diff mbox

[v2,1/2] soft-fp: Use temporary variable in FP_FRAC_SUB_3/FP_FRAC_SUB_4

Message ID bb315fd23d73811b8a391f9fe63dc83f36fa5880.1540990635.git.zongbox@gmail.com
State New
Headers show

Commit Message

Zong Li Oct. 31, 2018, 1:10 p.m. UTC
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(-)
diff mbox

Patch

diff --git a/ChangeLog b/ChangeLog
index b798b63..0cced2b 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -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
diff --git a/soft-fp/op-4.h b/soft-fp/op-4.h
index 01b87d0..b429801 100644
--- a/soft-fp/op-4.h
+++ b/soft-fp/op-4.h
@@ -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