This patch fixes incorrect results for HOST_WIDE_INT positions
at opposite extremes when used with HOST_WIDE_INT sizes. It also
fixes UB when comparing such positions with unsigned HOST_WIDE_INT
sizes (although the results in that case were wrapv-correct).
Tested on aarch64-linux-gnu and x86_64-linux-gnu. OK to install?
Richard
2018-03-21 Richard Sandiford <richard.sandif...@linaro.org>
gcc/
PR tree-optimization/84811
* poly-int.h (poly_span_traits): Remove the T3 parameter and
promote HOST_WIDE_INT T2 - T1 results to unsigned HOST_WIDE_INT.
(maybe_in_range_p, known_in_range_p, ranges_known_overlap_p):
(known_subrange_p): Update accordingly. Cast each value involved
in the size comparison, rather than casting the result of the
subtraction.
gcc/testsuite/
PR tree-optimization/84811
* gcc.dg/torture/pr84811.c: New test.
Index: gcc/poly-int.h
===================================================================
--- gcc/poly-int.h 2018-01-14 08:42:44.497155977 +0000
+++ gcc/poly-int.h 2018-03-21 08:28:14.656720617 +0000
@@ -2399,30 +2399,34 @@ print_dec (const poly_int_pod<N, C> &val
poly_coeff_traits<C>::signedness ? SIGNED : UNSIGNED);
}
-/* Helper for correctly comparing Pos - Start with Size in cases where
- known_ge (Pos, Start), Pos and Start are potentially signed, and Size is
- potentially unsigned. Applying the cast function to the result of
- Pos - Start gives the value that should be compared with the size.
-
- Try to avoid doing any unnecessary arithmetic or copying. */
-template<typename Pos, typename Start, typename Size,
- typename Diff = POLY_BINARY_COEFF (Start, Pos),
- typename Res = POLY_BINARY_COEFF (Size, Diff)>
+/* Helper for calculating the distance between two points P1 and P2,
+ in cases where known_le (P1, P2). T1 and T2 are the types of the
+ two positions, in either order. The coefficients of P2 - P1 have
+ type unsigned HOST_WIDE_INT if the coefficients of both T1 and T2
+ have C++ primitive type, otherwise P2 - P1 has its usual
+ wide-int-based type.
+
+ The actual subtraction should look something like this:
+
+ typedef poly_span_traits<T1, T2> span_traits;
+ span_traits::cast (P2) - span_traits::cast (P1)
+
+ Applying the cast before the subtraction avoids undefined overflow
+ for signed T1 and T2.
+
+ The implementation of the cast tries to avoid unnecessary arithmetic
+ or copying. */
+template<typename T1, typename T2,
+ typename Res = POLY_BINARY_COEFF (POLY_BINARY_COEFF (T1, T2),
+ unsigned HOST_WIDE_INT)>
struct poly_span_traits
{
- /* Assume no cast is needed. We'll get a warning about signed vs.
- unsigned comparisons if the assumption is wrong. */
template<typename T>
static const T &cast (const T &x) { return x; }
};
-/* The only case a change in type is needed is this one, in which the
- subtraction would give a HOST_WIDE_INT-based result if done on poly_ints
- and adding a zero size would give an unsigned HOST_WIDE_INT-based
- result. Since we know known_ge (Pos, Start), it is safe to treat
- Pos - Start as an unsigned HOST_WIDE_INT. */
-template<typename T1, typename T2, typename T3>
-struct poly_span_traits<T1, T2, T3, HOST_WIDE_INT, unsigned HOST_WIDE_INT>
+template<typename T1, typename T2>
+struct poly_span_traits<T1, T2, unsigned HOST_WIDE_INT>
{
template<typename T>
static typename if_nonpoly<T, unsigned HOST_WIDE_INT>::type
@@ -2451,7 +2455,8 @@ known_size_p (const T &a)
inline bool
maybe_in_range_p (const T1 &val, const T2 &pos, const T3 &size)
{
- typedef poly_span_traits<T1, T2, T3> span;
+ typedef poly_span_traits<T1, T2> start_span;
+ typedef poly_span_traits<T3, T3> size_span;
if (known_lt (val, pos))
return false;
if (!known_size_p (size))
@@ -2462,7 +2467,8 @@ maybe_in_range_p (const T1 &val, const T
/* In this case we don't know whether VAL >= POS is true at compile
time, so we can't prove that VAL >= POS + SIZE. */
return true;
- return maybe_lt (span::cast (val - pos), size);
+ return maybe_lt (start_span::cast (val) - start_span::cast (pos),
+ size_span::cast (size));
}
/* Return true if range [POS, POS + SIZE) is known to include VAL.
@@ -2473,10 +2479,12 @@ maybe_in_range_p (const T1 &val, const T
inline bool
known_in_range_p (const T1 &val, const T2 &pos, const T3 &size)
{
- typedef poly_span_traits<T1, T2, T3> span;
+ typedef poly_span_traits<T1, T2> start_span;
+ typedef poly_span_traits<T3, T3> size_span;
return (known_size_p (size)
&& known_ge (val, pos)
- && known_lt (span::cast (val - pos), size));
+ && known_lt (start_span::cast (val) - start_span::cast (pos),
+ size_span::cast (size)));
}
/* Return true if the two ranges [POS1, POS1 + SIZE1) and [POS2, POS2 + SIZE2)
@@ -2504,8 +2512,9 @@ ranges_maybe_overlap_p (const T1 &pos1,
ranges_known_overlap_p (const T1 &pos1, const T2 &size1,
const T3 &pos2, const T4 &size2)
{
- typedef poly_span_traits<T1, T3, T2> span1;
- typedef poly_span_traits<T1, T3, T4> span2;
+ typedef poly_span_traits<T1, T3> start_span;
+ typedef poly_span_traits<T2, T2> size1_span;
+ typedef poly_span_traits<T4, T4> size2_span;
/* known_gt (POS1 + SIZE1, POS2) [infinite precision]
--> known_gt (SIZE1, POS2 - POS1) [infinite precision]
--> known_gt (SIZE1, POS2 - lower_bound (POS1, POS2)) [infinite precision]
@@ -2520,8 +2529,12 @@ ranges_known_overlap_p (const T1 &pos1,
which the indeterminate is zero (the minimum value). */
return (known_size_p (size1)
&& known_size_p (size2)
- && known_lt (span1::cast (pos2 - lower_bound (pos1, pos2)), size1)
- && known_lt (span2::cast (pos1 - lower_bound (pos1, pos2)), size2));
+ && known_lt (start_span::cast (pos2)
+ - start_span::cast (lower_bound (pos1, pos2)),
+ size1_span::cast (size1))
+ && known_lt (start_span::cast (pos1)
+ - start_span::cast (lower_bound (pos1, pos2)),
+ size2_span::cast (size2)));
}
/* Return true if range [POS1, POS1 + SIZE1) is known to be a subrange of
@@ -2534,15 +2547,16 @@ known_subrange_p (const T1 &pos1, const
const T3 &pos2, const T4 &size2)
{
typedef typename poly_int_traits<T2>::coeff_type C2;
- typedef POLY_BINARY_COEFF (T2, T4) size_diff_type;
- typedef poly_span_traits<T1, T3, size_diff_type> span;
+ typedef poly_span_traits<T1, T3> start_span;
+ typedef poly_span_traits<T2, T4> size_span;
return (known_gt (size1, POLY_INT_TYPE (T2) (0))
&& (poly_coeff_traits<C2>::signedness > 0
|| known_size_p (size1))
&& known_size_p (size2)
&& known_ge (pos1, pos2)
&& known_le (size1, size2)
- && known_le (span::cast (pos1 - pos2), size2 - size1));
+ && known_le (start_span::cast (pos1) - start_span::cast (pos2),
+ size_span::cast (size2) - size_span::cast (size1)));
}
/* Return true if the endpoint of the range [POS, POS + SIZE) can be
Index: gcc/testsuite/gcc.dg/torture/pr84811.c
===================================================================
--- /dev/null 2018-03-17 08:19:33.716019995 +0000
+++ gcc/testsuite/gcc.dg/torture/pr84811.c 2018-03-21 08:28:14.660640089
+0000
@@ -0,0 +1,20 @@
+/* { dg-do compile { target lp64 } } */
+
+int a;
+long b[1][9];
+typedef long V __attribute__((vector_size (16), may_alias));
+
+void
+foo ()
+{
+ V *c = (V *) ((char *) b + -9060696663385964544);
+ *c = (V) { 1, 1 };
+ c++;
+ *c = (V) { 1, 1 };
+ c++;
+ *c = (V) { 1, 1 };
+ c++;
+ *c = (V) { 1, 1 };
+ long __attribute__((may_alias)) *d = (long *) ((char *) b +
162675373468811328);
+ *d = 1;
+}
