
2018-10-31 Samuel Thibault <samuel.thibault@ens-lyon.org>
* manual/errno.texi (EIEIO): Document how translators should
@@ -696,39 +696,46 @@
#endif
#ifndef __FP_FRAC_SUB_3
-# define __FP_FRAC_SUB_3(r2, r1, r0, x2, x1, x0, y2, y1, y0) \
- do \
- { \
- _FP_W_TYPE __FP_FRAC_SUB_3_c1, __FP_FRAC_SUB_3_c2; \
- r0 = x0 - y0; \
- __FP_FRAC_SUB_3_c1 = r0 > x0; \
- r1 = x1 - y1; \
- __FP_FRAC_SUB_3_c2 = r1 > x1; \
- r1 -= __FP_FRAC_SUB_3_c1; \
- __FP_FRAC_SUB_3_c2 |= __FP_FRAC_SUB_3_c1 && (y1 == x1); \
- r2 = x2 - y2 - __FP_FRAC_SUB_3_c2; \
- } \
+# define __FP_FRAC_SUB_3(r2, r1, r0, x2, x1, x0, y2, y1, y0) \
+ do \
+ { \
+ _FP_W_TYPE __FP_FRAC_SUB_3_tmp[2]; \
+ _FP_W_TYPE __FP_FRAC_SUB_3_c1, __FP_FRAC_SUB_3_c2; \
+ __FP_FRAC_SUB_3_tmp[0] = x0 - y0; \
+ __FP_FRAC_SUB_3_c1 = __FP_FRAC_SUB_3_tmp[0] > x0; \
+ __FP_FRAC_SUB_3_tmp[1] = x1 - y1; \
+ __FP_FRAC_SUB_3_c2 = __FP_FRAC_SUB_3_tmp[1] > x1; \
+ __FP_FRAC_SUB_3_tmp[1] -= __FP_FRAC_SUB_3_c1; \
+ __FP_FRAC_SUB_3_c2 |= __FP_FRAC_SUB_3_c1 && (y1 == x1); \
+ r2 = x2 - y2 - __FP_FRAC_SUB_3_c2; \
+ r1 = __FP_FRAC_SUB_3_tmp[1]; \
+ r0 = __FP_FRAC_SUB_3_tmp[0]; \
+ } \
while (0)
#endif
#ifndef __FP_FRAC_SUB_4
# define __FP_FRAC_SUB_4(r3, r2, r1, r0, x3, x2, x1, x0, y3, y2, y1, y0) \
- do \
- { \
- _FP_W_TYPE __FP_FRAC_SUB_4_c1, __FP_FRAC_SUB_4_c2; \
- _FP_W_TYPE __FP_FRAC_SUB_4_c3; \
- r0 = x0 - y0; \
- __FP_FRAC_SUB_4_c1 = r0 > x0; \
- r1 = x1 - y1; \
- __FP_FRAC_SUB_4_c2 = r1 > x1; \
- r1 -= __FP_FRAC_SUB_4_c1; \
- __FP_FRAC_SUB_4_c2 |= __FP_FRAC_SUB_4_c1 && (y1 == x1); \
- r2 = x2 - y2; \
- __FP_FRAC_SUB_4_c3 = r2 > x2; \
- r2 -= __FP_FRAC_SUB_4_c2; \
- __FP_FRAC_SUB_4_c3 |= __FP_FRAC_SUB_4_c2 && (y2 == x2); \
- r3 = x3 - y3 - __FP_FRAC_SUB_4_c3; \
- } \
+ do \
+ { \
+ _FP_W_TYPE __FP_FRAC_SUB_4_tmp[3]; \
+ _FP_W_TYPE __FP_FRAC_SUB_4_c1, __FP_FRAC_SUB_4_c2; \
+ _FP_W_TYPE __FP_FRAC_SUB_4_c3; \
+ __FP_FRAC_SUB_4_tmp[0] = x0 - y0; \
+ __FP_FRAC_SUB_4_c1 = __FP_FRAC_SUB_4_tmp[0] > x0; \
+ __FP_FRAC_SUB_4_tmp[1] = x1 - y1; \
+ __FP_FRAC_SUB_4_c2 = __FP_FRAC_SUB_4_tmp[1] > x1; \
+ __FP_FRAC_SUB_4_tmp[1] -= __FP_FRAC_SUB_4_c1; \
+ __FP_FRAC_SUB_4_c2 |= __FP_FRAC_SUB_4_c1 && (y1 == x1); \
+ __FP_FRAC_SUB_4_tmp[2] = x2 - y2; \
+ __FP_FRAC_SUB_4_c3 = __FP_FRAC_SUB_4_tmp[2] > x2; \
+ __FP_FRAC_SUB_4_tmp[2] -= __FP_FRAC_SUB_4_c2; \
+ __FP_FRAC_SUB_4_c3 |= __FP_FRAC_SUB_4_c2 && (y2 == x2); \
+ r3 = x3 - y3 - __FP_FRAC_SUB_4_c3; \
+ r2 = __FP_FRAC_SUB_4_tmp[2]; \
+ r1 = __FP_FRAC_SUB_4_tmp[1]; \
+ r0 = __FP_FRAC_SUB_4_tmp[0]; \
+ } \
while (0)
#endif