From 535808fd722db576f0f14424bc083fbef183fd4b Mon Sep 17 00:00:00 2001 From: Richard Sandiford Date: Wed, 21 Mar 2018 20:52:15 +0000 Subject: [PATCH] poly_span_traits fixes (PR 84811) 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). 2018-03-20 Richard Sandiford 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. From-SVN: r258743 --- gcc/ChangeLog | 10 ++++ gcc/poly-int.h | 72 +++++++++++++++----------- gcc/testsuite/ChangeLog | 5 ++ gcc/testsuite/gcc.dg/torture/pr84811.c | 20 +++++++ 4 files changed, 78 insertions(+), 29 deletions(-) create mode 100644 gcc/testsuite/gcc.dg/torture/pr84811.c diff --git a/gcc/ChangeLog b/gcc/ChangeLog index 0980eac591d..2c5ed01e3f4 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,3 +1,13 @@ +2018-03-21 Richard Sandiford + + 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. + 2018-03-21 Jakub Jelinek PR tree-optimization/84982 diff --git a/gcc/poly-int.h b/gcc/poly-int.h index 548fc64184e..62c39507952 100644 --- a/gcc/poly-int.h +++ b/gcc/poly-int.h @@ -2399,30 +2399,34 @@ print_dec (const poly_int_pod &value, FILE *file) poly_coeff_traits::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 +/* 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 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 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 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 -struct poly_span_traits +template +struct poly_span_traits { template static typename if_nonpoly::type @@ -2451,7 +2455,8 @@ template inline bool maybe_in_range_p (const T1 &val, const T2 &pos, const T3 &size) { - typedef poly_span_traits span; + typedef poly_span_traits start_span; + typedef poly_span_traits 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 T2 &pos, const T3 &size) /* 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 @@ template inline bool known_in_range_p (const T1 &val, const T2 &pos, const T3 &size) { - typedef poly_span_traits span; + typedef poly_span_traits start_span; + typedef poly_span_traits 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 @@ inline bool ranges_known_overlap_p (const T1 &pos1, const T2 &size1, const T3 &pos2, const T4 &size2) { - typedef poly_span_traits span1; - typedef poly_span_traits span2; + typedef poly_span_traits start_span; + typedef poly_span_traits size1_span; + typedef poly_span_traits 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, const T2 &size1, 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 T2 &size1, const T3 &pos2, const T4 &size2) { typedef typename poly_int_traits::coeff_type C2; - typedef POLY_BINARY_COEFF (T2, T4) size_diff_type; - typedef poly_span_traits span; + typedef poly_span_traits start_span; + typedef poly_span_traits size_span; return (known_gt (size1, POLY_INT_TYPE (T2) (0)) && (poly_coeff_traits::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 diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog index f12a38357bb..36e16266c00 100644 --- a/gcc/testsuite/ChangeLog +++ b/gcc/testsuite/ChangeLog @@ -1,3 +1,8 @@ +2018-03-21 Richard Sandiford + + PR tree-optimization/84811 + * gcc.dg/torture/pr84811.c: New test. + 2018-03-21 Jakub Jelinek PR tree-optimization/84982 diff --git a/gcc/testsuite/gcc.dg/torture/pr84811.c b/gcc/testsuite/gcc.dg/torture/pr84811.c new file mode 100644 index 00000000000..7cf7cf2cbcd --- /dev/null +++ b/gcc/testsuite/gcc.dg/torture/pr84811.c @@ -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; +} -- 2.30.2